The marine biogeochemical cycling of trace elements (TEs) at ocean margins is still poorly understood. Unravelling TE sources and exploring their exchange between the coastal environment and the open ocean remain poorly explored. Here, we examined the dissolved Co, Ni, Cu, Zn, and Pb concentration distributions in the waters of the northern part of the Western Mediterranean (WMED), namely the continental shelf of the Gulf of Lion (GoL) and the North Gyre (NG). In GoL waters, median values (with interquartile ranges, IQR) were 135 pM (110–463 pM) for Co, 3.94 nM (3.73–4.52 nM) for Ni, 2.70 nM (2.31–3.73 nM) for Cu, 4.73 nM (3.60–6.44 nM) for Zn, and 117 pM (102–161 pM) for Pb. In NG waters, they were 37 pM (35–46 pM) for Co, 4.60 nM (4.52–4.65 nM) for Ni, 1.79 nM (1.77–1.85 nM) for Cu, 5.43 nM (5.05–5.95 nM) for Zn, and 94 pM (92–98 pM) for Pb. Our results show that in the GoL, Co, Ni, Cu, and, to a lesser extent, Zn, are negatively correlated with salinity, indicating significant riverine inputs. In the NG, Ni presents a nutrient-like behavior, whereas other TEs are still enriched in upper waters. Zn and Pb distributions suggest the influence of atmospheric deposition with substantial human imprints. The estimated TE transfers in this system disclose the importance of dense water formation in the export of TEs from the continent to the offshore deep waters of the WMED.

Les céphalopodes d’une manière générale et les spécimens de grande taille précisément, ont depuis l’Antiquité occupé une place majeure dans l’imaginaire des hommes ; les récits de marins décrivant des monstres effrayants capables de faire sombrer un navire sont innombrables. Il n’est pas facile de faire la part du réel dans ces témoignages souvent fantasmés, surtout que les animaux dont il est question vivent généralement à de grandes profondeurs et, pendant très longtemps, seuls les spécimens échoués, souvent en mauvais état, étaient étudiés. Ainsi, il n’est pas surprenant que la littérature et le cinéma se soient emparés de ces créatures spectaculaires. Encore aujourd’hui, ces animaux des abysses sont relativement peu connus.

Jusqu’à l’expédition du Challenger (1872-1876), et en dépit de travaux isolés qui démontrèrent le contraire dès le début du XIXème siècle, la communauté naturaliste était convaincue que les profondeurs marines n’abritaient aucune vie animale. Mais dès que les découvertes du Challenger furent publiées, les zoologistes prirent connaissance de formes de vie tout à fait inédites et les artistes qui représentaient à cette époque les organismes étudiés par les scientifiques permirent aux spécialistes mais aussi à un public plus large de visualiser des créatures surprenantes. D’autres expéditions, notamment celle du Valdivia (1898-1899), révélèrent une vie abyssale toujours plus diverse et abondante, lithographiée ou aquarellée jusqu’au milieu du XXème siècle, avant que la photographie n’ouvre une autre perspective artistique.

Dans une région encore très pauvre et dénuée d’infrastructures jusqu’à la fin du XVIIIe siècle, la naissance et le développement de la Station zoologique de Villefranche-sur-Mer, aujourd’hui sous la tutelle de Sorbonne Université, n’allaient pas de soi, tandis que d’autres laboratoires émergeaient ailleurs en Europe. Son épanouissement ne fut pas non plus facile, avec bien des aléas liés à l’Histoire régionale. Le présent ouvrage tente de présenter les causes qui ont présidé à sa genèse (essor des sciences de la mer, contexte historique, spécificités de la baie de Villefranche) et d’éclaircir les péripéties qui ont abouti au centre de recherches actuel, reconnu internationalement. Le lecteur trouvera ici beaucoup de documents d’époques diverses qui l’éclaireront sur une destinée aussi mouvementée que fascinante. Les auteurs ont tous trois réalisé leur carrière à la Station Marine de Villefranche (rebaptisée en 2018 Institut de la mer de Villefranche – IMEV) et se sont très tôt intéressés à l’épopée de leur lieu de travail.

