The Northwestern Mediterranean Sea is undergoing rapid environmental changes driven by climate variability and intense anthropogenic pressure. To monitor and understand the long-term impacts on marine ecosystems, the Mediterranean Ocean Observing System for the Environment (MOOSE) program combines multidisciplinary observations, including physical, chemical, and biological data across temporal and spatial scales. This study presents a holistic assessment of planktonic communities across the Northwestern Mediterranean using integrated approaches—environmental genomics and high-resolution imaging—spanning all plankton size fractions and depths. Data collected during three MOOSE-GE cruises in 2017, 2018, and 2019 were analyzed to explore plankton diversity patterns in relation to oceanographic features. Plankton assemblages were primarily shaped by organism size and water column depth, with fractions of 0.2–3 and 3–180 µm in the surface and deep chlorophyll maximum layers showing the highest alpha diversity. Fractions > 64 µm were dominated by metazoans, particularly Arthropoda, whereas size classes collected by Niskin bottles were dominated by protists such as Syndiniales and Rhizaria. Differences among cruises and sampling periods were detected in Niskin bottle samples, especially for diatoms and dinoflagellates, while plankton tow samples exhibited less pronounced temporal variability. Physical clustering of stations revealed clear cross-shelf and basin-scale gradients, which aligned more closely with community structure at fine taxonomic resolution (OTU level) for small plankton. Integrating imaging with environmental genomic data enhanced the characterization of key taxa like Copepoda and Rhizaria, demonstrating the complementary strengths of each method. While imaging provided quantitative data, environmental genomics captured cryptic and morphologically indistinct taxa, emphasizing the value of molecular approaches for microbial plankton. This study highlights the critical importance of combining high-resolution molecular and imaging tools with detailed environmental context to unravel plankton biodiversity patterns. It demonstrates that depth, size, and taxonomic resolution are key dimensions for understanding community structure over time. The MOOSE program proves effective for ecosystem-scale monitoring, providing an essential foundation for future assessments of biogeochemical processes and ecosystem responses to climate change and human-induced alterations in the Mediterranean Sea.

Abstract Coral reefs are marine biodiversity hotspots that provide a wide range of ecosystem services 1 . They are reservoirs of bioactive metabolites, many produced by microorganisms associated with reef invertebrate hosts 2 . However, for the keystone species of coral reefs—the reef-building corals—we still lack a systematic assessment of their microbially encoded biosynthetic potential and the molecular resources at stake due to the alarming decline in reef biodiversity. Here we analysed microbial genomes reconstructed from 820 reef-building coral samples of three representative coral genera collected at 99 reefs across 32 islands throughout the Pacific Ocean ( Tara Pacific expedition) 3 . By contextualizing our analyses with the microbiomes of other reef species, we found that only 10% of the 4,224 microbial species and less than 1% of the 645 species exclusively identified in Tara Pacific samples had genomic information available. Furthermore, the biosynthetic potential of reef-building coral microbiomes rivalled or surpassed that of traditional natural product sources such as sponges. Among the biosynthetically rich bacteria in the reef microbiome, we identified new groups of Acidobacteriota that encode previously unknown enzymology, in turn opening promising avenues for functional protein engineering. Together, this study underscores the importance of conserving coral reefs as vital reservoirs of molecular diversity.

Abstract The use of trait-based approaches and trait data in zooplankton ecology is rapidly growing to better understand and predict the patterns of zooplankton distributions and their role in aquatic ecosystems and biogeochemical cycles. Although the number of zooplankton trait-based studies and available trait datasets is increasing, several challenges remain for the findability, accessibility, interoperability, and reusability (FAIR) in trait-based approaches that, if unaddressed, may stifle progress in this research area. Here, we review recent applications of trait-based approaches in zooplankton research and summarize the currently available trait data resources. To realize the potential of trait-based approaches to resolve ecological roles of zooplankton, datasets and approaches must adhere to FAIR principles. We provide recommendations and pathways forward to ensure FAIRness while highlighting the importance of collaborative efforts. These practical and easily implementable strategies will enhance the FAIRness of trait data, ultimately advancing zooplankton ecological research and connecting these findings to aquatic ecosystem functioning.

Abstract Gelatinous zooplankton are an important component of many ecosystems and important for ecosystem structure and carbon cycling. However, this group is generally not considered in biogeochemical models. Here we investigate the biomass‐to‐volume ratio as an underappreciated “master trait” that allows for the incorporation of a large diversity of zooplankton groups into modeling exercises. By considering the biomass‐to‐volume ratio as a continuum, we investigate the potential trade‐offs between body composition and physiological (e.g., clearance, respiration, carbon mass‐specific growth, assimilation) as well as ecological (e.g., predator–prey size ratio, feeding modes) traits. We find that a low carbon composition has a positive effect on the organism's fitness, as more prey could be captured for the same active mass. Thus, taking the biomass‐to‐volume ratio into account could improve the estimation of physiological rates. Additionally, we show that gelatinous feeding‐current feeders (e.g., tunicata, Mnemiopsis spp., Rhizostoma spp.) have an ability to catch smaller prey over a wider size range than non‐gelatinous feeding‐current feeding organisms (gelatinous feeding‐current feeders min–max: 10 2 –10 6 μ m predator μ m prey −1 ; non‐gelatinous feeding‐current feeders min–max: 5 × 10 0 –8 × 10 1 μ m predator μ m prey −1 ). However, results are only valid for the respective feeding mode, highlighting new trade‐offs. This allows us to re‐evaluate the functional role of certain organisms, such as larvaceans (appendicularians), which were previously considered to be super‐filters, or pteropods, which remain understudied. This study contributes to a wider representation of the complexity of the zooplankton community in size‐structured models. We highlight that the biomass‐to‐volume ratio, along with size, is the most important parameter required to represent the full diversity of zooplankton.

Abstract Marine plankton are key drivers of ocean productivity and global carbon cycling, yet their quantitative biogeography remains poorly characterized. Environmental genomic datasets are inherently compositional, restricting analyses to relative abundances and limiting their integration into ecological and biogeochemical models. Here we combine DNA mass measurements, filtered seawater volumes, and metagenomic relative abundances to generate absolute estimates of cell concentrations and carbon biomass of plankton across the global ocean. Leveraging thousands of samples, this approach provides quantitative estimates for hundreds of eukaryotic and thousands of prokaryotic environmental genomes, unveiling ecological associations not captured by compositional data. Using the psbO marker gene, we reconstruct quantitative biogeographies of photosynthetic lineages and, through global-scale modeling, project their distributions to generate quantitative maps of phytoplankton communities across the world’s ocean. By bridging genomic data with biogeochemical metrics, this study provides novel resources for integrating plankton at genomic resolution into next-generation biogeochemical models.

Abstract. This paper presents the quantitative imaging datasets collected during the Tara Pacific expedition (2016–2018) carried out on the schooner Tara. The datasets cover a wide range of plankton sizes, from microphytoplankton (> 20 µm in size) to mesozooplankton (a few centimetres in size), and non-living particles such as plastic and detrital particles. It consists of surface samples collected across the North Atlantic and the North and South Pacific Ocean from open-ocean stations (a total of 357 samples) and from stations located in coastal waters, lagoons or reefs of 32 Pacific islands (a total of 228 samples). As this expedition involved long distances and long sailing times, we designed two sampling systems to collect plankton while sailing at speeds of up to 9 knots. To sample microplankton, surface water was pumped aboard using a customised pumping system and filtered through a 20 µm mesh size plankton net (hereafter referred to as the deck net – DN). A high-speed net (HSN; 330 µm mesh size) was developed to sample the mesoplankton. In addition, a manta net (330 µm) was also used, when possible, to collect mesoplankton and plastics simultaneously. We could not deploy these nets at the reef and lagoon stations of islands. Instead, two bongo nets (20 µm) attached to an underwater scooter were used to sample microplankton. In addition to describing and presenting the datasets, the complementary aim of this paper is to investigate and quantify the potential sampling biases associated with these two high-speed sampling systems and the different net types, in order to improve further ecological interpretations. Regarding the imaging techniques, microplankton (20–200 µm) from the DN and bongo net were imaged directly aboard Tara using a FlowCam instrument (Fluid Imaging Technologies), whereas mesoplankton (>200 µm) from the HSN and manta net were analysed in the laboratory with a ZooScan system (back on land). Organisms and other particles were taxonomically and morphologically classified using the automatic sorting tools of the EcoTaxa web application; following this, validation or correction was carried out by taxonomic experts. For microplankton smaller than 45 µm, a subsample of 30 % of the annotations was 100 % visually validated by experts. More than 300 different taxonomic and morphological groups were identified. The datasets include the metadata and the raw data from which morphological traits such as size (equivalent spherical diameter) and biovolume were calculated for each particle as well as a number of quantitative descriptors of the surface plankton communities. These descriptors include abundance, biovolumes, the Shannon diversity index and normalised biovolume size spectrum, allowing the study of their structures (e.g. taxonomic, functional, size and trophic structures) according to a wide range of environmental parameters at the basin scale (https://doi.org/10.5281/zenodo.6445609, Lombard et al., 2023).

Abstract. This paper presents the quantitative imaging datasets collected during the Tara Pacific expedition (2016–2018) carried out on the schooner Tara. The datasets cover a wide range of plankton sizes, from microphytoplankton (> 20 µm in size) to mesozooplankton (a few centimetres in size), and non-living particles such as plastic and detrital particles. It consists of surface samples collected across the North Atlantic and the North and South Pacific Ocean from open-ocean stations (a total of 357 samples) and from stations located in coastal waters, lagoons or reefs of 32 Pacific islands (a total of 228 samples). As this expedition involved long distances and long sailing times, we designed two sampling systems to collect plankton while sailing at speeds of up to 9 knots. To sample microplankton, surface water was pumped aboard using a customised pumping system and filtered through a 20 µm mesh size plankton net (hereafter referred to as the deck net – DN). A high-speed net (HSN; 330 µm mesh size) was developed to sample the mesoplankton. In addition, a manta net (330 µm) was also used, when possible, to collect mesoplankton and plastics simultaneously. We could not deploy these nets at the reef and lagoon stations of islands. Instead, two bongo nets (20 µm) attached to an underwater scooter were used to sample microplankton. In addition to describing and presenting the datasets, the complementary aim of this paper is to investigate and quantify the potential sampling biases associated with these two high-speed sampling systems and the different net types, in order to improve further ecological interpretations. Regarding the imaging techniques, microplankton (20–200 µm) from the DN and bongo net were imaged directly aboard Tara using a FlowCam instrument (Fluid Imaging Technologies), whereas mesoplankton (>200 µm) from the HSN and manta net were analysed in the laboratory with a ZooScan system (back on land). Organisms and other particles were taxonomically and morphologically classified using the automatic sorting tools of the EcoTaxa web application; following this, validation or correction was carried out by taxonomic experts. For microplankton smaller than 45 µm, a subsample of 30 % of the annotations was 100 % visually validated by experts. More than 300 different taxonomic and morphological groups were identified. The datasets include the metadata and the raw data from which morphological traits such as size (equivalent spherical diameter) and biovolume were calculated for each particle as well as a number of quantitative descriptors of the surface plankton communities. These descriptors include abundance, biovolumes, the Shannon diversity index and normalised biovolume size spectrum, allowing the study of their structures (e.g. taxonomic, functional, size and trophic structures) according to a wide range of environmental parameters at the basin scale (https://doi.org/10.5281/zenodo.6445609, Lombard et al., 2023).

Since 2004, the Service facility SNAPO-CO2 (Service National d’Analyse des Paramètres Océaniques du CO2) housed by the LOCEAN laboratory (Paris, France) has been in charge for the analysis of Total Alkalinity (AT) and Total dissolved inorganic carbon (CT) of seawater samples on a series of cruises or ships of opportunity conducted in different regions in the frame of French projects. More than 44000 observations are synthetized in this work. Sampling was performed either from CTD-Rosette casts (Niskin bottles) or collected from the ship’s seawater supply (intake at about 5m depth). After completion of each cruise, discrete samples were returned back at LOCEAN laboratory and stored in a dark room at 4 °C before analysis generally within 2-3 months after sampling (sometimes within a week). AT and CT were analyzed simultaneously by potentiometric titration using a closed cell (Edmond, 1970). Certified Reference Materials (CRMs) provided by Pr. A. Dickson (Scripps Institution of Oceanography, San Diego, USA) were used to calibrate the measurements. The same instrumentation was used for underway measurements during OISO cruises (https://doi.org/10.18142/228) and OISO AT-CT data for 1998-2018 in the South Indian Ocean added in this synthesis. The synthesis is organized in two files (one for Global ocean and the Coastal Zones, one for the Mediterranean Sea) with the same format: Cruise name, Ship name, day, month, year, hour, minute, second, latitude, longitude, depth, AT (µmol/kg), Flag-AT, CT (µmol/kg), Flag-CT, Temperature (°C), Flag-Temp, Salinity (PSU), Flag-Salinity, nsample/cruise, nsample on file, sampling method.

Plastics are offering a new niche for microorganisms colonizing their surface, the so-called “plastisphere,” in which diversity and community structure remain to be characterized and compared across ocean pelagic regions. Here, we compared the bacterial diversity of microorganisms living on plastic marine debris (PMD) and the surrounding free-living (FL) and organic particle-attached (PA) lifestyles sampled during the Tara expeditions in two of the most plastic polluted zones in the world ocean, i.e., the North Pacific gyre and the Mediterranean Sea. The 16S rRNA gene sequencing analysis confirmed that PMD are a new anthropogenic ocean habitat for marine microbes at the ocean-basin-scale, with clear niche partitioning compared to FL and PA lifestyles. At an ocean-basin-scale, the composition of the plastisphere communities was mainly driven by environmental selection, rather than polymer types or dispersal effect. A plastisphere “core microbiome” could be identified, mainly dominated by Rhodobacteraceae and Cyanobacteria. Predicted functions indicated the dominance of carbon, nitrogen and sulfur metabolisms on PMD that open new questions on the role of the plastisphere in a large number of important ecological processes in the marine ecosystem.

Abstract. Total alkalinity (AT) and dissolved inorganic carbon (CT) in the oceans are important properties with respect to understanding the ocean carbon cycle and its link to global change (ocean carbon sinks and sources, ocean acidification) and ultimately finding carbon-based solutions or mitigation procedures (marine carbon removal). We present a database of more than 44 400 AT and CT observations along with basic ancillary data (spatiotemporal location, depth, temperature and salinity) from various ocean regions obtained, mainly in the framework of French projects, since 1993. This includes both surface and water column data acquired in the open ocean, coastal zones and in the Mediterranean Sea and either from time series or dedicated one-off cruises. Most AT and CT data in this synthesis were measured from discrete samples using the same closed-cell potentiometric titration calibrated with Certified Reference Material, with an overall accuracy of ±4 µmol kg−1 for both AT and CT. The data are provided in two separate datasets – for the Global Ocean and the Mediterranean Sea (https://doi.org/10.17882/95414, Metzl et al., 2023), respectively – that offer a direct use for regional or global purposes, e.g., AT–salinity relationships, long-term CT estimates, and constraint and validation of diagnostic CT and AT reconstructed fields or ocean carbon and coupled climate–carbon models simulations as well as data derived from Biogeochemical-Argo (BGC-Argo) floats. When associated with other properties, these data can also be used to calculate pH, the fugacity of CO2 (fCO2) and other carbon system properties to derive ocean acidification rates or air–sea CO2 fluxes.

<p>Massive reef-building Porites corals are commonly studied to obtain long-term reconstructions of past sea surface temperature (SST) using temperature-sensitive elemental proxies, such as Sr/Ca or Li/Mg ratios. Most recently, a multi-proxy approach combining these two ratios (e.g. D'Olivo et al., 2018) and the Srsingle bondU method (DeCarlo et al., 2016) have proved to be more robust to reconstruct paleo-temperatures. To date, no study has been carried out on the application of these new approaches on the Diploastrea heliopora coral, another massive reef-building genus that can potentially provide longer temperature records. Moreover, only a few studies have assessed coral SST calibrations at the scale of the Indo-Pacific basin and compared SST reconstructions obtained from two massive coral genera from the same site. In this study, we investigated the elemental composition of the topmost portion of 34 modern tropical Porites and 6 Diploastrea colonies collected during the Tara Pacific expedition (2016–2018) from various hydrological contexts in the Pacific Ocean. We derived and discussed annual Sr/Ca, Li/Mg, combined Sr/Ca-Li/Mg and Sr/Ca-Li/Ca-Mg/Ca and Srsingle bondU vs. SST calibrations as well as potential intra-colonial and genus specific effects and evaluated the use of these basin-wide calibration equations. Overall, multi-ratio and multi-genera SST calibrations perform better than single-ratio calibrations and seem to improve temperature reconstructions. These new SST calibrations were applied to two colonies of Porites and Diploastrea collected from the same site in the North-West of the Palau archipelago located in the western Pacific Ocean to evaluate the applicability of universal calibrations based on different proxies and their combination. Coral-based SST records spanning the last 141 years show decadal changes and recent warming episodes that are related to major El Niño Southern Oscillation events. However, differences in reconstruction remain between both genera in the long-term trends, amplitudes, and absolute temperatures, depending on which genus or temperature proxy is considered.</p>

Since most physiological, ecological, or physical processes in marine ecosystems are size-dependent, plankton size spectra are important indicators of the efficiency of the biological carbon pump and other plankton-mediated fluxes. Global predictions of plankton size spectra have recently started to integrate direct size measurements provided by imaging sensors, albeit they currently do not resolve plankton diversity within their size distributions. Using imaging datasets recently compiled as part of the Pelagic Size Structure database initiative (https://pssdb.net/), we investigate the size distribution of numerically important taxa at the global scale. More specifically, we assessed the size spectra of Rhizarians, Crustaceans and colonial N2 fixers and explored their relationships with environmental factors. We found strong linkages between temperature and the size structure of all the groups, but individual responses to iron acquisition or mesoscale circulation helped distinguish specific niches within the plankton community. We used these responses to predict the biogeography of different plankton groups, each showing good agreement with independent observations. Such analysis should help constrain the stocks (i.e. integral of the size spectrum) and the roles of these significant actors of marine biogeochemical cycles with respect to various ecological and biogeochemical processes.

Abstract. In marine ecosystems, most physiological, ecological, or physical processes are size dependent. These include metabolic rates, the uptake of carbon and other nutrients, swimming and sinking velocities, and trophic interactions, which eventually determine the stocks of commercial species, as well as biogeochemical cycles and carbon sequestration. As such, broad-scale observations of plankton size distribution are important indicators of the general functioning and state of pelagic ecosystems under anthropogenic pressures. Here, we present the first global datasets of the Pelagic Size Structure database (PSSdb), generated from plankton imaging devices. This release includes the bulk particle normalized biovolume size spectrum (NBSS) and the bulk particle size distribution (PSD), along with their related parameters (slope, intercept, and R2) measured within the epipelagic layer (0–200 m) by three imaging sensors: the Imaging FlowCytobot (IFCB), the Underwater Vision Profiler (UVP), and benchtop scanners. Collectively, these instruments effectively image organisms and detrital material in the 7–10 000 µm size range. A total of 92 472 IFCB samples, 3068 UVP profiles, and 2411 scans passed our quality control and were standardized to produce consistent instrument-specific size spectra averaged to 1° × 1° latitude and longitude and by year and month. Our instrument-specific datasets span most major ocean basins, except for the IFCB datasets we have ingested, which were exclusively collected in northern latitudes, and cover decadal time periods (2013–2022 for IFCB, 2008–2021 for UVP, and 1996–2022 for scanners), allowing for a further assessment of the pelagic size spectrum in space and time. The datasets that constitute PSSdb's first release are available at https://doi.org/10.5281/zenodo.11050013 (Dugenne et al., 2024b). In addition, future updates to these data products can be accessed at https://doi.org/10.5281/zenodo.7998799.

Abstract. This paper presents the quantitative imaging datasets collected during the Tara Pacific Expedition (2016–2018) on the schooner Tara. The datasets cover a wide range of plankton sizes, from micro-phytoplankton > 20 μm to meso-zooplankton of a few cm, as well as non-living particles such as plastic and detrital particles. It consists of surface samples collected across the North and South Pacific Ocean from open ocean stations (a total of 357 samples) and from stations located in coastal waters, lagoons or reefs of 32 Pacific islands (a total of 228 samples). As this expedition involved long distances and long sailing times, we designed two sampling systems to collect plankton while sailing at speeds up to 9 knots. To sample microplankton, surface water was pumped onboard using a customised pumping system and filtered through a 20 µm mesh size plankton net (here after Deck-Net (DN). A High Speed Net (HSN; 330 μm mesh size) was developed to sample the mesoplankton. In addition, a Manta net (330 µm) was also used when possible, to collect mesoplankton and plastics simultaneously. We could not deploy these nets in reef and lagoon stations of islands. Instead, two Bongo nets (20 µm) attached to an underwater scooter were used to sample microplankton. Microplankton (20–200 μm) from the DN and Bongo nets was imaged directly on-board Tara using the FlowCam (Fluid imaging, Inc.) while the mesoplankton (> 200 μm) from the HSN and Manta nets was analyzed in the laboratory with the ZooScan system. Organisms and other particles were taxonomically and morphologically classified using the web application EcoTaxa automatic sorting tools, followed by taxonomic expert validation or correction. More than 300 different taxonomic and morphological groups were identified. The datasets include the metadata with the raw data from which morphological traits such as size (ESD) and biovolume have been calculated for each particle, as well as a number of quantitative descriptors of the surface plankton communities. These include abundance, biovolumes, Shannon diversity index and normalised biovolume size spectra, allowing the study of their structures (e.g. taxonomic, functional, size structure, trophic structure, etc.) according to a wide range of environmental parameters at the basin scale. In addition to describing and presenting the datasets, the complementary aim of this paper is to investigate and quantify the potential sampling biases associated with the two high speed sampling systems and the different net types, in order to improve further ecological interpretations.

Summary paragraph Plankton are essential in marine ecosystems. However, our knowledge of overall community structure is sparse due to inconsistent sampling across their very large organismal size range. Here we use diverse imaging methods to establish complete plankton inventories of organisms spanning five orders of magnitude in size. Plankton community size and trophic structure variation validate a long-held theoretical link between organism size-spectra and ecosystem trophic structures. We found that predator/grazer biomass and biovolume unexpectedly exceed that of primary producers at most (55%) locations, likely due to our better quantification of gelatinous organisms. Bottom- heavy ecosystems (the norm on land) appear to be rare in the ocean. Collectively, gelatinous organisms represent 30% of the total biovolume (8-9% of carbon) of marine plankton communities from tropical to polar ecosystems. Communities can be split into three extreme typologies: diatom/copepod-dominated in eutrophic blooms, rhizarian/chaetognath-dominated in oligotrophic tropical oceans, and gelatinous-dominated elsewhere. While plankton taxonomic composition changes with latitude, functional and trophic structures mostly depend on the amount of prey available for each trophic level. Given future projections of oligotrophication of marine ecosystems, our findings suggest that rhizarian and gelatinous organisms will increasingly dominate the apex position of planktonic ecosystems, leading to significant changes in the ocean’s carbon cycle.

Plankton size spectra are important indicators of the ecosystem state, yet such measurements are typically biased by the available sampling methods. Here, we combined individual size measurement from two zooplankton imaging approaches—in situ observation by the Underwater Vision Profiler5 and Multinet-collection supplemented by ex situ imaging via Zooscan—obtained in the global ocean, to calculate zooplankton normalized biovolume size spectra (NBSS) for all organisms larger than 1 mm. The reconstructed NBSS combining both datasets resulted in increased biomass estimates by adding organisms poorly sampled by either of the methods. The optimal values measured by both methods are used to reconstruct the zooplankton biovolume and biomass distributions. The reconstructed slopes appeared steeper and closer to those measured only by the UVP5 (+7.6%) and flatter than those obtained only from the Multinet (−20%), particularly in tropical and temperate latitudes. The main difference in tropical and temperate NBSS from the two devices is due to the fragile rhizarians that were not accounted for when using net data. When possible, we suggest using in situ and ex situ technologies together, and we provide potential indications on how to correct for missing components of the community when only one method is available.

Coral reefs are marine biodiversity hotspots that provide a wide range of ecosystem services. They are also reservoirs of bioactive compounds, many of which are produced by microbial symbionts associated with reef invertebrate hosts. However, for the keystone species of coral reefs, the reef-building corals themselves, we still lack a systematic assessment of their microbially encoded biosynthetic potential, and thus the molecular resources that may be at stake due to the alarming decline in reef biodiversity and cover. Here, we analysed microbial genomes reconstructed from 820 reef-building coral samples of three representative coral genera collected at 99 reefs across 32 islands during a two-year expedition throughout the Pacific Ocean (Tara Pacific). By contextualising our analyses with the microbiomes of other reef species, we found that genomic information was previously available for only 10% of the 4,224 microbial species overall and for less than 1% of the 645 species exclusively identified in Tara Pacific samples. We found reef-building coral microbiomes to be host-specific and their biosynthetic potential to rival or even surpass that found in traditional targets for natural product discovery, such as sponges and soft corals. Fire corals were not only particularly diverse in microbially encoded biosynthetic gene clusters (BGCs), but also in BGC-rich bacteria, including Acidobacteriota spp., which have been recently highlighted for their promising natural product repertoire. Together, this study unveils new candidate sources for bioactive compound discovery, prioritises targets for microbial isolation, and underscores the importance of conservation efforts by linking macro-organismal biodiversity loss to host-specific microbiomes and their biotechnological potential.

Plankton ecologists have long used the Normalized Biomass Size Spectrum (NBSS) as a common framework to study the size distribution of aquatic bacteria, phytoplankton, and zooplankton across various temporal and spatial scales. Systematic NBSS measurements have shown that its shape varies across ecosystems and could be used as an indicator of the state of the ecosystem. Indeed, NBSS slopes typically indicate how efficiently biomass is transferred across sizes, impacting the throughput of the biological carbon pump. Zooplankton, in particular, influences the carbon pump by feeding on and repackaging phytoplankton production, as well as respiring O2 at rates that may exceed its replenishment, contributing to the existence of Oxygen Minimum Zones (OMZ) located in the Pacific, Indian, and Atlantic Oceans. Using a range of non-intrusive imaging devices, which produce community composition datasets along with complementary size measurements of individual organisms, we investigate the size distribution of zooplankton in the Atlantic Ocean. As part of our ongoing efforts to create a Pelagic Size Structure database (PSSdb, https://www.st.nmfs.noaa.gov/copepod/pssdb/), we will present a regional assessment of zooplankton NBSSs computed at different scales and compare them to estimates generated at the global scale. We will also investigate the response of zooplankton to environmental factors, including low concentrations of dissolved O2, to foresee how the gatekeepers of the marine biological carbon pump may be impacted by future anthropogenic pressures.

Coral reefs are severely threatened by global and local environmental changes. However, susceptibility to perturbations and subsequent mortality varies among coral species. In this study, we tested the contribution of genetic and environmental conditions to coral's phenotypic response in Pocillopora spp. and Porites spp. sampled together at a large ecological and temporal scale throughout the Pacific Ocean. We assessed coral phenotype signatures using a multi-biomarker approach (animal and symbiont biomasses, protein carbonylation and ubiquitination and total antioxidant capacities). In both genera, we highlighted a strong anticorrelation between the redox state and the animal and symbiont biomasses. In addition, Pocillopora exhibited high phenotypic plasticity, responding to various environmental variables such as temperature, nutrients, phosphate, and carbonate chemistry. In contrast, Porites displayed more robust phenotypes influenced by both genetics and past climate events. In conclusion, co-located coral species display different phenotypic response strategies that are influenced by different environmental conditions.

Plastic debris is a ubiquitous pollutant found from the sea surface to the seafloor. Understanding the mechanisms driving its pollution is a difficult task mostly due to the complex oceanic circulation, which affects plastic debris in manifold ways. The Lagrangian approach is hence a natural framework to study this problem. Here, I will show the results of TrackMPD, a Lagrangian model simulating the pathways of plastic debris in the Mediterranean Sea, and validated with the most extensive dataset of plastic measurements in this region to date. The Mediterranean Sea lacks in zones of plastic accumulation despite being one of the most polluted basins worldwide. Here, we adopt a different paradigm, by identifying crossroad regions through which large amounts of plastic debris flow. We find that around 20% of Mediterranean plastic debris passed through 1% of the basin surface. The most important crossroads intercepted plastic debris from multiple sources, which had often traveled long distances. During its travel, plastic debris can be colonised by marine organisms, and eventually sink. We found that the locations where debris leaves the surface are significantly different from those where it reaches the seafloor: debris travels hundreds of kilometers during its sinking. In the water column, plastic debris can potentially be mistaken for zooplankton and be ingested, thus impacting marine biota. To quantify this risk, we estimated the plastic debris to zooplankton ratio over the entire Mediterranean Sea, showing a high risk of contamination for both pelagic fish and whales.

Aquatic ecologists face challenges in identifying the general rules of the functioning of ecosystems. A common framework, including freshwater, marine, benthic, and pelagic ecologists, is needed to bridge communication gaps and foster knowledge sharing. This framework should transcend local specificities and taxonomy in order to provide a common ground and shareable tools to address common scientific challenges. In a recent review paper published in Limnology and Oceanography (Martini et al., 2021), we advocated the use of functional trait-based approaches (FTBAs) for aquatic ecologists and proposed concrete paths to go forward. In this presentation, we will first present an overview of this synthesis work. Then, using a few examples of recent results, including from quantitative imaging, genomics, and machine learning, we will then concretely illustrate how FTBAs can allow aquatic ecologists to tackle some of the scientific challenges identified in the paper.

Health and resilience of the coral holobiont depend on diverse bacterial communities often dominated by key marine symbionts of the Endozoicomonadaceae family. The factors controlling their distribution and their functional diversity remain, however, poorly known. Here, we study the ecology of Endozoicomonadaceae at an ocean basin-scale by sampling specimens from three coral genera ( Pocillopora , Porites , Millepora ) on 99 reefs from 32 islands across the Pacific Ocean. The analysis of 2447 metabarcoding and 270 metagenomic samples reveals that each coral genus harbored a distinct new species of Endozoicomonadaceae . These species are composed of nine lineages that have distinct biogeographic patterns. The most common one, found in Pocillopora , appears to be a globally distributed symbiont with distinct metabolic capabilities, including the synthesis of amino acids and vitamins not produced by the host. The other lineages are structured partly by the host genetic lineage in Pocillopora and mainly by the geographic location in Porites . Millepora is more rarely associated to Endozoicomonadaceae . Our results show that different coral genera exhibit distinct strategies of host- Endozoicomonadaceae associations that are defined at the bacteria lineage level.

The objective of the TONGA oceanographic expedition was to study the control of productivity and carbon sequestration by micronutrients of shallow hydrothermal origin in the Western Tropical South Pacific (WTSP) Ocean. The 37-day oceanographic survey took place on board the R/V L’Atalante in 2019 between Oct. 31 to Dec. 6 (Nouméa-Nouméa). Over a large area of the WTSP the team acquired numerous results on both the entire water column (up to the sediment) and the atmosphere. Specific task are represented on figure 1: (task 1) to characterize chemically and optically shallow hydrothermal fluids and to compare the source from below (shallow hydrothermal fluids) with the source from above (atmospheric deposition); (task 2) to quantify the dynamical dispersion of the fluids at small and regional scale; (task 3) to investigate the impact of the shallow hydrothermal sources on the biological activity and diversity, and the feedback to the atmosphere via the oceanic emissions of primary and secondary aerosols. (Task 4) to communicate about the campaign (see for example our Tweeter account (https://twitter.com/tongaproject) and the movie (26’) both in French (https://www.youtube.com/watch?v=e5kAd0i6Dck) and English (https://www.youtube.com/watch?v=UeABf-cVR-k). A long west to east (up to the blue waters of the gyre) transect allowed to characterize the different biogeochemical provinces crossed and a focus in the region of the Lau Basin allowed to investigate the impact of shallow hydrothermal sources. A series of short and long stations allowed to fully characterize the stocks and the fluxes in the different provinces. Short-term (up to 10 days) processes studies have been conducted (drifting moorings and minicosms experiments). Part of these results will feed into important modeling work. A fixed mooring line launched at the end of the campaign and recovered in Nov. 2020 as well as the 7 ARGO floats and 20 drifting buoys that were dropped during the campaign provide a broader temporal context of the acquisitions done during the campaign. An important focus of the campaign was the trace metal characterization of the entire water column. For this, TONGA has been labeled by the international program GEOTRACES (https://www.geotraces.org/). The impact on biological communities of fluids is supported by the international IMBER program (https://imber.info/). The TONGA project is also part of the LEFE program (funding by LEFE-CYBER and LEFE-GMMC), the ANR (Appel à projets génériques) and the Fondation A-MIDeX of the Aix-Marseille Université.

Coral reefs are considered one of the most emblematic ecosystems in our oceans, but their existence is increasingly threatened by climate change. In this study, natural populations of two reef-building coral genera, Pocillopora spp. and Porites spp., and one hydrocoral Millepora cf. platyphylla from two different marine provinces in the Pacific Ocean were investigated using a multi-omics approach as part of the Tara Pacific expedition. Here, we propose a standardised method consisting of a biphasic extraction method followed by metabolomics analysis using mass spectrometry for the lipidome and 1 H nuclear magnetic resonance for hydrophilic metabolites. Our study assessed a broad range of the metabolome and is the first to identify and add 24 compounds by NMR and over 200 lipids by MS analyses for corals. Metabolic profiles were distinct among genera but not within genotypes of the cnidarian corals. Although endosymbiotic dinoflagellates of the family Symbiodiniaceae are known to play a central role in the metabolomic signature of the coral holobiont, they did not account for all differences. This suggests that a combined effect by different members of the coral holobiont and an interaction with the environment might be at play. Our study provides foundational knowledge on the coral holobiont metabolome.

The Western Tropical South Pacific (WTSP) basin has been identified as a hotspot of atmospheric dinitrogen fixation due to the high dissolved iron ([DFe]) concentrations (up to 66 nM) in the photic layer linked with the release of shallow hydrothermal fluids along the Tonga-Kermadec arc. Yet, the effect of such hydrothermal fluids in structuring the plankton community remains poorly studied. During the TONGA cruise (November-December 2019), we collected micro- (20-200 μm) and meso-plankton (>200 μm) samples in the photic layer (0-200 m) along a west to east zonal transect crossing the Tonga volcanic arc, in particular two volcanoes associated with shallow hydrothermal vents (< 500 m) in the Lau Basin, and both sides of the arc represented by Melanesian waters and the South Pacific Gyre. Samples were analyzed by quantitative imaging (FlowCam and ZooScan) and then coupled with acoustic observations, allowing us to study the potential transfer of phytoplankton blooms to higher planktonic trophic levels. We show that micro- and meso-plankton exhibit high abundances and biomasses in the Lau Basin and, to some extent, in Melanesian waters, suggesting that shallow hydrothermal inputs sustain the planktonic food web, creating productive waters in this otherwise oligotrophic region. In terms of planktonic community structure, we identified major changes with high [DFe] inputs, promoting the development of a low diversity planktonic community dominated by diazotrophic cyanobacteria. Furthermore, in order to quantify the effect of the shallow hydrothermal vents on chlorophyll a concentrations, we used Lagrangian dispersal models. We show that chlorophyll a concentrations were significantly higher inside the Lagrangian plume, which came into contact with the two hydrothermal sites, confirming the profound impact of shallow hydrothermal vents on plankton production.

The Underwater Vision Profiler (UVP) has been developed to study the number, size and shape of particles (size \textgreater 80µm) and plankton (size \textgreater 700µm) in situ. Over the last decade, thousands of profiles have been collected in the world's oceans by the UVP5 to better understand and quantify processes affecting community compositions of large plankton and the biological carbon pump. These data, used together with modeling approaches helped estimate plankton global carbon biomass and particle vertical flux. The most recent UVP (UVP6) sensors have been developed to be mounted on autonomous platforms, mooring and CTD rosettes down to 6000 m depth. Fully inter-calibrated, they record particles and identify plankton and marine snow after recovery or during deployment using an embedded recognition algorithm. A complete software ecosystem is used to pilot the instrument, record the data, and make them available to fulfill the global need of easy data access expressed by scientists, policy makers and the public. Because of the cost reduction of the UVP6, its capability to be mounted on many platforms including autonomous ones, the Ocean is being quickly populated by this sensor (125 sensors have been in operation in the last 2 years). Recent plankton community composition, particle mass, and flux data from three different basins in the Atlantic will be presented. In the next decade, the massive global monitoring of these key biological Essential Oceanographic Variables will significantly advance our understanding of key aquatic processes including the biological carbon pump.

Les données issues des comptages de zooplancton gélatineux effectués lors des campagnes halieutiques sont des données quantitatives mais non standardisées (i.e. non comparables d’une campagne à l’autre, ou d’un trait à l’autre). Cette note technique explore les questionnements méthodologiques permettant la standardisation et la comparaison de ces données et présente une proposition de méthode d’estimation de l’abondance du zooplancton gélatineux à partir de captures par chalutage. Ce travail fait suite aux réflexions antérieures menées dans le cadre de la DCSMM par Sandrine Vaz, Fabien Morandeau, Fabien Lombard et Jacques Sacchi concernant l’exploitation des données de zooplancton gélatineux acquises par chalutage (Aubert et al. 2018 ; Lheureux et al. 2022). Ces travaux ont été poursuivis dans le cadre du projet R&D GELATINE et les principales propositions et résultats sont discutés ici au regard des données existantes (types de chaluts, distance de chalutage et référentiel utilisé, zone filtrante du chalut).

Heat waves are causing declines in coral reefs globally. Coral thermal responses depend on multiple, interacting drivers, such as past thermal exposure, endosymbiont community composition, and host genotype. This makes the understanding of their relative roles in adaptive and/or plastic responses crucial for anticipating impacts of future warming. Here, we extracted DNA and RNA from 102 $Pocillopora$ colonies collected from 32 sites on 11 islands across the Pacific Ocean to characterize host-photosymbiont fidelity and to investigate patterns of gene expression across a historical thermal gradient. We report high host-photosymbiont fidelity and show that coral and microalgal gene expression respond to different drivers. Differences in photosymbiotic association had only weak impacts on host gene expression, which was more strongly correlated with the historical thermal environment, whereas, photosymbiont gene expression was largely determined by microalgal lineage. Overall, our results reveal a three-tiered strategy of thermal acclimatization in $Pocillopora$ underpinned by host-photosymbiont specificity, host transcriptomic plasticity, and differential photosymbiotic association under extreme warming.