Scleractinian corals rely on symbiosis with Symbiodiniaceae, a family of marine dinoflagellates, for photosynthetic products, which sustains their growth in nutrient-poor environments. Manganese (Mn) is a critical element for photosynthesis as an essential cofactor for the oxygen-evolving complex of the photosynthetic machinery. Also, Mn is an essential metal involved in antioxidant mechanisms that maintain normal cellular function in heat stressed corals. Objectives: This study aims to investigate the effects of different Mn species on photosynthetic efficiency in the coral Stylophora pistillata under thermal stress. A Mn-alginate device for controlled Mn supplementation was developed for this purpose. Methods: Coral nubbins were exposed to the following Mn species: manganese(II) chloride (MnCl₂), manganese(II) ethylenediamine-N,N′-disuccinate (MnEDDS), manganese(II) desferrioxamine (MnDFO), and manganese(III) citrate (MnCIT). Photosynthetic parameters were measured using fluorometry. Mn-alginate gel dishes were prepared for controlled release, and their impacts on coral health indicators were evaluated at 26 °C and 31 °C, including photosynthetic efficiency, oxygen production, and symbiont density. Results: Free Mn(II) (MnCl2) and MnEDDS significantly enhanced photosynthetic efficiency. Mn-alginate effectively delivered Mn in controlled bursts. Under thermal stress, Mn supplementation improved photosynthetic activity and favored symbiont density. Mn-alginate dishes were stable in seawater and biocompatible, releasing Mn optimally at elevated temperatures. Conclusion: Mn-alginate gel dishes are an efficient and safe method for improving coral photosynthesis and mitigating thermal stress impacts, supporting reef conservation efforts in a changing climate.

Here are presented two letters by a young Ernst Haeckel, who became a major figure of biology, as well as recognized as a scientific artist, in the late 19th century. The letters, previously available only in German, are given here with his illustrations, in English. They were written when he was a medical student, addressed to his parents, describing his travels and impressions during one of his first voyages abroad. They show Haeckel with a character distinct from his latter years, somewhat insecure, eager to share his experiences with his parents. Haeckel's talent as a storyteller and travel writer were evident early on. During his stay in Nice he saw, for the first time, living specimens of organisms that would later be the subjects of iconic illustrations. In a companion article (Migon et al. 2024), the letters are presented and discussed in French.

Sont présentées ici deux lettres adressées à ses parents en 1856 du jeune Ernst Haeckel, figure majeure de la biologie à la fin du XIX ème siècle mais aussi dessinateur et aquarelliste de talent. Cette correspondance, seulement disponible en allemand jusqu'à présent, est ici proposée avec ses illustrations originales en français, conjointement à une version en anglais (Dolan et al. 2024). Ecrites alors que Haeckel était encore étudiant en médecine, ces lettres décrivent ses premiers voyages à l'étranger avec ses impressions et ses réflexions. Elles révèlent un homme encore incertain, impatient de partager ses expériences avec ses parents. Apparaît surtout un naturaliste avide de découverte, inspiré par l'observation d'organismes vivants, et aussi, dans la deuxième lettre, un jeune homme éprouvé par la perte récente d'un être cher.

Mass fluxes and trace metal (TM) fluxes were measured from samples collected in 2003 to 2005 from sediment traps deployed at 1000 m depth at the DYFAMED (DYnamique des Flux Atmosphériques en MEDiterranée) time-series station (central Ligurian Sea, 2350 m depth). A highly significant correlation is observed between all TM fluxes, whatever the nature and emission source of the TM (e.g., crustal such as Al, Fe, Co, or anthropogenic such as Zn, Cd, Pb) and the mass flux. Because these TMs originate from different emission sources, and, therefore, their atmospheric deposition to the sea surface varies with different seasonal patterns, it is suggested that fluxes of particulate organic carbon determine fluxes of TMs, and not the contrary. The seasonal sequence of the transfer of TMs to sea floor (winter convection, spring bloom and nutrient depletion of surface waters in summer and autumn) is briefly examined to highlight the concomitant temporal variability of mass and TM fluxes. This suggests that the TM downward transfer is totally controlled by the seasonal variability of biogenic carbon production, itself depending upon the intensity of winter convection. This may be a peculiarity of marine regions such as the Ligurian Sea, where hydrodynamical features (and, therefore, spring blooms) are strongly constrained by climatic and meteorological conditions (winter temperature, wind events, rain events).

Using Argo profiling floats, cruises and mooring data, we reconstructed the dissolved oxygen (O2) dynamics in the Gulf of Lion and the Ligurian Sea, with a focus on the intermediate waters. By applying the CANYON-MED neural network-based method on the large network of O2-equipped Argo floats we derived nutrients and carbonate system variables in the Gulf of Lion and the Ligurian Sea at different depths in the water column and derived trends over the 2012-2020 period. In these waters, the O2 minimum is strongly affected by the intermittent convection process, and the two areas show dissimilar responses to the mixing events. In the absence of deep convection events, the O2-depleted layer tends to spread vertically and intensify even more so in the Ligurian than in the Gulf of Lion. In both areas, over the 2012-2020 period, nutrients increase overall in deep layers, with a concomitant impact on nutrient molar ratios tending toward an increase in P-limitation. Acidification estimates derived in different layers of the water column show an overall increase in dissolved inorganic carbon and a concurrent pH decrease. These trends were strongly affected by convection events slowing down the overall acidification trend.