Background: Over the last decade, several coral genomes have been sequenced allowing a better understanding of these symbiotic organisms threatened by climate change. Scleractinian corals are reef builders and are central to coral reef ecosystems, providing habitat to a great diversity of species. Results: In the frame of the Tara Pacific expedition, we assemble two coral genomes, Porites lobata and Pocillopora cf. effusa, with vastly improved contiguity that allows us to study the functional organization of these genomes. We annotate their gene catalog and report a relatively higher gene number than that found in other public coral genome sequences, 43,000 and 32,000 genes, respectively. This finding is explained by a high number of tandemly duplicated genes, accounting for almost a third of the predicted genes. We show that these duplicated genes originate from multiple and distinct duplication events throughout the coral lineage. They contribute to the amplification of gene families, mostly related to the immune system and disease resistance, which we suggest to be functionally linked to coral host resilience. Conclusions: At large, we show the importance of duplicated genes to inform the biology of reef-building corals and provide novel avenues to understand and screen for differences in stress resilience. † Benjamin Noel and France Denoeud have equal contribution.

Telomeres are environment-sensitive regulators of health and aging. Here,we present telomere DNA length analysis of two reef-building coral genera revealing that the long- and short-term water thermal regime is a key driver of between-colony variation across the Pacific Ocean. Notably, there are differences between the two studied genera. The telomere DNA lengths of the short-lived, more stress-sensitive Pocillopora spp. colonies were largely determined by seasonal temperature variation, whereas those of the long-lived, more stress-resistant Porites spp. colonies were insensitive to seasonal patterns, but rather influenced by past thermal anomalies. These results reveal marked differences in telomere DNA length regulation between two evolutionary distant coral genera exhibiting specific life-history traits. We propose that environmentally regulated mechanisms of telomere maintenance are linked to organismal performances, a matter of paramount importance considering the effects of climate change on health.

Tropical coral reefs are among the most affected ecosystems by climate change and face increasing loss in the coming decades. Effective conservation strategies that maximize ecosystem resilience must be informed by the accurate characterization of extant genetic diversity and population structure together with an understanding of the adaptive potential of keystone species. Here we analyzed samples from the Tara Pacific Expedition (2016-2018) that completed an 18,000 km longitudinal transect of the Pacific Ocean sampling three widespread corals-Pocillopora meandrina, Porites lobata, and Millepora cf. platyphylla-across 33 sites from 11 islands. Using deep metagenomic sequencing of 269 colonies in conjunction with morphological analyses and climate variability data, we can show that despite a targeted sampling the transect encompasses multiple cryptic species. These species exhibit disparate biogeographic patterns and, most importantly, distinct evolutionary patterns in identical environmental regimes. Our findings demonstrate on a basin scale that evolutionary trajectories are species-specific and can only in part be predicted from the environment. This highlights that conservation strategies must integrate multi-species investigations to discern the distinct genomic footprints shaped by selection as well as the genetic potential for adaptive change.

Plankton size spectra are important indicators of the ecosystem state, as they illustrate the quantity of organisms available for higher marine food web and reflect multiple size-dependent processes. Yet, such measurements are typically biased by the available sampling methods, either disrupting fragile organisms or lacking good resolution (in size and/or time and space). In this study, we combined two of the most common approaches to measure zooplankton Normalized Biomass/Biovolume Size Spectra (NBSS) to calculate a complete zooplankton distribution for organisms larger than 1 mm. The reconstructed NBSS slopes appeared steeper and closer to those measured by the UVP5 (+7.6%) and flatter than those of the Multinet (- 20%) particularly in tropics and temperate latitudes. The overall gain in polar biomass was relatively small for reconstructed biomass compared to bulk estimates from Multinet (+0.24 mgC/m3 or +4.25%) and high from the UVP5 (+2.0 mgC/m3 or +53%). In contrast, in the tropical and temperate ecosystems, the gain in biomass was small for UVP5 (+0.67 mgC/m3 or +30.44% and +0.74 mgC/m3 or +19.59% respectively) and high for Multinet (+1.66 mgC/m3 or +136% and +3.4 mgC/m3 or +309% respectively). Given these differences, we suggest here to combine in situ imaging sensors and net data in any comprehensive study exploring key living players in the ocean ecosystem and their contributions to the biological pump.

Aim The distribution of mesoplankton communities have been poorly studied at global scale, especially from in situ instruments. This study aims to (1) describe the global distribution of mesoplankton communities in relation with their environment and (2) assess the ability of various environmental-based ocean regionalisations to explain the distribution of these communities. Location Global ocean, 0-500 m depth. Time period 2008 - 2019 Major taxa studied 28 groups of large mesoplanktonic and macroplanktonic organ- isms, covering Metazoa, Rhizaria and Cyanobacteria. Methods From a global data set of 2500 vertical profiles making use of the Underwater Vision Profiler 5 (UVP5), an in situ imaging instrument, we studied the global distribu- tion of large (> 600 μm) mesoplanktonic organisms. Among the 6.8 million imaged ob- jects, 330,000 were large zooplanktonic organisms and phytoplankton colonies, the rest consisting of marine snow particles. Multivariate ordination (PCA) and clustering were used to describe patterns in community composition, while comparison with existing regionalisations was performed with regression methods (RDA). Results Within the observed size range, epipelagic plankton communities were Trichodesmium-enriched in the intertropical Atlantic, Copepoda-enriched at high latitudes and in upwelling areas, and Rhizaria-enriched in oligotrophic areas. In the mesopelagic layer, Copepoda-enriched communities were also found at high latitudes and in the At- lantic Ocean, while Rhizaria-enriched communities prevailed in the Peruvian upwelling system and a few mixed communities were found elsewhere. The comparison between the distribution of these communities and a set of existing regionalisations of the ocean suggested that the structure of plankton communities described above is mostly driven by basin-level environmental conditions. Main conclusions n both layers, three types of plankton communities emerged and seemed to be mostly driven by regional environmental conditions. This work sheds light on the role not only of metazoans, but also of unexpected large protists and cyanobacteria in structuring large mesoplankton communities.

Coral reefs are among the most diverse ecosystems on Earth. They support high biodiversity of multicellular organisms that strongly rely on associated microorganisms for health and nutrition. However, the extent of the coral reef microbiome diversity and its distribution at the oceanic basin-scale remains to be explored. Here, we systematically sampled 3 coral morphotypes, 2 fish species, and planktonic communities in 99 reefs from 32 islands across the Pacific Ocean, to assess reef microbiome composition and biogeography. We show a very large richness of reef microorganisms compared to other environments, which extrapolated to all fishes and corals of the Pacific, approximates the current estimated total prokaryotic diversity for the entire Earth. Microbial communities vary among and within the 3 animal biomes (coral, fish, plankton), and geographically. For corals, the cross-ocean patterns of diversity are different from those known for other multicellular organisms. Within each coral morphotype, community composition is always determined by geographic distance first, both at the island and across ocean scale, and then by environment. Our unprecedented sampling effort of coral reef microbiomes, as part of the Tara Pacific expedition, provides new insight into the global microbial diversity, the factors driving their distribution, and the biocomplexity of reef ecosystems.

Zooplankton are major consumers of phytoplankton primary production in marine ecosystems. As such, they represent a critical link for energy and matter transfer between phytoplankton and bacterioplankton to higher trophic levels and play an important role in global biogeochemical cycles. In this Review, we discuss key responses of zooplankton to ocean warming, including shifts in phenology, range, and body size, and assess the implications to the biological carbon pump and interactions with higher trophic levels. Our synthesis highlights key knowledge gaps and geographic gaps in monitoring coverage that need to be urgently addressed. We also discuss an integrated sampling approach that combines traditional and novel techniques to improve zooplankton observation for the benefit of monitoring zooplankton populations and modelling future scenarios under global changes.

Abstract Endogenous viral elements (EVEs) offer insight into the evolutionary histories and hosts of contemporary viruses. This study leveraged DNA metagenomics and genomics to detect and infer the host of a non-retroviral dinoflagellate-infecting +ssRNA virus (dinoRNAV) common in coral reefs. As part of the Tara Pacific Expedition, this study surveyed 269 newly sequenced cnidarians and their resident symbiotic dinoflagellates (Symbiodiniaceae), associated metabarcodes, and publicly available metagenomes, revealing 178 dinoRNAV EVEs, predominantly among hydrocoral-dinoflagellate metagenomes. Putative associations between Symbiodiniaceae and dinoRNAV EVEs were corroborated by the characterization of dinoRNAV-like sequences in 17 of 18 scaffold-scale and one chromosome-scale dinoflagellate genome assembly, flanked by characteristically cellular sequences and in proximity to retroelements, suggesting potential mechanisms of integration. EVEs were not detected in dinoflagellate-free (aposymbiotic) cnidarian genome assemblies, including stony corals, hydrocorals, jellyfish, or seawater. The pervasive nature of dinoRNAV EVEs within dinoflagellate genomes (especially Symbiodinium ), as well as their inconsistent within-genome distribution and fragmented nature, suggest ancestral or recurrent integration of this virus with variable conservation. Broadly, these findings illustrate how +ssRNA viruses may obscure their genomes as members of nested symbioses, with implications for host evolution, exaptation, and immunity in the context of reef health and disease.

The Arctic Ocean (AO) is being rapidly transformed by global warming, but its biodiversity remains understudied for many planktonic organisms, in particular for unicellular eukaryotes that play pivotal roles in marine food webs and biogeochemical cycles. The aim of this study was to characterize the biogeographic ranges of species that comprise the contemporary pool of unicellular eukaryotes in the AO as a first step toward understanding mechanisms that structure these communities and identifying potential target species for monitoring. Leveraging the Tara Oceans DNA metabarcoding data, we mapped the global distributions of operational taxonomic units (OTUs) found on Arctic shelves into five biogeographic categories, identified biogeographic indicators, and inferred the degree to which AO communities of unicellular eukaryotes share members with assemblages from lower latitudes. Arctic/Polar indicator OTUs, as well as some globally ubiquitous OTUs, dominated the detection and abundance of DNA reads in the Arctic samples. OTUs detected only in Arctic samples (Arctic-exclusives) showed restricted distribution with relatively low abundances, accounting for 10–16% of the total Arctic OTU pool. OTUs with high abundances in tropical and/or temperate latitudes (non-Polar indicators) were also found in the AO but mainly at its periphery. We observed a large change in community taxonomic composition across the Atlantic-Arctic continuum, supporting the idea that advection and environmental filtering are important processes that shape plankton assemblages in the AO. Altogether, this study highlights the connectivity between the AO and other oceans, and provides a framework for monitoring and assessing future changes in this vulnerable ecosystem.

Abstract Coral reef science is a fast-growing field propelled by the need to better understand coral health and resilience to devise strategies to slow reef loss resulting from environmental stresses. Key to coral resilience are the symbiotic interactions established within a complex holobiont, i.e . the multipartite assemblages comprising the coral host organism, endosymbiotic dinoflagellates, bacteria, archaea, fungi, and viruses. Tara Pacific is an ambitious project built upon the experience of previous Tara Oceans expeditions, and leveraging state-of-the-art sequencing technologies and analyses to dissect the biodiversity and biocomplexity of the coral holobiont screened across most archipelagos spread throughout the entire Pacific Ocean. Here we detail the Tara Pacific workflow for multi-omics data generation, from sample handling to nucleotide sequence data generation and deposition. This unique multidimensional framework also includes a large amount of concomitant metadata collected side-by-side that provide new assessments of coral reef biodiversity including micro-biodiversity and shape future investigations of coral reef dynamics and their fate in the Anthropocene.

ABSTRACT: Appendicularians are abundant planktonic filter feeders that play a significant role in the pelagic food web due to their high clearance rates. Their diet and feeding rates have typically been measured as bulk chlorophyll or cell removal, with some attention given to prey size but no differentiation between the microbial phylotypes. Using a combination of \textitin situ and laboratory incubations with flow cytometry and next-generation sequencing, we found species-specific differences in clearance rates and diet compositions of 4 common species: \textitOikopleura albicans, \textitO. fusiformis, \textitO. longicauda, and \textitO. dioica. While \textitO. albicans most efficiently removed nano-eukaryotic algae, the other smaller species preferentially removed micron-sized pico-eukaryotic algae. Pico- and nano-eukaryotic cells constituted the major food source of the studied appendicularians despite their occurrence in oligotrophic water dominated by prokaryotic cells. Across species, pico- and nano-planktonic microalgae biomass comprised 45 to 75% of the appendicularian diets. Although non-photosynthetic bacteria were removed at lower rates than all other prey groups, their total contribution to the appendicularian diet was not trivial, representing 5 to 19% of the planktonic carbon in the appendicularian diet; pico-cyanobacteria contributed an additional 9 to 18%. Removal rates and efficiencies of pico-eukaryotes were higher than those of prokaryotes of similar size. Strikingly different clearance rates were observed for different prokaryotic phylotypes, indicating that factors other than size are involved in determining the capturability of the cells. Collectively, our findings provide additional evidence for differential retention of microbial prey among mucous-mesh grazers and its substantial effect on the upper-ocean microbial community.

Floating plastic debris is a pervasive pollutant in seas and oceans, affecting a wide range of animals. In particular, microplastics (<5 mm in size) increase the possibility that marine species consume plastic and enter the food chain. The present study investigates this potential mistake between plastic debris and zooplankton by calculating the plastic debris to zooplankton ratio over the whole Mediterranean Sea. To this aim, in situ data from the Tara Mediterranean Expedition are combined with environmental and Lagrangian diagnostics in a machine learning approach to produce spatially-explicit maps of plastic debris and zooplankton abundance. We then analyse the plastic to zooplankton ratio in regions with high abundances of pelagic fish. Two of the major hotspots of pelagic fish, located in the Gulf of Gabes and Cilician basin, were associated with high ratio values. Finally, we compare the plastic to zooplankton ratio values in the Pelagos Sanctuary, an important hotspot for marine mammals, with other Geographical Sub-Areas, and find that they were among the larger of the Western Mediterranean Sea. Our results indicate a high potential risk of contamina-tion of marine fauna by plastic and advocate for novel integrated modelling approaches which account for potential trophic transfer within the food chain.

For decades, marine plankton have been investigated for their capacity to modulate biogeochemical cycles and provide fishery resources. Between the sunlit (epipelagic) layer and the deep dark waters, lies a vast and heterogeneous part of the ocean: the mesopelagic zone. How plankton composition is shaped by environment has been well-explored in the epipelagic but much less in the mesopelagic ocean. Here, we conducted comparative analyses of trans-kingdom community assemblages thriving in the mesopelagic oxygen minimum zone (OMZ), mesopelagic oxic, and their epipelagic counterparts. We identified nine distinct types of intermediate water masses that correlate with variation in mesopelagic community composition. Furthermore, oxygen, NO 3 − and particle flux together appeared as the main drivers governing these communities. Novel taxonomic signatures emerged from OMZ while a global co-occurrence network analysis showed that about 70% of the abundance of mesopelagic plankton groups is organized into three community modules. One module gathers prokaryotes, pico-eukaryotes and Nucleo-Cytoplasmic Large DNA Viruses (NCLDV) from oxic regions, and the two other modules are enriched in OMZ prokaryotes and OMZ pico-eukaryotes, respectively. We hypothesize that OMZ conditions led to a diversification of ecological niches, and thus communities, due to selective pressure from limited resources. Our study further clarifies the interplay between environmental factors in the mesopelagic oxic and OMZ, and the compositional features of communities.

With climate projections questioning the future survival of stony corals and their dominance as tropical reef builders, it is critical to understand the adaptive capacity of corals to ongoing climate change. Biological mediation of the carbonate chemistry of the coral calcifying fluid is a fundamental component for assessing the response of corals to global threats. The Tara Pacific expedition (2016–2018) provided an opportunity to investigate calcification patterns in extant corals throughout the Pacific Ocean. Cores from colonies of the massive Porites and Diploastrea genera were collected from different environments to assess calcification parameters of long-lived reef-building corals. At the basin scale of the Pacific Ocean, we show that both genera systematically up-regulate their calcifying fluid pH and dissolved inorganic carbon to achieve efficient skeletal precipitation. However, while Porites corals increase the aragonite saturation state of the calcifying fluid (Ωcf) at higher temperatures to enhance their calcification capacity, Diploastrea show a steady homeostatic Ωcf across the Pacific temperature gradient. Thus, the extent to which Diploastrea responds to ocean warming and/or acidification is unclear, and it deserves further attention whether this is beneficial or detrimental to future survival of this coral genus.

the Tara Pacific expedition (2016-2018) sampled coral ecosystems around 32 islands in the Pacific Ocean and the ocean surface waters at 249 locations, resulting in the collection of nearly 58 000 samples. The expedition was designed to systematically study warm-water coral reefs and included the collection of corals, fish, plankton, and seawater samples for advanced biogeochemical, molecular, and imaging analysis. Here we provide a complete description of the sampling methodology, and we explain how to explore and access the different datasets generated by the expedition. Environmental context data were obtained from taxonomic registries, gazetteers, almanacs, climatologies, operational biogeochemical models, and satellite observations. The quality of the different environmental measures has been validated not only by various quality control steps, but also through a global analysis allowing the comparison with known environmental large-scale structures. Such publicly released datasets open the perspective to address a wide range of scientific questions.

The Tara Microplastics mission was conducted for 7 months to investigate plastic pollution along nine major rivers in Europe-Thames, Elbe, Rhine, Seine, Loire, Garonne, Ebro, Rhone, and Tiber. An extensive suite of sampling protocols was applied at four to five sites on each river along a salinity gradient from the sea and the outer estuary to downstream and upstream of the first heavily populated city. Biophysicochemical parameters including salinity, temperature, irradiance, particulate matter, large and small microplastics (MPs) concentration and composition, prokaryote and microeukaryote richness, and diversity on MPs and in the surrounding waters were routinely measured onboard the French research vessel Tara or from a semi-rigid boat in shallow waters. In addition, macroplastic and microplastic concentrations and composition were determined on river banks and beaches. Finally, cages containing either pristine pieces of plastics in the form of films or granules, and others containing mussels were immersed at each sampling site, 1 month prior to sampling in order to study the metabolic activity of the plastisphere by meta-OMICS and to run toxicity tests and pollutants analyses. Here, we fully described the holistic set of protocols designed for the Mission Tara Microplastics and promoted standard procedures to achieve its ambitious goals: (1) compare traits of plastic pollution among European rivers, (2) provide a baseline of the state of plastic pollution in the Anthropocene, (3) predict their evolution in the frame of the current European initiatives, (4) shed light on the toxicological effects of plastic on aquatic life, (5) model the transport of microplastics from land towards the sea, and (6) investigate the potential impact of pathogen or invasive species rafting on drifting plastics from the land to the sea through riverine systems.

Autonomous and cabled platforms are revolutionizing our understanding of ocean systems by providing 4D monitoring of the water column, thus going beyond the reach of ship-based surveys and increasing the depth of remotely sensed observations. However, very few commercially available sensors for such platforms are capable of monitoring large particulate matter (100-2000 μm) and plankton despite their important roles in the biological carbon pump and as trophic links from phytoplankton to fish. Here, we provide details of a new, commercially available scientific camera-based particle counter, specifically designed to be deployed on autonomous and cabled platforms: the Underwater Vision Profiler 6 (UVP6). Indeed, the UVP6 camera-and-lighting and processing system, while small in size and requiring low power, provides data of quality comparable to that of previous much larger UVPs deployed from ships. We detail the UVP6 camera settings, its performance when acquiring data on aquatic particles and plankton, their quality control, analysis of its recordings, and streaming from in situ acquisition to users. In addition, we explain how the UVP6 has already been integrated into platforms such as BGC-Argo floats, gliders and long-term mooring systems (autonomous platforms). Finally, we use results from actual deployments to illustrate how UVP6 data can contribute to addressing longstanding questions in marine science, and also suggest new avenues that can be explored using UVP6-equipped autonomous platforms.

For more than a decade, high-throughput sequencing has transformed the study of marine planktonic communities and has highlighted the extent of protist diversity in these ecosystems. Nevertheless, little is known relative to their genomic diversity at the species-scale as well as their major speciation mechanisms. An increasing number of data obtained from global scale sampling campaigns is becoming publicly available, and we postulate that metagenomic data could contribute to deciphering the processes shaping protist genomic differentiation in the marine realm. As a proof of concept, we developed a findable, accessible, interoperable and reusable (FAIR) pipeline and focused on the Mediterranean Sea to study three a priori abundant protist species: Bathycoccus prasinos, Pelagomonas calceolata and Phaeocystis cordata. We compared the genomic differentiation of each species in light of geographic, environmental and oceanographic distances. We highlighted that isolation-byenvironment shapes the genomic differentiation of B. prasinos, whereas P. cordata is impacted by geographic distance (i.e. isolation-by-distance). At present time, the use of metagenomics to accurately estimate the genomic differentiation of protists remains challenging since coverages are lower compared to traditional population surveys. However, our approach sheds light on ecological and evolutionary processes occurring within natural marine populations and paves the way for future protist population metagenomic studies.

Plankton imaging systems supported by automated classification and analysis have improved ecologists' ability to observe aquatic ecosystems. Today, we are on the cusp of reliably tracking plankton populations with a suite of lab-based and in situ tools, collecting imaging data at unprecedentedly fine spatial and temporal scales. But these data streams have potential well beyond examining the abundances of different taxa; the individual images themselves contain a wealth of information on functional traits. Here we outline traits that could be measured from image data, suggest computer vision approaches to extract functional trait information from the images, and discuss promising avenues for novel studies. The approaches we discuss are data agnostic and are broadly applicable to other aquatic or terrestrial organisms.

World ocean plankton quantitative biodiversity data are still severely limited due to the high cost and logistical constraints associated to oceanographic vessels and collection/analytic devices. Here, we report the first use of an affordable and open-source plankton collection and imaging kit designed for citizen biological oceanography, composed of a high-speed surface plankton net, the Coryphaena , together with a portable in-flux automated imaging device, the PlanktoScope . We deployed this kit in December 2020 along a latitudinal transect across the Atlantic Ocean on board the schooner Tara , during the first Leg of her ‘Mission Microbiomes’. The citizen-science instruments were benchmarked and compared at sea to state-of-the-art protocols applied in previous Tara expeditions, i.e. on-board water pumping and filtration system and the FlowCam to respectively sample and image total micro-plankton. Results show that the Coryphaena can collect pristine micro-plankton at speed up to 11 knots, generating quantitative imaging data comparable to those obtained from total, on-board filtered water, and that the PlanktoScope and FlowCam provide comparable data. Overall, the new citizen tools provided a complete picture of surface micro-plankton composition, biogeography and biogeochemistry, opening the way toward a global, cooperative, and frugal plankton observatory network at planetary scale.

Remote deep-ocean sediment (DOS) ecosystems are among the least explored biomes on Earth. Genomic assessments of their biodiversity have failed to separate indigenous benthic organisms from sinking plankton. Here, we compare global-scale eukaryotic DNA metabarcoding datasets (18 S -V9) from abyssal and lower bathyal surficial sediments and euphotic and aphotic ocean pelagic layers to distinguish plankton from benthic diversity in sediment material. Based on 1685 samples collected throughout the world ocean, we show that DOS diversity is at least threefold that in pelagic realms, with nearly two-thirds represented by abundant yet unknown eukaryotes. These benthic communities are spatially structured by ocean basins and particulate organic carbon (POC) flux from the upper ocean. Plankton DNA reaching the DOS originates from abundant species, with maximal deposition at high latitudes. Its seafloor DNA signature predicts variations in POC export from the surface and reveals previously overlooked taxa that may drive the biological carbon pump.

Over the last decade, plankton research has experienced extensive developments in automatic image acquisition for identifying and quantifying plankton species. This information is useful for the reporting of plankton occurrences and ecological data. Imagery instruments can vary in the way they sample (benchtop or in situ imagers) and the particle’s size range they target (see Lombard et al. (2019) for an extensive comparison of instruments and specifications). However, due to the wide variety of instruments and their (automatic) output data and formats, it is challenging to integrate datasets that originate from different sources. For this reason, we developed recommendations for plankton imagery data management, which can promote the ability to make these datasets as FAIR (Findable, Accessible, Interoperable and Reusable principles), as possible. The workflow presented here could inspire other Biodiversity Information Standards TDWG communities working with (automated) imagery data (e.g., camera traps) such as the Audubon Core and Machine Observations Interest Group. The recommended data format follows the OBIS-ENV-DATA format (De Pooter et al. 2017), a Darwin Core-based approach to standardise biodiversity data (Wieczorek et al. 2012) used in EurOBIS, the European node of the Ocean Biodiversity Information System (OBIS) and EMODnet Biology, the European Marine Biodiversity Data Network. However, this format does not include sufficient information for imagery data, therefore we propose the use of additional Darwin Core terms. For example, by including the terms identifiedBy, identificationVerificationStatus and identificationReferences in the Occurrence table, more clarity is reported regarding the uncertainty of the classification made by an algorithm. Thus, data providers can publish manually validated datasets or datasets produced by fully automated plankton identification workflows; and users can choose to use validated or not validated data. See in Suppl. material 1 a practical example on how to report an imagery dataset following the best practices. Moreover, the OBIS-ENV-DATA format allows the ingestion of additional information thanks to the use of the Darwin Core (DwC) Extended Measurement Or Facts or eMoF extension in the DwC Event core. The eMoF stores biotic, abiotic and sampling measurements and facts that are related to the Event and Occurrence table. An important aspect of this extension is that it includes standardised terms and controlled vocabularies, such as the British Oceanographic Data Centre (BODC) vocabularies, to standardise parameters that are not covered by DwC. The advantages of these is to unambiguously report information and to include those measurements that cannot be reported in the Event and Occurrence table (e.g., reporting abundance or biomass of plankton), and that are crucial to investigate ecosystem functioning questions. As a consequence, biodiversity data aggregators can extend their scope beyond species occurrence data. Fig. 1 summarises a typical dataflow that goes from imagery data acquisition to publication in several steps: Images are cropped and classified with software. This can be done in EcoTaxa, a web application that allows users to taxonomically classify images of individual organisms. Data is formatted in OBIS-ENV-DATA format. This format can be exported from EcoTaxa through its API. Data is submitted to EurOBIS via the IPT (Integrated Publishing Toolkit). Data is quality controlled by the BioCheck tool. Data in EurOBIS can flow to EMODnet Biology, OBIS and GBIF (Global Biodiversity Information Facility). Images are cropped and classified with software. This can be done in EcoTaxa, a web application that allows users to taxonomically classify images of individual organisms. Data is formatted in OBIS-ENV-DATA format. This format can be exported from EcoTaxa through its API. Data is submitted to EurOBIS via the IPT (Integrated Publishing Toolkit). Data is quality controlled by the BioCheck tool. Data in EurOBIS can flow to EMODnet Biology, OBIS and GBIF (Global Biodiversity Information Facility). Plankton imagery instrument operators now have the possibility to format their data following the best practices and recommendations for plankton imagery data management (Martin-Cabrera et al. 2022). After a dataset is formatted following these guidelines, it can be submitted to the international biodiversity data aggregators, EurOBIS, EMODnet Biology and GBIF. Additionally a (semi) automated dataflow is presented where data providers can classify images in EcoTaxa and export the data in the required formats using an API before submission to EurOBIS. The next steps are to disseminate these best practices, encouraging plankton imagery data generators to implement these workflows to share their data easily, enriching these data portals and encouraging cross collaborations to create data products covering broader geographic scales and plankton species.

Siliceous Rhizaria (polycystine radiolarians and phaeodarians) are significant contributors to carbon and silicon biogeochemical cycles. Considering their broad taxonomic diversity and their wide size range (from a few micrometres up to several millimetres), a comprehensive evaluation of the entire community to carbon and silicon cycles is challenging. Here, we assess the diversity and contribution of silicified Rhizaria to the global biogenic silica stocks in the upper 500 m of the oligotrophic North-Western Mediterranean Sea using both imaging (FlowCAM, Zooscan and Underwater Vision Profiler) and molecular tools and data. While imaging data (cells m -3 ) revealed that the most abundant organisms were the smallest, molecular results (number of reads) showed that the largest Rhizaria had the highest relative abundances. While this seems contradictory, relative abundance data obtained with molecular methods appear to be closer to the total biovolume data than to the total abundance data of the organisms. This result reflects a potential link between gene copies number and the volume of a given cell allowing reconciling molecular and imaging data. Using abundance data from imaging methods we estimate that siliceous Rhizaria accounted for up to 6% of the total biogenic silica biomass of the siliceous planktonic community in the upper 500m of the water column.

Zooplankton plays a major role in ocean food webs and biogeochemical cycles, and provides major ecosystem services as a main driver of the biological carbon pump and in sustaining fish communities. Zooplankton is also sensitive to its environment and reacts to its changes. To better understand the importance of zooplankton, and to inform prognostic models that try to represent them, spatially-resolved biomass estimates of key plankton taxa are desirable. In this study we predict, for the first time, the global biomass distribution of 19 zooplankton taxa (1-50 mm Equivalent Spherical Diameter) using observations with the Underwater Vision Profiler 5, a quantitative in situ imaging instrument. After classification of 466,872 organisms from more than 3,549 profiles (0-500 m) obtained between 2008 and 2019 throughout the globe, we estimated their individual biovolumes and converted them to biomass using taxa-specific conversion factors. We then associated these biomass estimates with climatologies of environmental variables (temperature, salinity, oxygen, etc.), to build habitat models using boosted regression trees. The results reveal maximal zooplankton biomass values around 60°N and 55°S as well as minimal values around the oceanic gyres. An increased zooplankton biomass is also predicted for the equator. Global integrated biomass (0-500 m) was estimated at 0.403 PgC. It was largely dominated by Copepoda (35.7%, mostly in polar regions), followed by Eumalacostraca (26.6%) Rhizaria (16.4%, mostly in the intertropical convergence zone). The machine learning approach used here is sensitive to the size of the training set and generates reliable predictions for abundant groups such as Copepoda (R2 ≈ 20-66%) but not for rare ones (Ctenophora, Cnidaria, R2 < 5%). Still, this study offers a first protocol to estimate global, spatially resolved zooplankton biomass and community composition from in situ imaging observations of individual organisms. The underlying dataset covers a period of 10 years while approaches that rely on net samples utilized datasets gathered since the 1960s. Increased use of digital imaging approaches should enable us to obtain zooplankton biomass distribution estimates at basin to global scales in shorter time frames in the future.

In every liter of seawater there are between 10 and 100 billion life forms, mostly invisible, called marine plankton or marine microbiome, which form the largest and most dynamic ecosystem on our planet, at the heart of global ecological and economic processes. While physical and chemical parameters of planktonic ecosystems are fairly well measured and modeled at the planetary scale, biological data are still scarce due to the extreme cost and relative inflexibility of the classical vessels and instruments used to explore marine biodiversity. Here we introduce ‘Plankton Planet’, an initiative whose goal is to engage the curiosity and creativity of researchers, makers, and mariners to ( i ) co-develop a new generation of cost-effective (frugal) universal scientific instrumentation to measure the genetic and morphological diversity of marine microbiomes in context, ( ii ) organize their systematic deployment through coastal or open ocean communities of sea-users/farers, to generate uniform plankton data across global and long-term spatio-temporal scales, and ( iii ) setup tools to flow the data without embargo into public and explorable databases. As proof-of-concept, we show how 20 crews of sailors were able to sample plankton biomass from the world surface ocean in a single year, generating the first seatizen-based, planetary dataset of marine plankton biodiversity based on DNA barcodes. The quality of this dataset is comparable to that generated by Tara Oceans and is not biased by the multiplication of samplers. The data unveil significant genetic novelty and can be used to explore the taxonomic and ecological diversity of plankton at both regional and global scales. This pilot project paves the way for construction of a miniaturized, modular, evolvable, affordable and open-source citizen field-platform that will allow systematic assessment of the eco/morpho/genetic variation of aquatic ecosystems and microbiomes across the dimensions of the Earth system.

Vertical variations in physical and chemical conditions drive changes in marine zooplankton community composition. In turn, zooplankton communities play a critical role in regulating the transfer of organic matter produced in the surface ocean to deeper layers. Yet, the links between zooplankton community composition and the strength of vertical fluxes of particles remain elusive, especially on a global scale. Here, we provide a comprehensive analysis of variations in zooplankton community composition and vertical particle flux in the upper kilometer of the global ocean. Zooplankton samples were collected across five depth layers and vertical particle fluxes were assessed using continuous profiles of the Underwater Vision Profiler (UVP5) at 57 stations covering seven ocean basins. Zooplankton samples were analysed using a Zooscan and individual organisms were classified into 19 groups for the quantitative analyses. Zooplankton abundance, biomass and vertical particle flux decreased from the surface to 1000 m depth at all latitudes. The zooplankton abundance decrease rate was stronger at sites characterised by oxygen minima (<5µmol O₂.kg⁻¹) where most zooplankton groups showed a marked decline in abundance, except the jellyfishes, molluscs, annelids, large protists and a few copepod families. The attenuation rate of vertical particle fluxes was weaker at such oxygen-depleted sites. Canonical redundancy analyses showed that the epipelagic zooplankton community composition depended on the temperature, on the phytoplankton size distribution and the surface large particulate organic matter while oxygen was an additional important factor for structuring zooplankton in the mesopelagic. Our results further suggest that future changes in surface phytoplankton size and taxa composition and mesopelagic oxygen loss might lead to profound shift in zooplankton abundance and community structure in both the euphotic and mesopelagic ocean. These changes may affect the vertical export and hereby the strength of the biological carbon pump.

The Mediterranean Sea is recognized as one of the most polluted areas by floating plastics. During the Tara Mediterranean expedition, an extensive sampling of plastic debris was conducted in seven ecoregions, from Gibraltar to Lebanon with the aim of providing reliable estimates of regional differences in floating plastic loads and plastic characteristics. The abundance, size, surface, circularity and mass of 75,030 pieces were analyzed and classified in a standardized multi-parameter database. Their average abundance was 2.60 × 10⁵ items km⁻² (2.25 × 10³ to 8.50 × 10⁶ km⁻²) resulting in an estimate of about 650 billion plastic particles floating on the surface of the Mediterranean. This corresponds to an average of 660 metric tons of plastic, at the lower end of literature estimates. High concentrations of plastic were observed in the northwestern coastal regions, north of the Tyrrhenian Sea, but also off the western and central Mediterranean basins. The Levantine basin south of Cyprus had the lowest concentrations. A Lagrangian Plastic Pollution Index (LPPI) predicting the concentration of plastic debris was validated using the spatial resolution of the data. The advanced state of plastic degradation detected in the analyses led to the conclusion that stranding/fragmentation/resuspension is the key process in the dynamics of floating plastic in Mediterranean surface waters. This is supported by the significant correlation between pollution sources and areas of high plastic concentration obtained by the LPPI.

The oceans represent 97% of all water on Earth and contain microscopic, drifting life, plankton, which drives global biogeochemical cycles. A major hurdle in assessing marine plankton is the planetary scale of the oceans and the logistical and economic constraints associated with their sampling. This difficulty is reflected in the limited amount of scientifically equipped fleets and affordable equipment. Here we present a modular hardware/software open-source strategy for building a versatile, re-configurable imaging platform - the PlanktoScope - that can be adapted to a number of applications in aquatic biology and ecology. We demonstrate high-throughput quantitative imaging of laboratory and field plankton samples while enabling rapid device reconfiguration to match the evolving needs of the sampler. The presented versions of PlanktoScope are capable of autonomously imaging 1.7 ml per minute with a 2.8 µm/px resolution and can be controlled from any WiFi-enabled device. The PlanktoScope’s small size, ease of use, and low cost - under $1000 in parts - enable its deployment for customizable monitoring of laboratory cultures or natural micro-plankton communities. This also paves the way toward consistent and long-term measurement of plankton diversity by an international fleet of citizen vessels at the planetary scale.

Phytoplankton account for >45% of global primary production, and have an enormous impact on aquatic food webs and on the entire Earth System. Their members are found among prokaryotes (cyanobacteria) and multiple eukaryotic lineages containing chloroplasts. Genetic surveys of phytoplankton communities generally consist of PCR amplification of bacterial (16S), nuclear (18S) and/or chloroplastic (16S) rRNA marker genes from DNA extracted from environmental samples. However, our appreciation of phytoplankton abundance or biomass is limited by PCR-amplification biases, rRNA gene copy number variations across taxa, and the fact that rRNA genes do not provide insights into metabolic traits such as photosynthesis. Here, we targeted the photosynthetic gene psbO from metagenomes to circumvent these limitations: the method is PCR-free, and the gene is universally and exclusively present in photosynthetic prokaryotes and eukaryotes, mainly in one copy per genome. We applied and validated this new strategy with the size-fractionated marine samples collected by Tara Oceans, and showed improved correlations with flow cytometry and microscopy than when based on rRNA genes. Furthermore, we revealed unexpected features of the ecology of these ecosystems, such as the high abundance of picocyanobacterial aggregates and symbionts in the ocean, and the decrease in relative abundance of phototrophs towards the larger size classes of marine dinoflagellates. To facilitate the incorporation of psbO in molecular-based surveys, we compiled a curated database of >18,000 unique sequences. Overall, psbO appears to be a promising new gene marker for molecular-based evaluations of entire phytoplankton communities.

A major challenge in characterizing plankton communities is the collection, identification and quantification of samples in a time-efficient way. The classical manual microscopy counts are gradually being replaced by high throughput imaging and nucleic acid sequencing. DNA sequencing allows deep taxonomic resolution (including cryptic species) as well as high detection power (detecting rare species), while RNA provides insights on function and potential activity. However, these methods are affected by database limitations, PCR bias, and copy number variability across taxa. Recent developments in high-throughput imaging applied in situ or on collected samples (high-throughput microscopy, Underwater Vision Profiler, FlowCam, ZooScan, etc) has enabled a rapid enumeration of morphologically-distinguished plankton populations, estimates of biovolume/biomass, and provides additional valuable phenotypic information. Although machine learning classifiers generate encouraging results to classify marine plankton images in a time efficient way, there is still a need for large training datasets of manually annotated images. Here we provide workflow examples that couple nucleic acid sequencing with high-throughput imaging for a more complete and robust analysis of microbial communities. We also describe the publicly available and collaborative web application EcoTaxa, which offers tools for the rapid validation of plankton by specialists with the help of automatic recognition algorithms. Finally, we describe how the field is moving with citizen science programs, unmanned autonomous platforms with in situ sensors, and sequencing and digitalization of historical plankton samples.