The characterization of particles in suspension in river plumes contributes to the assessment of net particulate organic carbon (POC) fluxes and to a better understanding of the anthropogenic and climatic impact on blue carbon. Prior to POC analysis in natural waters, inorganic carbon (in the form of carbonates) must be removed. This step is generally carried out by acid leaching. However, the presence of mineral matrices (in turbid waters) may hinder total decarbonation, which may result in biased measurements. This work checks the quality of decarbonation through the analysis of carbon stable isotope ratio (δ 13 C), considering suspended particles discharged by three rivers into coastal waters under flooding conditions. Carbonates were removed by adding variable volumes of 2N hydrochloric acid (HCl) to filters. Carbon concentrations and stable isotopic ratios were analyzed. Values of δ 13 C org (stable isotope ratio of organic carbon) allow the identification of incompletely decarbonated samples. If a small amount of detrital carbonates resists the usual decarbonation treatment, δ 13 C org can be significantly shifted towards less negative values, suggesting the need of more efficient decarbonation methods in order to improve the accuracy of organic carbon measurements. Even in the case of a high C org /C total ratio, the impact of remaining carbonates on the δ 13 C org value is strong because δ 13 C inorg is significantly different. The sensitivity of δ 13 C org measurement might therefore be used to validate POC measurements in estuarine and coastal waters.

En raison de ses caractéristiques particulières, la mer Méditerranée est souvent considérée comme un modèle de l’océan mondial. Ses dimensions réduites et sa circulation hydrologique particulière la rendent très sensible aux contraintes environnementales et climatiques qui évoluent rapidement.La Méditerranée est un site idéal pour comprendre un certain nombre de processus océanographiques clés, en particulier la mer Ligure où les conditions océaniques se trouvent à proximité des côtes, en raison de sa géologie particulière. Une station d’observation a été établie au large pour produire des séries chronologiques de données. Cet ouvrage divisé en deux volumes synthétise cet important ensemble de données et de connaissances. Il fournit des éléments clés de l’océanographie dans un monde en mutation.Ce volume 2 étudie les flux de carbone générés par l’activité planctonique ainsi que la biologie des grandes catégories d’organismes marins. Il comporte également une revue de la contamination du sous-bassin ligure, puis expose les perspectives de l’océanographie de demain.

Microbial communities on marine aggregates could be influenced by ambient water conditions; however, empirical data are scarce. In this study, we used fingerprint analysis of PCR-amplified 16S rRNA gene fragment to examine how microbial communities on aggregates change in response to different conditions of ambient water. We conducted two experiments using seawater cultures from surface waters of the lagoon and the anthropogenically influenced bay of Nouméa, New Caledonia: a transplant experiment in which the artificially produced aggregates from one station was added to ultra-filtered seawater culture of another station, and a water-flow experiment in which the artificially produced aggregates placed in the ultra-filtered seawater culture with or without water-flow. In a transplant experiment, bacterial community composition (BCC) on the bay and lagoon water aggregates were significantly different (p < 0.05, ANOSIM) at the beginning of experiment. After 11 days of incubation, BCC on the lagoon water aggregates were significantly different (p < 0.05) from transplanted communities. Transplantation effect was also observed in the bay water treatments. In a water-flow experiment, BCC on the bay and lagoon water aggregates were significantly different (p < 0.05) at the beginning of the experiment. BCC on the lagoon and bay water aggregates with and without water-flow treatments were significantly different (p < 0.05) at the end of incubation, and effect of water-flow on BCC were observed in the bay and lagoon water treatments. Our experimental studies suggest that changes in ambient water conditions potentially influence microbial communities on aggregates in the Bay of Nouméa.

The basic bacterial ecology and diversity was investigated in five running water systems of Southern New Caledonia. These running waters were characterized by potential P-limitation and high concentrations of Ni, Fe, Mn, Cr and Co. The low concentrations of dissolved organic carbon, bacterial and viral abundance, bacterial production and growth efficiency support the characterization of the running waters as oligotroph to ultraoligotroph. Despite these similarities, there were strong differences (<50% similarity) in bacterial community composition between some habitats based on 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE) fingerprints. The high coverage of sequenced DGGE bands found for Betaproteobacteria is typical for freshwater systems, however, we found also a strong representation of Gammaproteobacteria. Indeed the three bands found at all stations were related to Limnohabitans (Comamonadaceae) and Alteromonadaceae. Strong differences were also found between the free-living and the attached bacterial fraction with Gammaproteobacteria dominating in two systems. A higher representation of Gammaproteobacteria seems typical for metal-rich freshwater habitats. Consistent with fresh water habitats, majority of phylotypes detected in the sediment was affiliated to proteobacteria. Also, none of the sequences showed a 100% identity with data bases, and 10 of the 22 and 2 of the 23 sequences had similarities higher than 97% in the freshwater and sediment. This could indicate specific adaptations of the community composition either due to the high metal concentrations or due to the geographical isolation of the New Caledonia.