To obtain a proxy for the stress level of collected corals, we checked for previous occurrences of bleaching events at sampled reef sites by matching island GPS coordinates to the Reef Check dataset (reefcheck.org) obtained from Sully et al (2019). For each Tara Pacific island coordinate, we determined the Reef Check site that was closest (in terms of distance in km); we only considered Reef Check data that was within a 10 km circumference. We further determined short- and long-term climate variables that are known to affect coral stress resilience for all Tara Pacific collection sites that are available from Lombard et al (2022). These data allow to assess if corals from a given site were exposed higher/lower prevalence of thermal stress events and bleaching prior to sampling (over previous years).

Abstract Coral reefs are of paramount importance in marine ecosystems, where they provide support for a large part of the biodiversity. Being quite sensitive to global changes, they are therefore the prime targets for biodiversity conservation policies. However, such conservation goals require accurate species identification, which are notoriously difficult to get in these highly morphologically variable organisms, rich in cryptic species. There is an acute need for easy-to-use and resolutive species diagnostic molecular markers. The present study builds on the huge sequencing effort developed during the TARA Pacific expedition to develop a genotyping strategy to assign coral samples to the correct species within two coral genera ( Porites and Pocillopora ). For this purpose, we developed a technique that we called “Divergent Fragment” based on the sequencing of a less than 2kb long diagnostic genomic fragment determined from the metagenomic data of a subset of the corals collected. This method has proven to be rapid, resolvable and cost-effective. Sequencing of PCR fragments nested along the species diagnostic fragment allowed us to assign 232 individuals of the genus Pocillopora and 247 individuals of the genus Porites to previously identified independent genetic lineages ( i . e . species). This genotyping method will allow to fully analyze the coral samples collected across the Pacific during the Tara Pacific expedition and opens technological perspectives in the field of population genomics-guided conservation.

Marine particles of different nature are found throughout the global ocean. The term “marine particles” describes detritus aggregates and fecal pellets as well as bacterioplankton, phytoplankton, zooplankton and nekton. Here, we present a global particle size distribution dataset obtained with several Underwater Vision Profiler 5 (UVP5) camera systems. Overall, within the 64 µm to about 50 mm size range covered by the UVP5, detrital particles are the most abundant component of all marine particles; thus, measurements of the particle size distribution with the UVP5 can yield important information on detrital particle dynamics. During deployment, which is possible down to 6000 m depth, the UVP5 images a volume of about 1 L at a frequency of 6 to 20 Hz. Each image is segmented in real time, and size measurements of particles are automatically stored. All UVP5 units used to generate the dataset presented here were inter-calibrated using a UVP5 high-definition unit as reference. Our consistent particle size distribution dataset contains 8805 vertical profiles collected between 19 June 2008 and 23 November 2020. All major ocean basins, as well as the Mediterranean Sea and the Baltic Sea, were sampled. A total of 19 % of all profiles had a maximum sampling depth shallower than 200 dbar, 38 % sampled at least the upper 1000 dbar depth range and 11 % went down to at least 3000 dbar depth. First analysis of the particle size distribution dataset shows that particle abundance is found to be high at high latitudes and in coastal areas where surface productivity or continental inputs are elevated. The lowest values are found in the deep ocean and in the oceanic gyres. Our dataset should be valuable for more in-depth studies that focus on the analysis of regional, temporal and global patterns of particle size distribution and flux as well as for the development and adjustment of regional and global biogeochemical models. The marine particle size distribution dataset (Kiko et al., 2021) is available at https://doi.org/10.1594/PANGAEA.924375.

Marine plankton mitigate anthropogenic greenhouse gases, modulate biogeochemical cycles, and provide fishery resources. Plankton is distributed across a stratified ecosystem of sunlit surface waters and a vast, though understudied, mesopelagic ‘dark ocean’. In this study, we mapped viruses, prokaryotes, and pico-eukaryotes across 32 globally-distributed cross-depth samples collected during the Tara Oceans Expedition, and assessed their ecologies. Based on depth and O 2 measurements, we divided the marine habitat into epipelagic, oxic mesopelagic, and oxygen minimum zone (OMZ) eco-regions. We identified specific communities associated with each marine habitat, and pinpoint environmental drivers of dark ocean communities. Our results indicate that water masses primarily control mesopelagic community composition. Through co-occurrence network inference and analysis, we identified signature communities strongly associated with OMZ eco-regions. Mesopelagic communities appear to be constrained by a combination of factors compared to epipelagic communities. Thus, variations in a given abiotic factor may cause different responses in sunlit and dark ocean communities. This study expands our knowledge about the ecology of planktonic organisms inhabiting the mesopelagic zone.

<p>PHOTO dataset (<em>in situ</em> photos) and the colony morphometric analysis using <em>in situ </em>photographs of two scleractinian corals and one hydrozoan coral taken during the TARA Pacific Expedition: <em>Pocillopra </em>spp., <em>Porites </em>spp. and <em>Millepora </em>spp. respectively.</p>

Abstract Sea spray aerosol (SSA) formation have a major role in the climate system, but measurements at a global-scale of this micro-scale process are highly challenging. We measured high-resolution temporal patterns of SSA number concentration over the Atlantic Ocean, Caribbean Sea, and the Pacific Ocean covering over 42,000 km. We discovered a ubiquitous 24-hour rhythm to the SSA number concentration, with concentrations increasing after sunrise, remaining higher during the day, and returning to predawn values after sunset. The presence of dominating continental aerosol transport can mask the SSA cycle. We did not find significant links between the diel cycle of SSA number concentration and diel variations of surface winds, atmospheric physical properties, radiation, pollution, nor oceanic physical properties. However, the daily mean sea surface temperature positively correlated with the magnitude of the day-to-nighttime increase in SSA concentration. Parallel diel patterns in particle sizes were also detected in near-surface waters attributed to variations in the size of particles smaller than ~1 µm. These variations may point to microbial day-to-night modulation of bubble-bursting dynamics as a possible cause of the SSA cycle.

Plankton imaging instruments generate an ever increasing volume of data which is mostly processed through machine learning algorithms. However, classifying plankton images is a challenging computer science task in its own right: datasets are strongly unbalanced; the dominant classes are often not biologically interesting (artefacts, bubbles) and/or very heterogeneous looking (marine snow); and images span a large size range. Despite a wealth of reports on the performance of automatic plankton images classifiers, we still do not have a definitive idea regarding how methods compare with each other and where they can systematically be trusted. This is mostly because those reports rely on rather small unpublished datasets, not necessarily representative of real-life biological samples in terms of size, number of categories and proportions. Here we report the performance of a classic classification method (Random Forest on handcrafted image features) and a more recent one (a Convoluted Neural Network) on large publicly released datasets, from five widely used plankton imaging instruments. We show that CNN improve classification performance but only noticeably on poorly represented (a few hundred images) classes. Finally, we showcase the difference between the predictions of the two classifiers and a human-checked truth on several real-world datasets, to give insights regarding which ecological questions can or cannot be studied from computer-generated classifications only.

Nitrogen fixation has a critical role in marine primary production, yet our understanding of marine nitrogen-fixers (diazotrophs) is hindered by limited observations. Here, we report a quantitative image analysis pipeline combined with mapping of molecular markers for mining >2,000,000 images and >1300 metagenomes from surface, deep chlorophyll maximum and mesopelagic seawater samples across 6 size fractions (<0.2-2000 μm). We use this approach to characterise the diversity, abundance, biovolume and distribution of symbiotic, colony-forming and particle-associated diazotrophs at a global scale. We show that imaging and PCR-free molecular data are congruent. Sequence reads indicate diazotrophs are detected from the ultrasmall bacterioplankton (<0.2 μm) to mesoplankton (180-2000 μm) communities, while images predict numerous symbiotic and colony-forming diazotrophs (>20 µm). Using imaging and molecular data, we estimate that polyploidy can substantially affect gene abundances of symbiotic versus colony-forming diazotrophs. Our results support the canonical view that larger diazotrophs (>10 μm) dominate the tropical belts, while unicellular cyanobacterial and non-cyanobacterial diazotrophs are globally distributed in surface and mesopelagic layers. We describe co-occurring diazotrophic lineages of different lifestyles and identify high-density regions of diazotrophs in the global ocean. Overall, we provide an update of marine diazotroph biogeographical diversity and present a new bioimagingbioinformatic workflow.

A Correction to this paper has been published: https://doi.org/10.1038/s43247-021-00119-5

The development of a new generation of biological sensors has drastically changed the studies of marine plankton from lab bench work to in vivo and real-time observations. Target organisms, from bacteria to plankton, can now be optically characterized and/or photographed and archived. Consequently, scientists are facing the difficult challenge to handle a large amount of data which need to be processed rapidly and harmonised before being stored in databases to be accessible to scientific/environmental management communities. In the Joint European Research Infrastructure for Coastal Observatories (JERICO-RI), we intend to integrate the monitoring of physical, biogeochemical and biological variables to better understand coastal ecosystems. Focusing primarily on plankton communities measured at high spatial and temporal resolution, we aim to provide a framework for the data flow following the Findability, Accessibility, Interoperability, and Reuse (FAIR). To achieve this, we need to draw up best practices in data management to be followed by users and experts operating the sensors such as standardised protocol, minimal technical metadata elements for effective re-use, identify and extend appropriate vocabularies, identify tools for data integration and platforms for trust-worthy long-term archival, standardised data formats to be ingested by European data infrastructures. In this presentation, we will present some of our achievements regarding in vivo flow cytometry, imagery analysis, and multispectral fluorimetry.

Invasion rates have increased in the past 100 y irrespective of international conventions. What characterizes a successful invasion event? And how does genetic diversity translate into invasion success? Employing a whole-genome perspective using one of the most successful marine invasive species world-wide as a model, we resolve temporal invasion dynamics during independent invasion events in Eurasia. We reveal complex regionally independent invasion histories including cases of recurrent translocations, time-limited translocations, and stepping-stone range expansions with severe bottlenecks within the same species. Irrespective of these different invasion dynamics, which lead to contrasting patterns of genetic diversity, all nonindigenous populations are similarly successful. This illustrates that genetic diversity, per se, is not necessarily the driving force behind invasion success. Other factors such as propagule pressure and repeated introductions are an important contribution to facilitate successful invasions. This calls into question the dominant paradigm of the genetic paradox of invasions, i.e., the successful establishment of nonindigenous populations with low levels of genetic diversity.

Abstract Ocean plankton comprise organisms from viruses to fish larvae that are fundamental to ecosystem functioning and the provision of marine services such as fisheries and CO 2 sequestration. The latter services are partly governed by variations in plankton community composition and the expression of traits such as body size at community-level. While community assembly has been thoroughly studied for the smaller end of the plankton size spectrum, the larger end comprises ectotherms that are often studied at the species, or group-level, rather than as communities. The body size of marine ectotherms decreases with temperature, but controls on community-level traits remain elusive, hindering the predictability of marine services provision. Here, we leverage Tara Oceans datasets to determine how zooplankton community composition and size structure varies with latitude, temperature and productivity-related covariates in the global surface ocean. Zooplankton abundance and median size decreased towards warmer and less productive environments, as a result of changes in copepod composition. However, some clades displayed the opposite relationships, which may be ascribed to alternative feeding strategies. Given that climate models predict increasingly warmed and stratified oceans, our findings suggest that zooplankton communities will shift towards smaller organisms which might weaken their contribution to the biological carbon pump.

As phytoplankton is essential in supporting food webs and mediating biogeochemical cycles, it became crucial to complement discrete sampling and laboratory methods to address this compartment at its finest temporal and spatial scale. Within the “Joint European Research Infrastructure for Coastal Observatories – Novel EXperTise” (JERICO-NEXT), scientists proceeded to the exploration of novel phytoplankton automated in vivo/in situ techniques, based on single cell/particle or bulk optical characteristics. These techniques were implemented in a variety of monitoring platforms (fixed stations, moorings, research vessels, ships of opportunity), from oligotrophic (West Mediterranean) to mesotrophic and eutrophic marine coastal waters (English Channel, North Sea and Baltic Sea). These approaches could represent warning systems in water quality through phytoplankton total abundance and biomass, composition changes and the occurrence of blooms, including harmful algal blooms HAB, of special interest in areas of fishing, aquaculture and tourism. At the dawn of the UN Decade of the Ocean, the JERICO-S3 (Science, Services, Sustainability) project tends to generalise these approaches and seeks to standardise as much as possible their operability and capacity in addressing phytoplankton diversity and productivity, moving towards a new approach of Essential Ocean Variables (EOVs). Moreover, the development of automated tools for data analysis, using machine-learning and deep learning and will allow integrating these data into European marine data infrastructures available for research and marine management.

Marine biodiversity is a fundamental characteristic of our planet that depends on and influences climate, water quality, and many ocean state variables. It is also at the core of ecosystem services that can make or break economic development in any region. Our purpose is to highlight the need for marine biological observations to inform science and conservation management and to support the blue economy. We provide ten recommenda-tions, applicable now, to measure and forecast biological Essential Ocean Variables (EOVs) as part of economic monitoring efforts. The UN Decade of Ocean Science for Sustainable Development (2021–2030) provides a timely opportunity to implement these recommendations to benefit humanity and enable the USD 3 trillion global ocean economy expected by 2030.

Aquatic ecologists face challenges in identifying the general rules of the functioning of ecosystems. A common framework, including freshwater, marine, benthic, and pelagic ecologists is needed to bridge communication gaps and foster knowledge sharing. This framework should transcend local specificities and taxonomy in order to provide a common ground and shareable tools to address common scientific challenges. Here, we advocate the use of functional trait-based approaches (FTBAs) for aquatic ecologists, and propose concrete paths to go forward. Firstly, we propose to unify existing definitions in FTBAs to adopt a common language. Secondly, we list the numerous databases referencing functional traits for aquatic organisms. Thirdly, we present a synthesis on traditional as well as recent promising methods for the study of aquatic functional traits, including imaging and genomics. Finally, we conclude with a highlight on scientific challenges and promising venues for which FTBAs should foster opportunities for future research. By offering practical tools, our framework provides a clear path forward to the adoption of trait-based approaches in aquatic ecology.

This data is the result of the primary analysis of the V9 18S rDNA metabarcoding sequencing data from the Tara Pacific expedition. The analysis was conducted using cutadapt, vsearch, swarm and lulu. Please refer to the readme file for more details.

<p>This data is the result of the primary analysis of the Symbiodiniaceae ITS2 rDNA gene sequencing data collected from all islands as part of the Tara Pacific expedition.The analysis was conducted using SymPortal. A full README is contained within the data upload.</p>

While Ocean modeling has made significant advances over the last decade, its complex biological component is still oversimplified. In particular, modeling organisms in the ocean system must integrate parameters to fit both physiological and ecological behaviors that are together very difficult to determine. Such difficulty occurs for modeling Pelagia noctiluca. This jellyfish has a high abundance in the Mediterranean Sea and could contribute to several biogeochemical processes. However, gelatinous zooplanktons remain poorly represented in biogeochemical models because uncertainties about their ecophysiology limit our understanding of their potential role and impact. To overcome this issue, we propose, for the first time, the use of the Statistical Model Checking Engine (SMCE), a probabilitybased computational framework that considers a set of parameters as a whole. Contrary to standard parameter inference techniques, SMCE identifies sets of parameters that fit both laboratory-culturing observations and in situ patterns while considering uncertainties. Doing so, we estimated the best parameter sets of the ecophysiological model that represents the jellyfish growth and degrowth in laboratory conditions as well as its size. Behind this application, SMCE remains a computational framework that supports the projection of a model with uncertainties in broader contexts such as biogeochemical processes to drive future studies.

Abstract The planktonic communities within our oceans represent one of the most diverse and understudied ecosystems on the planet. A major hurdle in describing these systems is the sheer scale of the oceans along with logistical and economic constraints associated with their sampling. This is due to the limited amount of scientifically equipped fleets and affordable equipment. Here we demonstrate a modular approach for building a versatile, re-configurable imaging platform that can be adapted to a number of field applications, specifically focusing on oceanography. By using a modular hardware/software approach for building microscopes, we demonstrate high-throughput imaging of lab and field samples while enabling rapid device reconfiguration in order to match diverse applications and the evolving needs of the sampler. The presented versions of PlanktonScope are capable of autonomously imaging 1.7 ml per minute with a 1.5 µm resolution, and are built with under $400 in parts. This low cost enables new applications in laboratory settings such as the continuous imaging of suspension cultures, and in-field settings with the ability to scale up for long-term deployment on an international fleet of sailing boats enabling citizens based oceanographic research

<p>This data is the result of the primary analysis of the 16S rRNA gene sequencing data collected from all islands as part of the Tara Pacific expedition. The analysis was conducted using cutadapt/snakemake/dada2 and usearch. A full README is contained within the data upload.</p>

<p>The tables in this dataset associate metabarcoding sequencing files generated by Genoscope (i.e. fastq.gz files with informative filename structures; with sequencing file pairs associated to unique 'readset' identifiers; housed on their FTP server at www.genoscope.cns.fr/sadc/tarapacific/METABARCODING; with the 'METAB' sequence strategy identifier as part of the sequencing file name) with their associated 'sample-id_source' identifier; as detailed in the 'TARA-PACIFIC_samples-provenance' file part of the 'Tara Pacific samples provenance and environmental context' Zenodo publication (DOI: 10.5281/zenodo.4068292) part of the 'tarapacific' Zenodo community). The main purpose of these tables is to act as a reference to identify samples (i.e., with a single 'sample-id_source') for which sequencing replication exists, per primer set (i.e., more than one set of fastq.gz sequencing files were generated, pre primer set). In the case of replication, these tables classify the replication into three classes color coded as green (same DNA extraction, same PCR, same sequencing run, different sequencing lane), yellow (same DNA extraction, same PCR, different sequencing run) and red (different DNA extraction and/or different PCR). It should be noted that in the vast majority of cases a 'sample-id_source' associates to only one readset per primer set. For a full description of the dataset, please see the included README.</p>

E536 ABSTRACT: Marine aerosols play a significant role in the global radiative budget, in clouds' processes , and in the chemistry of the marine atmosphere. There is a critical need to better understand their production mechanisms, composition, chemical properties, and the contribution of ocean-derived biogenic matter to their mass and number concentration. Here we present an overview of a new dataset of in situ measurements of marine aerosols conducted over the 2.5-yr Tara Pacific Expedition over 110,000 km across the Atlantic and Pacific Oceans. Preliminary results are presented here to describe the new dataset that will be built using this novel set of measurements. It will characterize marine aerosols properties in detail and will open a new window to study the marine aerosol link to the water properties and environmental conditions.

Abstract In every liter of seawater there are between 10 and 100 billion life forms, mostly invisible, called plankton, which form the largest and most dynamic ecosystem on our planet, at the heart of global ecological and economic processes. While physical and chemical parameters of planktonic ecosystems are fairly well measured and modelled at the planetary scale, but biological data are still scarce due to the extreme cost and relative inflexibility of the classical vessels and instruments used to explore marine biodiversity. Here we introduce ‘ Plankton Planet ’, an initiative whose goal is to merge the creativity of researchers, makers, and mariners to ( i ) develop frugal scientific instrumentation and protocols to assess the genetic and morphological diversity of plankton life, and ( ii ) organize their systematic deployment through fleets of volunteer sailors, fishermen, or cargo-ships to generate comparable and open-access plankton data across global and long-term spatio-temporal scales. As proof-of-concept, we show how 20 crews of sailors (“planktonauts”) were abl to sample plankton biomass from the world surface ocean in a single year, generating the first citizen-based, planetary dataset of plankton biodiversity based on DNA barcodes. The quality of this dataset is comparable to that generated by Tara Oceans and is not biased by the multiplication of samplers. This dataset has unveiled significant genetic novelty and can be used to explore the taxonomic and ecological diversity of plankton at both regional and global scales. This pilot project paves the way for construction of a miniaturized, modular, evolvable, affordable and open-source citizen field-platform that will allow systematic assessment of the eco/morpho/genetic variation of aquatic ecosystems across the dimensions of the Earth system.

Anthropogenic pollution from marine microplastic particles is a growing concern, both as a source of toxic compounds, and because they can transport pathogens and other pollutants. Airborne microplastic particles were previously observed over terrestrial and coastal locations, but not in the remote ocean. Here, we collected ambient aerosol samples in the North Atlantic Ocean, including the remote marine atmosphere, during the Tara Pacific expedition in May-June 2016, and chemically characterized them using micro-Raman spectroscopy. We detected a range of airborne microplastics, including polystyrene, polyethylene, polypropylene, and poly-silicone compounds. Polyethylene and polypropylene were also found in seawater, suggesting local production of airborne microplastic particles. Terminal velocity estimations and back trajectory analysis support this conclusion. For technical reasons, only particles larger than 5 µm, at the upper end of a typical marine atmospheric size distribution, were analyzed, suggesting that our analyses underestimate the presence of airborne microplastic particles in the remote marine atmosphere.

In recent years, autonomous platforms have been improved with the objective of observing the deep ocean. Many prototypes have reached 6,000 m, but only a few are commercially available. Imaging sensors have been developed to study the numbers, sizes and shapes of particles and plankton. These have been deployed independently or mounted on CTD rosettes (e.g. the UVP5 Underwater Vision Profiler). In some areas, they observed high concentrations of large particles down to the bottom of the ocean, showing intense carbon export. They also documented the presence of fragile organisms, such as rhizarians, whose key ecological roles in the ocean was unknown until then. The new miniaturized UVP6-LP (Low Power) sensor, developed to be mounted on autonomous platforms, is complementary to the larger sensors deployed on CTD rosettes. It also records and identifies particles and plankton, using imagery. It counts and sizes particles \textgreater80 µM ESD and identifies large aggregates and plankton \textgreater700µM ESD. This, at low cost and with very low power. Six prototypes of the sensor have been inter-calibrated with the reference UVP5. The instrument can be deployed down to 6,000 m, which corresponds to 97% of the ocean surface. A UVP6-LP was used to quantify particles released from a deep-sea mining experiment at 4,300 m. Others performed transects on gliders and vertical profiles on a float. A UVP6-LP was moored for one year at 50 m at 82°N. Other UVP6-LP will be deployed on the a cabled observatory in the Mediterranean Sea at 2,200 m, and on the SeaCycler mooring in the Labrador Sea. The very low power required for the operation of the UVP6-LP allows to optimize its use on profiling floats and gliders. Autonomous platforms cannot transmit images due to the limitation of satellite bandwidth or acoustic telemetry. To overcome this limitation, the UVP6-LP includes an embedded algorithm for the automatic classification of large aggregates and plankton images, which provides data that are accurate enough for monitoring programs and scientific studies. Because scientists, policy makers and the public require easy access to data, a complete software ecosystem is used to pilot the instrument, record the data, and make them freely available to the scientists and the public. When the instruments are recovered after deployment, their data include classified images.

<p>This dataset contains 4 tables and 3 sets of figures related to the primary analysis of the 18S metabarcoding sequencing output. This dataset is only concerned with the identity of the coral host (i.e. not additional protist diversity). The samples included in this dataset have a 'sample-material_label' value of 'CORAL' and 'sampling-protocol_label' value of 'SEQ-CS4L'. They represent the coral samples collected at all 32 of the islands visited in the Tara Pacific expedition.</p>

“Imagery data” can be referred as qualitative and quantitative information from a collection of images. Imaging systems are used more and more frequently in the marine domain to generate huge amounts of imagery data. For example, automatic image classification is used to determine the abundance, size and biomass of plankton communities. In addition, the recent advances of imaging sensors and the growing datasets, highlight the importance of the management and storage capacity of these data. Thus, establishing data standards, optimized data flows and quality control procedures will promote the ability to make these datasets findable, accessible, interoperable and reusable (FAIR principles).At the moment, there are a number of online open-access databases that collect marine biodiversity data, such as the Ocean Biodiversity Information System (OBIS), and more specialized in plankton observations such as the COPEPOD for plankton biomass and ECOTAXA for taxonomic annotation of plankton images. However, they currently lack relevant standards to link metadata of the images.International biodiversity data standards, such as Darwin Core (DwC), are already widely used in OBIS and the Global Biodiversity Information Facility (GBIF). OBIS, has recently adopted the OBIS-ENV-DATA, a format that follows the DwC-Archive (DwC-A) standard, consisting of a DwC Event table in combination with an Occurrence an extended Measurement or Fact table. This structure enables the linkage of quantitative and qualitative properties to both sampling events and species occurrences. It also includes additional fields for property standardization, such as the BODC (British Oceanographic Data Centre) controlled vocabularies, the World Register of Marine Species (WoRMS), which provides crucial quality control support for taxonomic data, and Marine Regions, a database that provides standardized marine georeferenced place names and areas. However, there are no clear guidelines on how to include imagery metadata and derived data in OBIS-ENV-DATA.During this TDWG 2020 symposium, we would like to present and discuss our ongoing work to establish best practices and standardized protocols for imaging data and metadata acquired by a large spectrum of bio-optic sensors. Furthermore, we highlight how the integration of the metadata will flow to existing biodiversity data portals, the European EMODnet Biology portal, (EurOBIS) and OBIS.

Coral reefs are the most diverse habitats in the marine realm. Their productivity, structural complexity, and biodiversity critically depend on ecosystem services provided by corals that are threatened because of climate change effects—in particular, ocean warming and acidification. The coral holobiont is composed of the coral animal host, endosymbiotic dinoflagellates, associated viruses, bacteria, and other microeukaryotes. In particular, the mandatory photosymbiosis with microalgae of the family Symbiodiniaceae and its consequences on the evolution, physiology, and stress resilience of the coral holobiont have yet to be fully elucidated. The functioning of the holobiont as a whole is largely unknown, although bacteria and viruses are presumed to play roles in metabolic interactions, immunity, and stress tolerance. In the context of climate change and anthropogenic threats on coral reef ecosystems, the Tara Pacific project aims to provide a baseline of the “-omics” complexity of the coral holobiont and its ecosystem across the Pacific Ocean and for various oceanographically distinct defined areas. Inspired by the previous Tara Oceans expeditions, the Tara Pacific expedition (2016–2018) has applied a pan-ecosystemic approach on coral reefs throughout the Pacific Ocean, drawing an east–west transect from Panama to Papua New Guinea and a south–north transect from Australia to Japan, sampling corals throughout 32 island systems with local replicates. Tara Pacific has developed and applied state-of-the-art technologies in very-high-throughput genetic sequencing and molecular analysis to reveal the entire microbial and chemical diversity as well as functional traits associated with coral holobionts, together with various measures on environmental forcing. This ambitious project aims at revealing a massive amount of novel biodiversity, shedding light on the complex links between genomes, transcriptomes, metabolomes, organisms, and ecosystem functions in coral reefs and providing a reference of the biological state of modern coral reefs in the Anthropocene.

Interactions between the ocean and the atmosphere occur at the air-sea interface through the transfer of momentum, heat, gases and particulate matter, and through the impact of the upper-ocean biology on the composition and radiative properties of this boundary layer. The Tara Pacific expedition, launched in May 2016 aboard the schooner Tara, was a 29-month exploration with the dual goals to study the ecology of reef ecosystems along ecological gradients in the Pacific Ocean and to assess inter-island and open ocean surface plankton and neuston community structures. In addition, key atmospheric properties were measured to study links between the two boundary layer properties. A major challenge for the open ocean sampling was the lack of ship-time available for work at "stations". The time constraint led us to develop new underway sampling approaches to optimize physical, chemical, optical, and genomic methods to capture the entire community structure of the surface layers, from viruses to metazoans in their oceanographic and atmospheric physicochemical context. An international scientific consortium was put together to analyze the samples, generate data, and develop datasets in coherence with the existing Tara Oceans database. Beyond adapting the extensive Tara Oceans sampling protocols for high-resolution underway sampling, the key novelties compared to Tara Oceans' global assessment of plankton include the measurement of (i) surface plankton and neuston biogeography and functional diversity; (ii) bioactive trace metals distribution at the ocean surface and metal-dependent ecosystem structures; (iii) marine aerosols, including biological entities; (iv) geography, nature and colonization of microplastic; and (v) high-resolution underway assessment of net community production via equilibrator inlet mass spectrometry. We are committed to share the data collected during this expedition, making it an important resource important resource to address a variety of scientific questions.

Salps are gelatinous planktonic suspension feeders that filter large volumes of water in the food-dilute open ocean. Their life cycle allows periodic exponential growth and population blooms. Dense swarms of salps have a high grazing impact that can deplete the photic zone of phytoplankton and export huge quantities of organic matter to the deep sea. Previous studies described their feeding manner as mostly nonselective, with larger particles retained at higher efficiencies than small particles. To examine salp diets, we used direct in situ sampling (InEx method) of undisturbed solitary Salpa maxima. Aggregates ("chains") of Salpa fusiformis and Thalia democratica were studied using in situ incubations. Our findings suggest that in situ feeding rates are higher than previously reported and that cell removal is size independent with $ 1 μm picoeukaryotes preferentially removed over both larger eukaryotes and smaller bacteria. The prey : predator size ratios we measured (1 : 10 4-1 : 10 5) are an order of magnitude smaller than previously reported values and to the best of our knowledge, are the smallest values reported so far for any planktonic suspension feeders. Despite differences among the three species studied, they had similar prey preferences with no correlation between salp body length and prey size. Our findings shed new light on prey : predator relationships in planktonic systems-in particular, that factors other than size influence filtration efficiency-and suggest that in situ techniques should be devised and applied for the study of suspension feeding in the ocean.

Marine Protected Areas have become a major tool for the conservation of marine biodiversity and resources. Yet our understanding of their efficacy is often limited because it is measured for a few biological components, typically top predators or species of commercial interest. To achieve conservation targets, marine protected areas can benefit from ecosystem-based approaches. Within such an approach, documenting the variation of plankton indicators and their covariation with climate is crucial as plankton represent the base of the food webs. With this perspective, we sought to document the variations in the emerging properties of the plankton to better understand the dynamics of the pelagic fishes, mammals and seabirds that inhabit the region. For the first time, we analyze the temporal variations of the entire plankton community of one of the widest European protected areas, the Parc Naturel Marin de la Mer d’Iroise. We used data from several sampling transects carried out in the Iroise Sea from 2011 to 2015 to explore the seasonal and inter-annual variations of phytoplankton and mesozooplankton abundance, composition and size, as well as their covariation with abiotic variables, through multiple multivariate analyses. Overall, our observations are coherent with the plankton dynamics that have been observed in other regions of the North-East Atlantic. We found that both phytoplankton and zooplankton show consistent seasonal patterns in taxonomic composition and size structure but also display inter-annual variations. The spring bloom was associated with a higher contribution of large chain-forming diatoms compared to nanoflagellates, the latter dominating in fall and summer. Dinoflagellates show marked inter-annual variations in their relative contribution. The community composition of phytoplankton has a large impact on the mesozooplankton together with the distance to the coast. The size structure of the mesozooplankton community, examined through the ratio of small to large copepods, also displays marked seasonal patterns. We found that larger copepods (members of the Calanidae) are more abundant in spring than in summer and fall. We propose several hypotheses to explain the observed temporal patterns and we underline their importance for understanding the dynamics of other components of the food-web (such as sardines). Our study is a first step toward the inclusion of the planktonic compartment into the planning of the resources and diversity conservation within the Marine Protected Area.

Plankton plays a key role in the biological pump and has a big impact on marine living resources. However, plankton is difficult to observe in a consistent manner across its extended size range and by the multiple observers that uses protocols that are not inter calibrated. Imaging sensors have the potential to provide key ``ecosystem essential ocean variables'' eEOVs (plankton biodiversity, morphological traits) that complement other sensors such as optical ones. Lab and in-situ imaging sensors have been deployed the 10 last years to provide insights into local dynamics in the frame of time series programs (from daily to decadal scales) and during oceanographic surveys across ocean basins. Combining observations from the different programmes has sometimes allowed to detect concomitant changes in different areas or provide a better spatial distribution of plankton communities. For example, such efforts were supported by the European FP7 JERICO, H2020 JERICO-NEXT, BRIDGES, EURO-BASIN programs. Most of the observation efforts were performed independently and hundreds of millions of images have been collected (and billions to come as sensors are getting more available). All those sparsely distributed images are usually not available for the users because of limited development in software solutions for identification, archiving and distribution, which are in a current improving process. Several attempts for developing web based services for image recognition, distribution and archiving have been performed (ecotaxa.obs-vlfr.fr) but only a fraction of the existing and future data can be treated by them. Based on the past ten years of effort, we will present a synthesis of successful developments in using imaging systems to provide information on plankton community at local, regional and ultimately global scales. These examples will show how relevant they are for ecosystem monitoring (e.g. detection of ecosystem changes and regime-shifts) and services (e.g. aquaculture, fisheries, biological carbon pump). We will then build on these examples to discuss future developments with the aim of, better observing, harmonizing practices and developing state of the art marine data and information management in order to increase the connection with the relevant stakeholders and community of users among researchers, conservation managers and private companies.

In spite of the paramount ecological and socioeconomic relevance of tropical reef ecosystems, the dynamics of their meroplankton abundance remain poorly characterized. The small-scale distribution and detailed analysis of individual biomass of mesozooplankton were studied in the coastal reefs of Tamandaré (Brazil). Mesozooplankton (> 300 μm) was collected during nocturnal ebb tides at new moon, using three different devices to sample at three different environments: a standard ring net that was towed at subsurface, the Channel Midwater Neuston Net that collected at midwater in channels between patch reefs and the Reef Edge Net that captured organisms that are washed by ebb currents from reef tops toward the reef edge. Samples were analyzed using a ZooScan to obtain abundances and biovolume of each taxonomic group. Specific biomass measurements were taken to obtain allometric equations used to calculate zooplankton biomass from biovolume. The mesozooplankton were significantly more abundant at subsurface and at the reef edge compared to channel environments. The high abundance of organisms at reef edges suggests a low predation pressure on zooplankton at near-bottom areas, since the reefs of Tamandaré present a low coverage of planktivorous corals, being dominated by macroalgae. These results show that rather than sinks these ecosystems may be considered important sources of zooplankton available for planktivorous species. Regarding zooplankton composition, we found large amounts of initial stages of meroplanktonic larvae and newly hatched fish eggs, which presented consistently greater abundances compared to holoplankton and emergent benthic taxa. Decapod larvae were the most abundant group of the meroplankton, but cirripedian nauplii, stomatopod larvae, fish larvae and fish eggs were also abundant. More than 50% of the total biomass was due to meroplankton taxa, mainly composed of decapod larvae. This study indicates that the contribution of meroplankton to mesozooplankton composition and biomass off tropical reefs may have been underestimated.

In this paper we review the technologies available to make globally quantitative observations of particles in general—and plankton in particular—in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical and acoustical methods as well as analysis using particle counters, flow cytometers and quantitative imaging devices. We follow by highlighting the requirements necessary for a plankton observing system, the approach to achieve it and associated challenges. We conclude with ranked action-item recommendations for the next 10 years to move toward our vision of a holistic ocean-wide plankton observing system. Particularly, we suggest to begin with a demonstration project on a GO-SHIP line and/or a long-term observation site and expand from there, ensuring that issues associated with methods, observation tools, data analysis, quality assessment and curation are addressed early in the implementation. Global coordination is key for the success of this vision and will bring new insights on processes associated with nutrient regeneration, ocean production, fisheries and carbon sequestration.

The ocean is home to myriad small planktonic organisms that underpin the functioning of marine ecosystems. However, their spatial patterns of diversity and the underlying drivers remain poorly known, precluding projections of their responses to global changes. Here we investigate the latitudinal gradients and global predictors of plankton diversity across archaea, bacteria, eukaryotes, and major virus clades using both molecular and imaging data from Tara Oceans. We show a decline of diversity for most planktonic groups toward the poles, mainly driven by decreasing ocean temperatures. Projections into the future suggest that severe warming of the surface ocean by the end of the 21st century could lead to tropicalization of the diversity of most planktonic groups in temperate and polar regions. These changes may have multiple consequences for marine ecosystem functioning and services and are expected to be particularly significant in key areas for carbon sequestration, fisheries, and marine conservation. VIDEO ABSTRACT.

Marine snow aggregates represent heterogeneous agglomerates of dead and living organic matter. Composition is decisive for their sinking rates, and thereby for carbon flux to the deep sea. For oligotrophic oceans, information on aggregate composition is particularly sparse. To address this, the taxonomic composition of aggregates collected from the subtropical and oligotrophic Sargasso Sea (Atlantic Ocean) was characterized by 16S and 18S rRNA gene sequencing. Taxonomy assignment was aided by a collection of the contemporary plankton community consisting of 75 morphologically and genetically identified plankton specimens. The diverse rRNA gene reads of marine snow aggregates, not considering Trichodesmium puffs, were dominated by copepods (52%), cnidarians (21%), radiolarians (11%), and alveolates (8%), with sporadic contributions by cyanobacteria, suggesting a different aggregate composition than in eutrophic regions. Composition linked significantly with sampling location but not to any measured environmental parameters or plankton biomass composition. Nevertheless, indicator and network analyses identified key roles of a few rare taxa. This points to complex regulation of aggregate composition, conceivably affected by the environment and plankton characteristics. The extent to which this has implications for particle densities, and consequently for sinking rates and carbon sequestration in oligotrophic waters, needs further interrogation.

TARA-Mediterranean expedition crossed the entire Mediterranean Sea in 2014 to study the distribution and concentration of floating microplastics and zooplankton. Surface samples were collected with a 330 µm Manta net, plastics were sorted from 124 samples and digitally imaged with the ZoosCan system. Results showed that plastic fragments were present in all samples with an average of 2.6 x 105 items/km2 and values varying from 2 x 103 items/km2 in the Eastern basin, to more than 2 x 106 items/km2 in the Western basin. Coastal zones of Naples, Corsica and Marseille were clearly identified as areas of particularly high plastic concentration.