Due to its particular characteristics, the Mediterranean Sea is often viewed as a microcosm of the World Ocean. Its proportionallyreduced dimensions and peculiar hydrological circulation render it susceptible to environmental and climatic constraints, which are rapidly evolving. The Mediterranean is therefore an ideal site to examine, in order to better understand a number of key oceanographic phenomena. This is especially true of the Ligurian Sea where, due to its geology, oceanic conditions are found close to the coast. As such, 30 years ago, an offshore time-series site provided a fresh impetus to a long history of marine biology research, which has generated a very important body of data and knowledge. This is the first volume, in a two-volume series, that summarizes this research. Across these two books, the reader will find 13 chapters that examine the geology, physics, chemistry and biology of the Ligurian Sea ? always with the goal of providing key elements of oceanography in a changing world.

Due to its particular characteristics, the Mediterranean Sea is often viewed as a microcosm of the World Ocean. Its proportionally-reduced dimensions and peculiar hydrological circulation render it susceptible to environmental and climatic constraints, which are rapidly evolving. The Mediterranean is therefore an ideal site to examine, in order to better understand a number of key oceanographic phenomena. This is especially true of the Ligurian Sea where, due to its geology, oceanic conditions are found close to the coast. As such, 30 years ago, an offshore time-series site provided a fresh impetus to a long history of marine biology research, which has generated a very important body of data and knowledge. This is the second volume, in a two-volume series, that summarizes this research. Across these two books, the reader will find 13 chapters that examine the geology, physics, chemistry and biology of the Ligurian Sea ? always with the goal of providing key elements of oceanography in a changing world.

The barrier reef lagoon of Noumea (New Caledonia) is potentially influenced by Ni and black carbon (BC) rich aerosols (the two latter originating from a Ni power plant). Experiments were performed with lagoon water collected close to the reef crest to assess the effect of anthropogenic influences on bacterial abundance (BA), production (BP), respiration (BR), growth efficiency (BGE) and community composition (BCC) in artificial produced aggregates. In both treatments, BA and VA were not affected or enhanced compared to the unamended control (up to 40% for BA and 180% for VA). BP was not or negatively affected (up to70%). No clear trend was found for BR in the Ni treatment; in the BC treatment BR was enhanced by 63-69%. BGE was reduced in both treatments. The strongest effects on BCC profiles as determined by 16S rDNA denaturing gradient gel electrophoresis were due to incubation time treatment particularly for BC. BP was not or negatively (-38-70%) influenced. A phylotype corresponding to a specific BC band was closely related to Acinetobacter oleivorans DR1. Thus, this experimental study confirms potential anthropogenic influences for the bacterial and viral community on aggregates in the Bay of Noumea.

Black carbon-rich (BC) aerosols from natural and anthropogenic sources have the potential to change bacterial diversity, microbe-mediated food web processes, biogeochemical cycles and ecosystem functioning. Here, we explore this hypothesis by in situ and experimental investigations in the barrier reef system of New Caledonia. After an in situ deposition event of BC-rich aerosols (originating from a Nickel power plant) into the lagoon and off-reef system, bacterial production and biomass was elevated; particularly in the off-reef site, where attached bacterial production was measurable for the first time in long-term studies. This enhancing effect of BC-rich aerosols was also detected in roof-top and laboratory experiments with reference and in situ BC material. Concurrently, bacterial community composition (BCC) as assessed by 16S rDNA PCR based denaturing gradient gel electrophoresis (DGGE) changed upon BC in situ deposition and was also detectable in the attached fraction (no DNA amplification products were observed in previous studies for the attached fraction in off-reef sites without BC deposition events). In addition, experimental studies also revealed changes in BCC, particularly in experiments where organic particles were produced artificially thus further supporting the idea that BC-rich material is linked to particle formation. Sequence analyses of DGGE bands suggest that the reactions of the bacterial community to BC addition differed from other habitats. This study suggests that BC deposition can play a significant role for biodiversity and ecosystem functioning in the ocean.

Atmospheric input of anthropogenic lead increased globally over the last centuries. The present study shows that the concentrations of lead in sediment cores from low-productivity Hudson Bay, northern Canada, remained relatively constant over the last centuries. The lack of imprint of the increased anthropogenic lead input in this marine environment is not consistent with the increased lead concentrations in nearby lakes over the same period. In addition, the observed trend in lead isotopic composition in our cores suggests an apparent progressive overprint of anthropogenic lead during the 1900's. In other words, isotopes clearly registered the increasingly anthropogenic nature of lead in the sedimentary record, but total lead concentrations remained constant, indicating that some process limited the export of lead to the sediment. These observations point to a long-term limitation of the downward export of particles in Hudson Bay. Given that the source of lead was the same for both Hudson Bay and neighboring highproductivity lakes, we hypothesize that the very low primary productivity of Hudson Bay waters was responsible for the low vertical export of lead to marine sediments. We further propose that primary productivity is the most important factor that generally drives the vertical export of particulate matter, and thus hydrophobic contaminants, in near-oligotrophic marine environments.