Aim: Invasive species are of increasing global concern. Nevertheless, the mechanisms driving further distribution after the initial establishment of non-native species remain largely unresolved, especially in marine systems. Ocean currents can be a major driver governing range occupancy, but this has not been accounted for in most invasion ecology studies so far. We investigate how well initial establishment areas are interconnected to later occupancy regions to test for the potential role of ocean currents driving secondary spread dynamics in order to infer invasion corridors and the source-sink dynamics of a non-native holoplanktonic biological probe species on a continental scale. Location: Western Eurasia. Time period: 1980s-2016. Major taxa studied: `Comb jelly' Mnemiopsis leidyi. Methods: Based on 12,400 geo-referenced occurrence data, we reconstruct the invasion history of M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match the temporal and spatial spread dynamics with large-scale connectivity patterns via ocean currents. Additionally, genetic markers are used to test the predicted connectivity between subpopulations. Results: Ocean currents can explain secondary spread dynamics, matching observed range expansions and the timing of first occurrence of our holoplanktonic non-native biological probe species, leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after cold winters were followed by rapid recolonizations at a speed of up to 2,000 km per season. Source areas hosting year-round populations in highly interconnected regions can re-seed genotypes over large distances after local extinctions. Main conclusions: Although the release of ballast water from container ships may contribute to the dispersal of non-native species, our results highlight the importance of ocean currents driving secondary spread dynamics. Highly interconnected areas hosting invasive species are crucial for secondary spread dynamics on a continental scale. Invasion risk assessments should consider large-scale connectivity patterns and the potential source regions of non-native marine species.

Mucous-mesh grazers (pelagic tunicates and thecosome pteropods) are common in oceanic waters and efficiently capture, consume and repackage particles many orders of magnitude smaller than themselves. They feed using an adhesive mucous mesh to capture prey particles from ambient seawater. Historically, their grazing process has been characterized as non-selective, depending only on the size of the prey particle and the pore dimensions of the mesh. The purpose of this review is to reverse this assumption by reviewing recent evidence that shows mucous-mesh feeding can be selective. We focus on large planktonic microphages as a model of selective mucus feeding because of their important roles in the ocean food web: as bac-terivores, prey for higher trophic levels, and exporters of carbon via mucous aggregates, faecal pellets and jelly-falls. We identify important functional variations in the filter mechanics and hydrodynamics of different taxa. We review evidence that shows this feeding strategy depends not only on the particle size and dimensions of the mesh pores, but also on particle shape and surface properties , filter mechanics, hydrodynamics and grazer behaviour. As many of these organisms remain critically understudied, we conclude by suggesting priorities for future research.

As jellyfish interactions with humans increase in coastal waters, there is an urgent need to provide science-based management strategies to mitigate the negative socioeconomic impacts of jellyfish blooms and to exploit potential benefits of their ecosystem services. This Theme Section presents the latest advances in jellyfish research, from new sampling methods to food-web and life-cycle studies. The methodological advances presented will help to overcome difficulties in sampling due to the fluctuations in abundance and irregular distributions of jellyfish. The ecology of gelatinous species in marine food webs is explored through studying interactions between jellyfish and fish. Aspects of jellyfish life cycles, which often include both attached polyps and swimming medusae, are elucidated by locating the polyps and determining the factors that contribute to their success. Knowledge on all of these factors will be essential to understand the bloom dynamics of specific jellyfish groups.

Collodaria (Retaria) are important contributors to planktonic communities and biogeochemical processes (e.g., the biologic pump) in oligotrophic oceans. Similarly to corals, Collodaria live in symbiosis with dinoflagellate algae, a relationship that is thought to explain partly their ecological success. In the context of global change, the robustness of the symbiotic interaction, and potential subsequent bleaching events are of primary interest for oceanic ecosystems functioning. In the present study, we compared the ultrastructure, morphology, symbiont density, photosynthetic capacities and respiration rates of colonial Collodaria exposed to a range of temperatures corresponding to natural conditions (21 • C), moderate (25 • C), and high (28 • C) thermal stress. We showed that symbiont density immediately decreased when temperature rose to 25 • C, while the overall Collodaria holobiont metabolic activity increased. When temperature reached 28 • C, the holobiont respiration nearly stopped and the host morphological structure was largely damaged, as if the host tolerance threshold has been crossed. Over the course of the experiment, the photosynthetic capacities of remaining algal symbionts were stable, chloroplasts being the last degraded organelles in the microalgae. These results contribute to a better characterization and understanding of temperature-induced bleaching processes in planktonic photosymbioses.

We assessed the influence of the marine dia-zotrophic cyanobacterium Trichodesmium on the bio-optical properties of western tropical South Pacific (WTSP) waters (18–22 • S, 160 • E–160 • W) during the February–March 2015 OUTPACE cruise. We performed measurements of backscattering and absorption coefficients, irradiance, and radiance in the euphotic zone with a Satlantic MicroPro free-fall profiler and took Underwater Vision Profiler 5 (UPV5) pictures for counting the largest Trichodesmium spp. colonies. Pigment concentrations were determined by fluorimetry and high-performance liquid chromatography and picoplankton abundance by flow cytometry. Tri-chome concentration was estimated from pigment algorithms and validated by surface visual counts. The abundance of large colonies counted by the UVP5 (maximum 7093 colonies m −3) was well correlated to the trichome concentrations (maximum 2093 trichomes L −1) with an ag-gregation factor of 600. In the Melanesian archipelago, a maximum of 4715 trichomes L −1 was enumerated in pump samples (3.2 m) at 20 • S, 167 30 • E. High Trichodesmium abundance was always associated with absorption peaks of mycosporine-like amino acids (330, 360 nm) and high particulate backscattering, but not with high Chl a fluorescence or blue particulate absorption (440 nm). Along the west-to-east transect, Trichodesmium together with Prochlorococ-cus represented the major part of total chlorophyll concentration ; the contribution of other groups were relatively small or negligible. The Trichodesmium contribution to total chlorophyll concentration was the highest in the Melane-sian archipelago around New Caledonia and Vanuatu (60 %), progressively decreased to the vicinity of the islands of Fiji (30 %), and reached a minimum in the South Pacific Gyre where Prochlorococcus dominated chlorophyll concentration. The contribution of Trichodesmium to zeaxanthin was respectively 50, 40 and 20 % for these regions. During the OUTPACE cruise, the relationship between normalized water-leaving radiance (nL w) in the ultraviolet and visible and chlorophyll concentration was similar to that found during the BIOSOPE cruise in the eastern tropical Pacific. Principal component analysis (PCA) of OUTPACE data showed that nL w at 305, 325, 340, 380, 412 and 440 nm was strongly correlated to chlorophyll and zeaxanthin, while nL w at 490 Published by Copernicus Publications on behalf of the European Geosciences Union. 5250 C. Dupouy et al.: Trichodesmium impact on UV–Vis radiance and pigments and 565 nm exhibited lower correlations. These results, as well as differences in the PCA of BIOSOPE data, indicated that nL w variability in the greenish blue and yellowish green during OUTPACE was influenced by other variables associated with Trichodesmium presence, such as backscattering coefficient, phycoerythrin fluorescence and/or zeaxanthin absorption , suggesting that Trichodesmium detection should involve examination of nL w in this spectral domain.

Plankton was sampled with various nets, from bottom or 500m depth to the surface, in many oceans of the world. Samples were imaged with a ZooScan. The full images were processed with ZooProcess which generated regions of interest (ROIs) around each individual object and a set of associated features measured on the object (see Gorsky et al 2010 for more information). The same objects were re-processed to compute features with the scikit-image toolbox (http://scikit-image.org). The 1,433,278 resulting objects were sorted by a limited number of operators, following a common taxonomic guide, into 93 taxa, using the web application EcoTaxa (http://ecotaxa.obs-vlfr.fr). The archive contains: taxa.csv.gz Table of the classification of each object in the dataset, with columns - objid: unique object identifier in EcoTaxa (integer number). - taxon: taxonomic name. Ambiguous names are made unique by including the name of the parent taxon in parentheses, after the name of the taxon. - lineage: full taxonomic lineage corresponding to this taxon. features_native.csv.gz Table of morphological features computed by ZooProcess. All features are computed on the object only, not the background. All area/length measures are in pixels. All grey levels are in encoded in 8 bits (0=black, 255=white). With columns - objid: same as above - area: area - mean: mean grey - stddev: standard deviation of greys - mode: modal grey - min: minimum grey - max: maximum grey - perim.: perimeter - width,height dimensions - major,minor: length of major,minor axis of the best fitting ellipse - circ.: circularity: 4pi(area/perim.^2) - feret: maximal feret diameter - intden: integrated density: mean*area - median: median grey - skew,kurt: skewness,kurtosis of the histogram of greys - %area: proportion of the image corresponding to the object - area_exc: area excluding holes - fractal: fractal dimension of the perimeter - skelarea: area of the one-pixel wide skeleton of the image - slope: slope of the cumulated histogram of greys - histcum1,2,3: grey level at quantiles 0.25, 0.5, 0.75 of the histogram of greys - nb1,2,3: number of objects after thresholding at the grey levels above - symetrieh,symetriev: index of horizontal,vertical symmetry - symetriehc,symetrievc: same but after thresholding at level histcum1 - convperim,convarea: perimeter,area of the convex hull of the object - fcons: contrast - thickr: thickness ratio: maximum thickness/mean thickness - elongation: elongation index: major/minor - range: range of greys: max-min - meanpos: relative position of the mean grey: (max-mean)/range - cv: coefficient of variation of greys: 100*(stddev/mean) - sr: index of variation of greys: 100*(stddev/range) - perimferet: index of the relative complexity of the perimeter: perim/feret - perimmajor: index of the relative complexity of the perimeter: perim/major features_skimage.csv.gz Table of morphological features recomputed with skimage.measure.regionprops on the ROIs produced by ZooProcess. See http://scikit-image.org/docs/dev/api/skimage.measure.html#skimage.measure.regionprops for documentation. inventory.txt Tree view of the taxonomy and number of images in each taxon, displayed as text. map.png Map of the sampling locations, to give an idea of the diversity sampled in this dataset. imgs Directory containing images of each object, named according to the object id objid and sorted in subdirectories according to their taxon.

The European and American eels spawn in the subtropical convergence zone (STCZ) in the Sargasso Sea, a dynamic and relatively productive area that is strongly influenced by front and eddy formations and subducted high-saline water masses. To understand how the physical and biological environments may affect the early life history of eels, we conducted a detailed bio-physical investigation of the water column at a site of high eel larvae abundance. Diel measurements and sampling in the upper 300 m revealed strong variations in hydrographic conditions and mean depths of different taxonomic groups; however, characteristics patterns of distribution were apparent. Most species showed diel vertical migrations, ascending about 20-30 m at night, whereas examples of night-time downward migration were also seen. European eel larvae were among the species showing more extensive diel vertical migration: their population mean depth changed from 160 m at day to 100 m at night where abundance peaked at 45 m depth. Distribution and migration of eel larvae corresponded to patterns observed for small hydrozoans, supporting a proposed predator-prey linkage. The study demonstrates the diverse and vertically strongly structured plankton community of STCZ where larvae of eel and other fish find a wide range of potential niches.

Abstract Collodaria (Radiolaria) are important contributors to planktonic communities and biogeochemical processes ( e.g. the biologic pump) in oligotrophic oceans. Similarly to corals, Collodaria live in symbiosis with dinoflagellate algae, a relationship that is thought to explain partly their ecological success. In the context of global change, the robustness of the symbiotic interaction and potential subsequent bleaching events are worth consideration. In the present study, we compared the ultrastructure morphology, symbiont density, photosynthetic capacities and respiration rates of colonial Collodaria exposed to a range of temperatures corresponding to natural conditions (21°C), moderate (25°C) and high (28°C) thermal stress. We showed that symbiont density immediately decreased when temperature rises to 25°C and the collodaria holobiont metabolic activity increased. When temperature reached 28°C, the collodarian host arrived at a tolerance threshold with a respiration nearly stopped and largely damaged morphological structures. Over the course of the experiment the photosynthetic capacities of remaining symbionts were stable, chloroplasts being the last degraded organelles from the microalgae. These results contribute to a better characterization and understanding of temperature-induced bleaching processes in planktonic photosymbiosis.

Le plancton est à la base de la chaine trophique pélagique océaniques et est égalementun des acteurs principaux des flux de matière. Le plancton comporte une grande diversitétaxonomique, trophique, écophysiologique et de préférences environnementales. Leplancton subit donc directement des changements environnementaux et y répondentrapidement. Ces particularités font donc du plancton une très bonne sentinelle pour traquerles changements de l’environnement et comprendre leurs effets sur les modifications del’écosystème.Mes travaux de recherche se sont focalisés sur (1) l’étude des réponses physiologiquesde différents types de zooplancton en fonction de leur environnement ou sur (2) l’effet del’environnement sur les changements spatiaux et temporels du zooplancton, que ce soit àl’échelle spécifique ou à celle des communautés.Mes projets de recherche intègrent mes connaissances sur le plancton en général etleur écophysiologie, mais s’orientent vers l’étude du plancton de manière plus générale àtravers différentes méthodes d’analyses d’imageries quantitative, en cherchant denouvelles méthodes d’exploitation permettant potentiellement d’en exploiter les résultatsde manière plus holistique et de les lier à des informations taxonomique, trophique,génomique et écophysiologique pour étudier le plancton d’une manière moins descriptive,mais plus tourné vers l’écologie trophique, fonctionnelle et biogéochimique

During the SESAME EU FP6 project, all available particulate organic carbon (POC) data collected from drifting sediment trap and Underwater Vision Profiler deployments (INSU PROOF database, 1991–2011) were gathered in order to assess carbon export at the scale of the Mediterranean Sea. In this study, we observed that particle size, POC export, and the contribution of microphytoplankton to the phytoplankton community structure, all decreased following the west to east net primary production gradient. One the other hand, no clear longitudinal gradient was found regarding particle composition (C/N ratio or lipid content). The above longitudinal patterns were also observed at the seasonal scale from spring to summer in the northwestern subbasin. These observations suggest that particle size rather than organic matter composition controls fluxes of POC in the Mediterranean Sea. The comparison between POC and dissolved organic carbon (DOC) fluxes highlights the different time-scale of physicals vertical mechanisms and suggests that DOC flux can play an underestimated role in the supply of fresh carbon to the deep waters Mediterranean Sea. Indeed, DOC supply to deeper layers can be one order of magnitude larger than particle carbon flux but occurs in pulses when stratification breaks due to (i) deep-water formation, or (ii) winter mixing. In contrast, the vertical export of POC occurs throughout the year bringing weak, but almost continuous, energy to meso- and bathypelagic organisms.

Planktonic Foraminifera are a major contributor to the deep carbonate flux and their microfossil deposits form one of the richest databases for reconstructing paleoenvironments, particularly through changes in their taxonomic and shell composition. Using an empirically based planktonic foraminifer model that incorporates three known major physiological drivers of their biogeography – temperature, food and light – we investigate (i) the global redistribution of planktonic Foraminifera under anthropogenic climate change and (ii) the alteration of the carbonate chemistry of foraminiferal habitat with ocean acidification. The present-day and future (2090–2100) 3-D distributions of Foraminifera are simulated using temperature, plankton biomass and light from an Earth system model forced with a historical and a future (IPCC A2) high CO₂ emission scenario. Foraminiferal abundance and diversity are projected to decrease in the tropics and subpolar regions and increase in the subtropics and around the poles. Temperature is the dominant control on the future change in the biogeography of Foraminifera. Yet food availability acts to either reinforce or counteract the temperature-driven changes. In the tropics and subtropics the largely temperature-driven shift to depth is enhanced by the increased concentration of phytoplankton at depth. In the higher latitudes the food-driven response partly offsets the temperature-driven reduction both in the subsurface and across large geographical regions. The large-scale rearrangements in foraminiferal abundance and the reduction in the carbonate ion concentrations in the habitat range of planktonic foraminifers – from 10–30 μmol kg−1 in their polar and subpolar habitats to 30–70 μmol kg−1 in their subtropical and tropical habitats – would be expected to lead to changes in the marine carbonate flux. High-latitude species are most vulnerable to anthropogenic change: their abundance and available habitat decrease and up to 10% of the volume of their habitat drops below the calcite saturation horizon.

Gelatinous zooplankton are increasingly being included within ecosystem models. However, for the majority of species, their respiratory and excretory processes are poorly understood, making accurate model predictions difficult. Fragility and a broad size range have resulted in a number of methods being used for different species, some in situ and others under laboratory conditions. This makes it difficult to compare studies and incorporate the data into models. Oxygen optodes have been used here to obtain respiration rates of seven species (n = 65 individuals), utilising the same method across a large range of incubator sizes (252 mL to 31.25 L) and specimen masses (< 1-2560 g wet mass). These data add respiration rates over a wider mass range to five gelatinous genera - Cestum, Geryonia, Rhizostoma, Mnemiopsis, Solmissus and provide the first respiration rate of the fragile ctenophore Leucothea multicornis. In situ data are compared with laboratory rates and trends developed for several species by adding to previously published work. Finally these data do not significantly elevate the allometric slope of a gelatinous zooplanlcton carbon mass: respiration rate (b = 0.795) relationship, despite increasing both the mass range and sample size.

Background : Simple life cycles arise from complex life cycles when one or more developmental stages are lost. This raises a fundamental question - how can an intermediate stage, such as a larva, be removed, and development still produce a normal adult? To address this question, we examined the development in several species of pelagiid jellyfish. Most members of Pelagiidae have a complex life cycle with a sessile polyp that gives rise to ephyrae (juvenile medusae); but one species within Pelagiidae, Pelagia noctiluca, spends its whole life in the water column, developing from a larva directly into an ephyra. In many complex life cycles, adult features develop from cell populations that remain quiescent in larvae, and this is known as life cycle compartmentalization and may facilitate the evolution of direct life cycles. A second type of metamorphic processes, known as remodeling, occurs when adult features are formed through modification of already differentiated larval structures. We examined muscle morphology to determine which of these alternatives may be present in Pelagiidae. Results : We first examined the structure and development of polyp and ephyra musculature in Chrysaora quinquecirrha, a close relative of P. noctiluca with a complex life cycle. Using phallotoxin staining and confocal microscopy, we verified that polyps have four to six cord muscles that persist in strobilae and discovered that cord muscles is physically separated from ephyra muscle. When cord muscle is removed from ephyra segments, normal ephyra muscle still develops. This suggests that polyp cord muscle is not necessary for ephyra muscle formation. We also found no evidence of polyp-like muscle in P. noctiluca. In both species, we discovered that ephyra muscle arises de novo in a similar manner, regardless of the life cycle. Conclusions : The separate origins of polyp and ephyra muscle in C. quinquecirrha and the absence of polyp-like muscle in P. noctiluca suggest that polyp muscle is not remodeled to form ephyra muscle in Pelagiidae. Life cycle stages in Scyphozoa may instead be compartmentalized. Because polyp muscle is not directly remodeled, this may have facilitated the loss of the polyp stage in the evolution of P. noctiluca.

The economic and societal impacts of nano-materials are enormous. However, releasing such materials in the environment could be detrimental to human health and the ecological biosphere. Here we demonstrate that gold and quantum dots nanoparticles bio-accumulate into mucus materials coming from natural species such as jellyfish. One strategy that emerges from this finding would be to take advantage of these trapping properties to remove nanoparticles from contaminated water.

Copepods are the optimal live feed for hatcheries and improvement of cultivation techniques, to provide a constant food source, is crucial for the expansion of the industry. However, studies based on experimental work and real observations can be labour intensive and expensive. A simple model was developed based on the well-known life history traits of Acartia tonsa to describe batch cultures and their productivity. Model results were compared to observations from real cultures. For maximizing egg production yields, the optimal stocking density of copepods should be adapted to the design (depth) of the culture tanks. At high densities, stress due to encountering conspecifics, as well as cannibalism of eggs by adults, limits egg production yields. Using this model, the potential selection efficacy of copepod strains was also evaluated in order to increase production yields. Selecting larger copepods increases the egg production per litre of culture, but decreases the optimal stocking density and the range of densities at which egg production yield is high, and vice-versa. Selecting copepods that are less affected by stress due to conspecifics only affect production yields at very high adult densities. However, selecting copepods with a high Specific Growth Rate (SGR), or improving their SGR, was found to be an alternative which did not affect the optimal cultivation densities but improved egg production yields.

Four cohorts of the scyphozoan jellyfish Pelagia noctiluca were grown in the laboratory. For the first time, P. noctiluca was grown from eggs through to reproductive adults. The maximum life span in the laboratory was 17 mo. Pelagia noctiluca were first observed to release gametes at an umbrella diameter of 2.4 cm. Laboratory growth under steady feeding conditions showed initial growth followed by stagnation until dietary conditions were altered. A mismatch between the availability of optimal food and the presence of developmental stages may significantly increase the mortality rates of the young stages. Non-motile prey improved survival of ephyrae stages compared with zooplankton, but good survival and ephyrae growth were only obtained with a high-energy sea urchin egg diet. Maximal growth rates were up to 30% d(-1) for young ephyrae and 1.5-4% d(-1) for adults. Maximal growth rates were comparable between laboratory and in situ growth observations in the Ligurian Sea during 1969 and 2013. Combining observations would suggest that 230 d of continuous growth are required to reach the largest mean size observed in the wild (June 2013, mean +/- SD = 15.6 +/- 2.8 cm, range = 12-21 cm). We suggest that 90-120 d of continuous growth from planula larvae would yield reproductive individuals under ideal growing conditions. We discuss the daily prey abundances required by each individual to sustain basal metabolism and the observed growth rates.

The holoplanktonic jellyfish Pelagia noctiluca is renowned for periods of high abundance, causing considerable problems to tourism and aquaculture. Little is understood about the drivers of its periodic presence and absence or how it survives unfavourable periods. Studying the effect of starvation, we evaluated the main metabolic expenses (reproduction, respiration and excretion) during those periods. P. noctiluca could shrink in size, losing up to 85% of their mass (6.6-7.1% loss day(-1)), while continuing to release eggs quasi-daily over a 28-day period. Egg production was proportional to size (mean 759 eggs day(-1) at 6 cm bell diameter), with up to 19 526 eggs released in a single spawn, thereby providing huge potential for population growth despite undergoing starvation. Small food rations decreased the rate of shrinking to 3.1% day(-1), prolonging life (49 days), potentially enhancing the chances of encountering more prey and regrowing. Metabolism increased with wet mass (allometric exponent: 0.93 for respiration, 0.82 for ammonium), however reproduction was the greatest carbon expenditure for individuals larger than 9 cm bell diameter. Temperature (9-29 degrees C) also significantly increased both respiration and, to a greater extent, excretion (Q(10) = 2.25 and 4.76). Consequentially a warming ocean may negatively affect survival rates unless prey abundance balances the increased metabolic demands.

Oxygen optodes were used to compare respiration rates of newly caught and laboratory-incubated Mnemiopsis leidyi ctenophores. No significant difference was found between the treatments. Overall, the respiration rate was significantly correlated with temperature (8.5-30A degrees C) and organism weight (0.41-19.4 g wet weight, 6-42 mm oral-aboral length), together explaining 87% of the variation. Greater individual variation was observed > 25A degrees C. Q(10) measured at near-ambient temperatures (2.49) and over the entire range (2.57) was lower than or comparable with previous estimates for this species. Mnemiopsis leidyi from a French lagoon have the metabolic capacity to survive year round in the ambient temperature range of the western Mediterranean.

The climates of the mid-Holocene (MH), 6,000 years ago, and of the Last Glacial Maximum (LGM), 21,000 years ago, have extensively been simulated, in particular in the framework of the Palaeoclimate Modelling Intercomparison Project. These periods are well documented by paleo-records, which can be used for evaluating model results for climates different from the present one. Here, we present new simulations of the MH and the LGM climates obtained with the IPSL_CM5A model and compare them to our previous results obtained with the IPSL_CM4 model. Compared to IPSL_CM4, IPSL_CM5A includes two new features: the interactive representation of the plant phenology and marine biogeochemistry. But one of the most important differences between these models is the latitudinal resolution and vertical domain of their atmospheric component, which have been improved in IPSL_CM5A and results in a better representation of the mid-latitude jet-streams. The Asian monsoon's representation is also substantially improved. The global average mean annual temperature simulated for the pre-industrial (PI) period is colder in IPSL_CM5A than in IPSL_CM4 but their climate sensitivity to a CO₂ doubling is similar. Here we show that these differences in the simulated PI climate have an impact on the simulated MH and LGM climatic anomalies. The larger cooling response to LGM boundary conditions in IPSL_CM5A appears to be mainly due to differences between the PMIP3 and PMIP2 boundary conditions, as shown by a short wave radiative forcing/feedback analysis based on a simplified perturbation method. It is found that the sensitivity computed from the LGM climate is lower than that computed from 2 × CO₂ simulations, confirming previous studies based on different models. For the MH, the Asian monsoon, stronger in the IPSL_CM5A PI simulation, is also more sensitive to the insolation changes. The African monsoon is also further amplified in IPSL_CM5A due to the impact of the interactive phenology. Finally the changes in variability for both models and for MH and LGM are presented taking the example of the El-Niño Southern Oscillation (ENSO), which is very different in the PI simulations. ENSO variability is damped in both model versions at the MH, whereas inconsistent responses are found between the two versions for the LGM. Part 2 of this paper examines whether these differences between IPSL_CM4 and IPSL_CM5A can be distinguished when comparing those results to palaeo-climatic reconstructions and investigates new approaches for model-data comparisons made possible by the inclusion of new components in IPSL_CM5A.

Copepods are major consumers of sinking marine particles and hence reduce the efficiency of the biological carbon pump. Their high abundance on marine snow suggests that they can detect sinking particles remotely. By means of laboratory observations, we show that the copepod Temora longicornis can detect chemical trails originating from sinking marine snow particles (appendicularian houses). The chemical cue was detected by copepods from a distance of >25 particle radii, with the probability of detection decreasing with distance. The behavior of T. longicornis following the trail resembled the behavior of males tracking pheromone trails, although with a lower tracking velocity. Upon finding a house, the copepod would attach for a short period (10-30 s) and feed intensively. Due to short residence times, daily feeding rates were moderate. Our results demonstrate that even T. longicornis, a species usually considered a microparticle feeder, is able to detect and feed on marine snow aggregates. If similar behaviors are displayed by the more dedicated aggregate-feeding copepods, a topic that remains unexplored, the effect of copepods on vertical flux attenuation may be significant.

The climates of the mid-Holocene (MH, 6,000 years ago) and the Last Glacial Maximum (LGM, 21,000 years ago) have been extensively documented and as such, have become targets for the evaluation of climate models for climate contexts very different from the present. In Part 1 of the present work, we have studied the MH and LGM simulations performed with the last two versions of the IPSL model: IPSL_CM4, run for the PMIP2/CMIP3 (Coupled Model Intercomparison Project) projects and IPSL_CM5A, run for the most recent PMIP3/CMIP5 projects. We have shown that not only are these models different in their simulations of the PI climate, but also in their simulations of the climatic anomalies for the MH and LGM. In the Part 2 of this paper, we first examine whether palaeo-data can help discriminate between the model performances. This is indeed the case for the African monsoon for the MH or for North America south of the Laurentide ice sheet, the South Atlantic or the southern Indian ocean for the LGM. For the LGM, off-line vegetation modelling appears to offer good opportunities to distinguish climate model results because glacial vegetation proves to be very sensitive to even small differences in LGM climate. For other cases such as the LGM North Atlantic or the LGM equatorial Pacific, the large uncertainty on the SST reconstructions, prevents model discrimination. We have examined the use of other proxy-data for model evaluation, which has become possible with the inclusion of the biogeochemistry morel PISCES in the IPSL_CM5A model. We show a broad agreement of the LGM-PI export production changes with reconstructions. These changes are related to the mixed layer depth in most regions and to sea-ice variations in the high latitudes. We have also modelled foraminifer abundances with the FORAMCLIM model and shown that the changes in foraminifer abundance in the equatorial Pacific are mainly forced by changes in SSTs, hence confirming the SST-foraminifer abundance relationship. Yet, this is not the case in all regions in the North Atlantic, where food availability can have a strong impact of foraminifer abundances. Further work will be needed to exhaustively examine the role of factors other than climate in piloting changes in palaeo-indicators.

Recently, both the invasive ctenophore Mnemiopsis leidyi and the arctic Mertensia ovum were discovered in the Baltic Sea but their range expansion remains unclear due to misidentification of their larval stages. Supported by molecular species verification we describe seasonal abundance and distribution of larvae and eggs of these two species. We show that their occurrence is significantly but inversely related to salinity. Mertensia ovum was present year round throughout the brackish Baltic Sea but also occurred in high-saline areas during cold seasons. Larvae of M. leidyi occurred throughout all seasons in high-saline areas but never extended further into the central Baltic. Highest ctenophore egg abundances were observed in high-saline areas during summer along with the first appearance of M. leidyi adults. The M. leidyi population peaked 2 months after the first occurrence of adults in high-saline areas, suggesting these areas as a source for lower saline regions. Low larvae abundances and a reduced transitional-to-adult ratio in the southern Baltic point to reduced or no active recruitment, suggesting that drift of animals from high-saline into lower saline regions sustains the M. leidyi population in the southern Baltic such as the Arkona and Bornholm basins.

Ballast material (organic, opal, calcite, lithogenic) is suggested to affect sinking speed of aggregates in the ocean. Here, we tested this hypothesis by incubating appendicularians in suspensions of different algae or Saharan dust, and observing the sinking speed of the marine snow formed by their discarded houses. We show that calcite increases the sinking speeds of aggregates by ~100% and lithogenic material by ~150% while opal only has a minor effect. Furthermore the effect of ballast particle concentration was causing a 33 m d-1 increase in sinking speed for a 5×10 5 µm 3 ml-1 increase in particle concentration, near independent on ballast type. We finally compare our observations to the literature and stress the need to generate aggregates similar to those in nature in order to get realistic estimates of the impact of ballast particles on sinking speeds.

The scyphozoan Pelagia noctiluca reproduces by direct development without a benthic stage. Typically, this jellyfish is found offshore with a holoplanktonic lifecycle, vertical migration and feeding behaviours. Frequent outbreaks have been well documented on the Mediterranean shores since the 19th century; however, the offshore distribution of this species remains mostly unknown. In this study, we performed a bimonthly monitoring of P. noctiluca surface density, at high resolution, from a sailboat, along a 35-km coastal to offshore transect in the Ligurian Sea, between February and October 2011. During daylight, P. noctiluca was rarely seen. At night, offshore, P. noctiluca was always present, while within 5 km of the coast, P. noctiluca was rarely observed. Pelagia noctiluca aggregations were most abundant within the Northern Current of the Ligurian Sea. Our findings suggest that P. noctiluca outbreaks observed on Mediterranean shores may result from the transport of the permanent offshore population inshore by specific hydrodynamic conditions.

The relative abundance of Globigerinoides bul-loides was used to infer Holocene paleo-productivity changes on the Oman margin and at the southern tip of India. Today , the primary productivity at both sites reaches its maximum during the summer season, when monsoon winds result in local Eckman pumping, which brings more nutrients to the surface. On a millennium timescale , however, the % G. bulloides records indicate an opposite evolution of paleo-productivity at these sites through the Holocene. The Oman Margin productivity was maximal at ∼9 ka (boreal summer insolation maximum) and has decreased since then, suggesting a direct response to insolation forcing. On the contrary, the productivity at the southern tip of India was minimum at ∼9 ka, and strengthened towards the present. Paleo-reconstructions of wind patterns, marine productivity and foraminifera assemblages were obtained using the IPSL-CM4 climate model coupled to the PISCES marine biogeochemical model and the FORAMCLIM ecophysiolog-ical model. These reconstructions are fully coherent with the marine core data. They confirm that the evolution of particulate export production and foraminifera assemblages at our two sites were directly linked with the strength of the up-welling. Model simulations at 9 ka and 6 ka BP show that the relative evolution between the two sites since the early Holocene can be explained by the weakening but also the southward shift of monsoon winds over the Arabian Sea during boreal summer.

We present an eco-physiological model reproducing the growth of eight foraminifer species (Neogloboquad-rina pachyderma, Neogloboquadrina incompta, Neoglobo-quadrina dutertrei, Globigerina bulloides, Globigeri-noides ruber, Globigerinoides sacculifer, Globigerinella si-phonifera and Orbulina universa). By using the main physiological rates of foraminifers (nutrition, respiration, symbi-otic photosynthesis), this model estimates their growth as a function of temperature, light availability, and food concentration. Model parameters are directly derived or calibrated from experimental observations and only the influence of food concentration (estimated via Chlorophyll-a concentration) was calibrated against field observations. Growth rates estimated from the model show positive correlation with observed abundance from plankton net data suggesting close coupling between individual growth and population abundance. This observation was used to directly estimate potential abundance from the model-derived growth. Using satellite data, the model simulate the dominant foraminifer species with a 70.5% efficiency when compared to a data set of 576 field observations worldwide. Using outputs of a biogeochemical model of the global ocean (PISCES) instead of satellite images as forcing variables gives also good results, but with lower efficiency (58.9%). Compared to core tops observations, the model also correctly reproduces the relative worldwide abundance and the diversity of the eight species when using either satellite data either PISCES results. This model allows prediction of the season and water depth at which each species has its maximum abundance potential. This offers promising perspectives for both an improved quantification of paleoceanographic reconstructions and for a better understanding of the foraminiferal role in the marine carbon cycle.

So far, appendicularians role in the biogeochemical cycling of organic matter has been overlooked. Appendicularians represent only a fraction of total mesozooplankton biomass, however these ubiquitous zooplankters have very high filtration and growth rates compared to copepod, and produce numerous fecal pellets and filtering houses contributing to the export production by aggregating small marine particles. To study their quantitative impact on biogeochemical fluxes, we have included this group in the Biogeochemical Flux Model (BFM), using a recently developed ecophysiological model. One dimensional annual simulations of the pelagic ecosystem including appendicularians were conducted with realistic surface forcing for year 2000, using data from the DyFAMed open ocean station. The appendicularian grazing impact was generally low, but appendicularians increased detritus production by 8% and export production by 55% compared to a simulation without appendicularians. Therefore present biogeochemical models lacking appendicularians probably under, or misestimate the detritus and export production by omitting the pathway from small sized plankton to fast sinking detritus. Detritus production and export rates are 60% lower than estimates from mesotrophic sites, showing that appendicularians' role is lower but still significant in oligotrophic environments. The simulated annual export at 200 m exceeds sediment trap values by 44%, suggesting an intense degradation during the sinking of appendicularian detritus, supported by observations made in other sites. Thus degradation and grazing of appendicularians detritus need a better quantification if we are to accurately assess the appendicularian role in the export flux.

The effect of carbonate ion concentration ([CO 2− 3 ]) on calcification rates estimated from shell size and weight was investigated in the planktonic foraminifera Orbulina universa and Globigerinoides sacculifer. Experiments on G. sacculifer were conducted under two irradiance levels (35 and 335 µmol photons m −2 s −1). Calcification was ca. 30% lower under low light than under high light, irrespective of the [CO 2− 3 ]. Both O. universa and G. sacculifer exhibited reduced final shell weight and calcification rate under low [CO 2− 3 ]. For the [CO 2− 3 ] expected at the end of the century, the calcification rates of these two species are projected to be 6 to 13% lower than the present conditions, while the final shell weights are reduced by 20 to 27% for O. universa and by 4 to 6% for G. sacculifer. These results indicate that ocean acidification would impact on calcite production by foraminifera and may decrease the calcite flux contribution from these organisms.

Coupled-climate carbon cycle models (C4Ms) are linked to an eco-physiological model to determine the impact of climate-change and ocean acidification on the global 3D distribution of the most abundant foramifera species up until the end of this century. The eco-physiological model is used to estimate the growth-rate and abundance of eight distinct species of foramifera in response to temperature, light (for species with symbiotic algae), and food availability simulated by the four C4Ms. The models are forced using historical anthropogenic emissions and the high-emission IPPC AR4 scenario and all simulate a 2 to 20% reduction in global marine productivity and export production by 2100. In the first part of the study we present the change in both the distribution of the dominant species and their relative abundance in response to climate-change. In the second part, we additionally consider the influence of regional changes to the carbonate chemistry of seawater on the calcification rates of selected foramifera species, which allows us to also estimate the impact of ocean acidification on their biogeography.

Respiration and photosynthesis of the planktonic foraminifera Globigerinoides ruber, Orbulina universa, and Globigerinella siphonifera and their symbiotic algae were calculated from measured dissolved oxygen gradients using microelectrodes, using different temperatures in dark and light (250 mmol photon m$^{-2} s^{-12}$ conditions. At one temperature (24°C) the respiration rate increased as a power function of the foraminiferan organic carbon mass with a 0.57 $\pm$ 0.18 exponent. The effect of temperature on respiration was quantified in two ways: by normalizing the rates to the organic carbon mass and by normalizing the observed rates to a constant temperature (24°C). This latter normalization was also used for photosynthesis. The respiration rates increase as a function of temperature for all species and can be described either with a $Q_{10}$ = 3.18 ($\pm$0.27) or with an Arrhenius temperature of $T_A$ = 10,293°K ($\pm$768°K). Similar calculations for net photosynthesis yielded a $Q_{10}$ 2.68 ($\pm$0.36) and a $T_A$ = 8766°K ($\pm$1203°K), and calculations for gross photosynthesis yielded a $Q_{10}$= 2.76 ($\pm$0.29) and a $T_A$ = 9026°K ($\pm$926°K). For the species studied, the photosynthesis : respiration ratio varied from moderate for $G.\ siphonifera$ (0.58) to very high (13) for $O.\ universa$. The high ratios indicate that photosynthesis is much higher than the carbon requirements for both foraminifera and symbiont growth. This excess carbon might be the source of organic exudates

Mesopelagic gelatinous zooplankton fauna are insufficiently known because of inappropriate and infrequent sampling, but may have important trophic roles. In situ imaging systems and undersea vehicles have been used to investigate their diversity, distribution, and abundance. The use of different platforms, however, restricts the comparison of data from different regions. Starting in 2001, the underwater video profiler (UVP) was deployed during 12 cruises in six oceanic regimes (Mediterranean Sea, North Atlantic shelves, Mid-Atlantic Ridge, tropical Pacific Ocean, eastern Indian Ocean, and Subantarctic Ocean) to determine the vertical distribution of organisms in the upper 1000 m. Nine oceanic regions were identified based on the hydrological properties of the water column. They correspond to nine of the biogeochemical provinces defined by Longhurst. In all, 21 morphotypes were recognized: sarcodines (eight groups), ctenophores (two groups), siphonophores, medusae (five groups), crustaceans (one group), chaetognaths, appenclicularians, salps, and fish. The similarity in the community assemblages of zooplankton in the 100-1000 m layer was significantly greater within regions than between regions, in most cases. The regions with comparable composition were located in the North Atlantic with adjacent water masses, suggesting that the assemblages were either mixed by advective transport or that environmental conditions were similar in mesopelagic layers. The data suggest that the spatial structuring of mesopelagic macrozooplankton occurs on large scales (e.g. basin scales) but not necessarily on smaller scales (e.g. oceanic front).