Transparent Exopolymer Particles (TEP) have received considerable attention since they were first described in the ocean more than 20 years ago. This is because of their carbon-rich composition, their high concentrations in ocean’s surface waters, and especially because of their ability to promote aggregation due to their high stickiness (i.e. biological glue). As large aggregates contribute significantly to vertical carbon flux, TEP are commonly seen as a key factor that drives the downward flux of particulate organic carbon (POC). However, the density of TEP is lower than that of seawater, which causes them to remain in surface waters and even move upwards if not ballasted by other particles, which often leads to their accumulation in the sea surface microlayer. Hence we question here the generally accepted view that TEP always increase the downward flux of POC via gravitational settling. In the present reassessment of the role of TEP, we examine how the presence of a pool of non-sinking carbon-rich particulate organic matter in surface waters influences the cycling of organic carbon in the upper ocean at daily to decadal time scales. In particular, we focus on the role of TEP in the retention of organic carbon in surface waters versus downward export, and discuss the potential consequences of climate change on this process and on the efficiency of the biological carbon pump. We show that TEP sink only when ballasted with enough high-density particles to compensate their low density, and hence that their role in vertical POC export is not solely linked to their ability to promote aggregation, but also to their contribution to the buoyancy of POC. It follows that the TEP fraction of POC determines the degree of retention and remineralization of POC in surface waters versus its downward export. A high TEP concentration may temporally decouple primary production and downward export. We identify two main parameters that affect the contribution of TEP to POC cycling; TEP stickiness, and the balance between TEP production and degradation rates. Because stickiness, production and degradation of TEP vary with environmental conditions, the role of TEP in controlling the balance between retention versus export, and hence the drawdown of atmospheric CO2 by the biological carbon pump, can be highly variable, and is likely to be affected by climate change.

Several protocols using different treatments (various mixtures of acids at different temperatures for mineralisation) or using several analysis instrumentations were tested with the aim to define the method allowing the analysis of some groups of elements. This study proposes a protocol of sample treatment and analysis permitting in a single batch the determination of 16 elements (Al, As, Ba, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Ti, V and Zn) with different chemical features such as volatile or refractory trace elements. This method is specifically adapted to chemical matrices found in unpolluted to moderately polluted atmospheric aerosol samples. Aerosol samples were digested using a mixture aqua regia/hydrofluoric acid at 130 °C during 2 h, and were then analysed with specifically tuned inductively coupled plasma-optical emission spectrometry.

Atmospheric fluxes of bio-available inorganic nitrogen (DIN, i.e. nitrate+ammonium) and phosphorus (DIP, i.e. phosphate) were measured in 2010, 2011 and 2013 at the sampling station of Cap Ferrat (Ligurian Sea). Wet and dry fluxes of DIN, averaged over three years, were 35 and 19 mmol m−2 yr−1, respectively. Most of the nitrate was deposited under dry form, whilst ammonia was twice more found in wet deposition. Wet and dry fluxes of DIP, averaged over three years, were 0.11 and 0.64 mmol m−2 yr-1, respectively. Atmospheric fluxes of DIN and DIP were compared with other photic zone nutrient input sources, physical and biological, i.e. winter convection, N2 fixation, and upward diffusion. Even if convection is by far the most important nutrient input for surface waters, atmospheric sources may be the second one, supplying more nutrients than diazotrophy and diffusion, particularly in conditions of water column stratification.

In 2013, as part of the French NAOS (Novel Argo Oceanic observing System) program, five profiling floats equipped with nitrate sensors (SUNA-V2) together with CTD and bio-optical sensors were deployed in the Mediterranean Sea. At present day, more than 500 profiles of physical and biological parameters were acquired, and significantly increased the number of available nitrate data in the Mediterra-nean Sea. Results obtained from floats confirm the general view of the basin, and the well-known west-to-east gradient of oligotrophy. At seasonal scale, the north western Mediterranean displays a clear temperate pattern sustained by both deep winter mixed layer and shallow nitracline. The other sampled areas follow a subtropical regime (nitracline depth and mixed layer depth are generally decoupled). Float data also permit to highlight the major contribution of high-frequency processes in controlling the nitrate supply during winter in the north western Mediterranean Sea and in altering the nitrate stock in subsurface in the eastern basin.

Nitrate, phosphate, and silicate concentration profiles were measured at monthly frequency at the DYFAMED time-series station (central Ligurian Sea) between 1991 and 2011. The resulting data set, which constitutes the longest open-ocean time-series in the Mediterranean Sea, underwent quality control. A reproducible climatological pattern was observed with an unprecedented resolution, confirming the typical seasonal cycle of mid-latitudes. In summer and autumn, when the water mass is well stratified, i.e. the mixed layer depth (MLD) is shallow, nutrient concentrations in surface are very low or under the detection limit. In winter, as a result of the MLD extent, nutrients are supplied to the surface layer. Then, nutrient concentrations progressively decrease during spring. MLD appears to play a key role in controlling nutrient availability in the surface layer, but a direct, quantitative relationship between MLD and nutrient concentrations is difficult to establish due to undersampling. Regarding nutrient molar ratios (N:P, Si:N, and Si:P), results show anomalous values compared to those of other oceanic regions, presumably due to strong influence of external sources. As a consequence, nutrient molar ratios exhibit a seasonal pattern, with, in particular, an increase of the N:P ratio in condition of stratification. Over the period 1991–2011, the DYFAMED data set reveals decadal trends in nitrate and phosphate concentrations in deep waters (+0.23% and –0.62%, respectively) resulting in increasing N:P and Si:P ratios (+1.14% and +0.85% per year, respectively). Such a long-term variability is presumably related to changes in water mass and/or changes in external sources, even if it is difficult to assess due to not enough concomitant data from atmospheric and riverine inputs.

Two profiling floats, equipped with nitrate concentration sensors were deployed in the northwestern Mediterranean from summer 2012 to summer 2013. Satellite ocean color data were extracted to evaluate surface chlorophyll concentration at float locations. Time series of mixed layer depths and nitrate and chlorophyll concentrations were analyzed to characterize the interplay between the physical-chemical and biological dynamics in the area. Deep convection (mixed layer depth > 1000 m) was observed in January-February, although high-nitrate surface concentrations could be already observed in December. Chlorophyll increase is observed since December, although high values were observed only in March. The early nitrate availability in subsurface layers, which is likely due to the permanent cyclonic circulation of the area, appears to drive the bloom onset. The additional nitrate supply associated to the deep convection events, although strengthening the overall nitrate uptake, seems decoupled of the December increase of chlorophyll.

Large amounts of soot are continuously deposited on the global ocean. Even though significant concentrations of soot particles are found in marine waters, the effects of these aerosols on ocean ecosystems are currently unknown. Using a combination of in situ and experimental data, and results from an atmospheric transport model, we show that the deposition of soot particles from an oil-fired power plant impacted biogeochemical properties and the functioning of the pelagic ecosystem in tropical oligotrophic oceanic waters off New Caledonia. Deposition was followed by a major increase in the volume concentration of suspended particles, a change in the particle size spectra that resulted from a stimulation of aggregation processes, a 5% decrease in the concentration of dissolved organic carbon (DOC), a decreases of 33 and 23% in viral and free bacterial abundances, respectively, and a factor~2 increase in the activity of particle-attached bacteria suggesting that soot introduced in the system favored bacterial growth. These patterns were confirmed by experiments with natural seawater conducted with both soot aerosols collected in the study area and standard diesel soot. The data suggest a strong impact of soot deposition on ocean surface particles, DOC, and microbial processes, at least near emission hot spots.

The temporal evolution of the vertical export flux at the DYFAMED time-series station (Ligurian Sea) over the last 20 years reveals a strong interannual variability. Winter convection allows particulate (and dissolved) matter to be vertically exported (“flush-down” effect). The efficiency of this process determines also the concentration of nutrients brought to surface waters and, therefore, the intensity of the subsequent phytoplankton bloom. The sequence “convection-bloom” is the main driving force of vertical export flux in this region. The present work attempts to better identify the parameters that control vertical export flux dynamics by observing a 20 year time-series in relation with the temporal variability of mixed layer depth and surface primary production. The consequences of a more stratified water column in the future on biological productivity and vertical export flux are pointed out.

Phytoplankton phenology is primarily affected by physical forcing. However, its quantification is far from being completely understood. Among the physical forcing factors, the mixed layer depth (MLD) is considered to have the strongest impact on phytoplankton dynamics, and consequently, on their phenology. The role of MLD variations in shaping the phytoplankton phenology was explored in the Mediterranean Sea, a basin displaying contrasting phenological regimes. A database of MLD estimations was merged with ocean color chlorophyll concentrations ([Chl]SAT) to generate concomitant annual MLD and [Chl]SAT cycles. Several indices were calculated to quantitatively analyze these cycles. The relevance of indices summarizing the temporal difference between main characteristics of MLD and [Chl]SAT cycles was emphasized. As previously observed, two dominant phenological regimes coexist in the Mediterranean Sea. The first is marked by a typical spring bloom, as in temperate regions. The second displays a low seasonality and an absence of an intense [Chl]SAT peak as in subtropical areas. The MLD is shown to play a key role in determining the dominant phenological regime in a given area. Results also show that regions having low seasonality display concomitant MLD and [Chl]SAT maxima, whereas [Chl]SAT peaks are generally observed 30 days after MLD peaks in regions with strongest seasonality. Over the whole basin, [Chl]SAT increase starts 1 month after the initiation of MLD deepening. Finally, after examining the impact of MLD on light and nutrient availability for phytoplankton, mechanisms were proposed to explain the time lags between MLD and [Chl]SAT increase and MLD and [Chl]SAT maxima.

The aim of this study was to investigate the chemical composition and cycling of dissolved organic matter (DOM), focusing on the influence of thermal stratification and mixing. Samples were collected at the surface, 500 m and 1500 m, in April, July and October 2004 at the DYFAMED time-series site in the North-western Mediterranean. High molecular weight (HMW) DOM was concentrated using ultrafiltration. The HMW DOM fraction was characterised by H-1 NMR, amino acid and neutral sugar analysis. Results were interpreted in the context of the wealth of information available on site DYFAMED. Three key observations were made. Firstly, the carbohydrate component of DOM decreased with depth, in agreement with previous studies, indicating degradation of this labile material. Secondly, the July surface water sample was particularly carbohydrate rich; it is proposed this may be the result of increased carbohydrate production by phytoplankton under low nutrient conditions, and accumulation in the surface layers due to stratification of the water column. Finally, the October samples showed a distinctly different chemical signature to the April and July samples, potentially indicating a shift from a net production system in the spring and summer to a net re-mineralisation system in autumn. The results of this study offer an insight into the dynamic nature of DOM at station DYFAMED. (C) 2013 Elsevier Ltd. All rights reserved.

In the last ten years, a productive collaboration has grown between the Laboratoire d’Océanographie de Villefranche (LOV), NKE and IFREMER to implement biogeochemical sensors on profiling floats. A first project (2003) was dedicated to the design of the so-called ProvBio floats (models A and B) that consisted of a PROVOR-CTS3 float instrumented with three new optical sensors: a Wetlabs transmissometer (C-Rover), a 3-wavelength Satlantic radiometer (OCR-503) and an “ECO3” Wetlabs sensor, measuring chlorophyll-a fluorescence, colored dissolved organic matter and particle backscattering coefficients (see First Success of ProvBio floats, Coriolis Letter n°5). Then, the integration of biogeochemical sensors continued in the framework of ProNuts project (2009, autonomously profiling the nitrate concentrations in the ocean: the pronuts project, Coriolis Letter n°8), by equipping a PROVOR with a nitrate concentration sensor. In parallel within the framework of the Carbocean EU project, the ProvCarbon and ProvDo floats were developed as in 2006 by fitting on a PROVOR a C-Rover and a 3830 Aanderaa optode, respectively. They were used to investigate new tools to assess marine carbon sources and sinks. These initial developments have led to a first invaluable dataset and to subsequent papers (Xing et al. 2012, Xing et al. 2011) and report (IOCCG 2011). Nevertheless, the above projects have grown partially dissociated, as related to specific and project-related needs, while a more integrated solution may have a lot of advantages. Undoubtedly, the scientific exploitation of data would be strongly improved if a unique multidisciplinary float, able to measure all accessible parameters, was available. Such a multidisciplinary float would also strongly reduce costs, by sharing the float itself, and by reducing deployment, validation and communication costs. The idea to merge all these sensors on the same profiling float was thus at the origin of the ProvBioII float project, which was developed in the framework of the remOcean and NAOS programs.

Dans le présent rapport sont exposés les résultats du projet ARC-MED réalisé avec un appui financier de l’Agence de l’Eau Rhône Méditerranée Corse. L’objectif principal de cette étude a été d’estimer quantitativement les charges rhodaniennes en contaminants organiques persistants entrant dans le Golfe du Lion: polychlorobiphényles (PCB), hydrocarbures aromatiques polycycliques (HAP), polybromodiphényléthers (PBDE), polychlorodibenzodioxines et furanes (PCDD/F) ainsi qu’un dérivé des pesticides organochlorés (p,p’-DDE),. Par ailleurs, la variabilité annuelle-saisonnière des teneurs en contaminants dans les diverses masses d’air a été étudiée pendant une année sur deux stations à la Seyne-sur-Mer et au Cap Ferrat. Ce suivi a permis également de caractériser la répartition des contaminants (formes particulaires et gazeuses) dans les masses d’air étudiées. Enfin, deux campagnes en mer ont été effectuées dans le Golfe du Lion. Ces campagnes ont fourni des références marines des teneurs en contaminants dissous et particulaires dans le pro-delta du Rhône et dans le Golfe du Lion.

The semi-enclosed nature of the Mediterranean Sea, together with its smaller inertia due to the relative short residence time of its water masses, make it highly reactive to external forcings, in particular variations of water, energy and matter fluxes at the interfaces. This region, which has been identified as a “hotspot” for climate change, is therefore expected to experience environmental impacts that are considerably greater than those in many other places around the world. These natural pressures interact with the increasing demographic and economic developments occurring heterogeneously in the coastal zone, making the Mediterranean even more sensitive. This review paper aims to provide a review of the state of current functioning and responses of Mediterranean marine biogeochemical cycles and ecosystems with respect to key natural and anthropogenic drivers and to consider the ecosystems’ responses to likely changes in physical, chemical and socio-economical forcings induced by global change and by growing anthropogenic pressure at the regional scale. The current knowledge on and expected changes due to single forcing (hydrodynamics, solar radiation, temperature and acidification, chemical contaminants) and combined forcing (nutrient sources and stoichiometry, extreme events) affecting the biogeochemical fluxes and ecosystem functioning are explored. Expected changes in biodiversity resulting from the combined action of the different forcings are proposed. Finally, modeling capabilities and necessity for modeling are presented. A synthesis of our current knowledge of expected changes is proposed, highlighting relevant questions for the future of the Mediterranean ecosystems that are current research priorities for the scientific community. Finally, we discuss how these priorities can be approached by national and international multi-disciplinary research, which should be implemented on several levels, including observational studies and modeling at different temporal and spatial scales.

Climatic and anthropogenic changes are able to engender modifications in the aerosol composition at different geographical and temporal scales. The present study addresses this question for the trace metal concentrations

Atmospheric dry deposition of nitrogen (N) and dinitrogen (N-2) fixation rates were assessed in 2004 at the time-series DYFAMED station (northwestern Mediterranean, 43 degrees 25'N, 7 degrees 52'E). The atmospheric input was monitored over the whole year. Dinitrogen fixation was measured during different seasonal trophic states (from mesotrophy to oligotrophy) sampled during nine cruises. The bioavailability of atmospherically deposited nutrients was estimated by apparent solubility after 96h. The solubility of dry atmospheric N deposition was highly variable (from similar to 18% to more than 96% of total N). New N supplied to surface waters by the dry atmospheric deposition was mainly nitrate (NO3-) (similar to 57% of total N, compared to similar to 6% released as ammonium (NH4+)). The mean bioavailable dry flux of total N was estimated to be similar to 112 mu mol m(-2) d(-1) over the whole year. The NO3- contribution (70 mu mol NO3- m(-2) d(-1)) was much higher than the NH4+ contribution (1.2 mu mol NH4+ m(-2) d(-1)). The N:P ratios in the bioavailable fraction of atmospheric inputs (122.5-1340) were always much higher than the Redfield N: P ratio (16). Insoluble N in atmospheric dry deposition (referred to as ``organic'' and believed to be strongly related to anthropogenic emissions) was similar to 40 mu mol m(-2) d(-1). N-2 fixation rates ranged from 2 to 7.5 nmol L-1 d(-1). The highest values were found in August, during the oligotrophic period (7.5 nmol L-1 at 10 in depth), and in April, during the productive period (4 nmol L-1 d(-1) at 10 m depth). Daily integrated values of N-2 fixation ranged from 22 to 100 mu mol N m(-2) d(-1), with a maximum of 245 mu mol N m(-2) d(-1) in August. No relationship was found between the availability of phosphorus or iron and the observed temporal variability of N-2 fixation rates. The atmospheric dry deposition and N-2 fixation represented 0.5-6% and 1-20% of the total biological nitrogen demand, respectively. Their contribution to new production was more significant: 1-28% and 2-55% for atmospheric dry deposition and N-2 fixation, respectively. The dry atmospheric input was particularly significant in conditions of water column stratification (16-28% of new production), while N2 fixation reached its highest values in June (46% of new production) and in August (55%). (C) 2007 Elsevier Ltd. All rights reserved.

Wet atmospheric deposition of dissolved N, P and Si species is studied in well-mixed coastal ecosystem to evaluate its potential to stimulate photosynthetic activities in nutrient-depleted conditions. Our results show that, during spring, seawater is greatly depleted in major nutrients: Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Silicic acid (Si), in parallel with an increase of phytoplanktonic biomass. In spring (March to May) and summer (June to September), wet atmospheric deposition is the predominant source (> 60%, relative to riverine contribution) for nitrates and ammonium inputs to this N-limited coastal ecosystem. During winter (October to February), riverine inputs of DIN predominate (> 80%) and are annually the most important source of DIP (> 90%). This situation allows us to calculate the possibility for a significant contribution to primary production in May 2003, from atmospheric deposition (total input for DIN ≈ 300 kg.km-2.month-1). Based on usual Redfield ratios and assuming that all of the atmospheric-derived N (AD-N) in rainwater is bioavailable for phytoplankton growth, we can estimate new production due to AD-N of 950 mgC.m-2.month-1, during this period of depletion in the water column. During the same episode (May 2003), photosynthetic activity rate, considered as gross primary production, was estimated to approximately 30300 mgC.m-2.month-1. Calculation indicates that new photosynthetic activity due to wet atmospheric inputs of nitrogen could be up to 3 %.

A minor river in eastern Corsica is highly contaminated by an abandoned realgar mine. Its As and Sb net supply to the Tyrrhenian Sea is assessed, with emphasize on their behaviour in the mixing zone, where their concentrations strongly increase, probably in relation with the organic matter content