<div><p>While a rich history of patchiness research has explored spatial structure in the ocean, there is no consensus over the controls on biological patchiness and how physical-ecological-biogeochemical processes and patchiness relate. The prevailing thought is that physics structures biology, but this has not been tested at basin scale with consistent in situ measurements. Here we use the slope of the relationship between variance vs spatial scale to quantify patchiness and ~650,000 nearly continuous (dx ~200 m) measurements -representing the Atlantic, Pacific, and Southern Oceans -and find that patchiness of biological parameters and physical parameters are uncorrelated. We show variance slope is an emergent property with unique patterns in biogeochemical properties distinct from physical tracers, yet correlated with other biological tracers. These results provide context for decades of observations with different interpretations, suggest the use of spatial tests of biogeochemical model parameterizations, and open the way for studies into processes regulating the observed patterns.</p></div>

In France, the presence of marine microalgae of the genus Ostreopsis has been identified repeatedly on the Mediterranean coast for several years, whereas on the French Basque coasts its presence is much more recent. In the summers of 2021 and 2022, major Ostreopsis flowering episodes were reported on the Basque coast, resulting in several hundred cases of intoxication among holidaymakers and residents. The main route of human exposure is inhalation of aerosols, although it is not yet known whether the agents responsible for poisoning are Ostreopsis cells, cell debris, known toxins produced by Ostreopsis, or other as yet unidentified compounds. Other routes of exposure (dermal contact, eye contact, ingestion of contaminated water or seafood) are also possible. Poisoning is manifested through various signs and symptoms, occurring within 48 hours of exposure (Neurosensory and neurological, respiratory, dermal and digestive). This document presents the opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), established from the work of its WATER and ERCA Expert Committees. ANSES received a request from the Directorate General for Health (DGS) and the Directorate General for Food (DGAL) to update knowledge about Ostreopsis that had been reported in the Agency's opinions from 2007 and 2008 (ANSES, 2007 and 2008), and draw up specific recommendations for managing Ostreopsis proliferation on the Basque coast. The literature review conducted as part of this expert appraisal revealed that knowledge about the genus Ostreopsis (diversity, biology, ecology, toxins produced) is still too fragmentary to characterise the hazard and risk to human health. Nevertheless to help local authorities affected by Ostreopsis blooms, Agency proposes a surveillance and quality monitoring strategy based on collaboration between site managers and the regional health agencies (ARSs), applicable to sites currently subject to bathing water quality monitoring and water sports sites that meet the conditions below.

Reports of the benthic dinoflagellate Ostreopsis spp. have been increasing in the last decades, especially in temperate areas. In a context of global warming, evidences of the effects of increasing sea temperatures on its physiology and its distribution are still lacking and need to be investigated. In this study, the influence of temperature on growth, ecophysiology and toxicity was assessed for several strains of O. cf. siamensis from the Bay of Biscay (NE Atlantic) and O. cf. ovata from NW Mediterranean Sea. Cultures were acclimated to temperatures ranging from 14.5 ◦C to 32 ◦C in order to study the whole range of each strain-specific thermal niche. Acclimation was successful for temperatures ranging from 14.5 ◦C to 25 ◦C for O. cf. siamensis and from 19 ◦C to 32 ◦C for O. cf. ovata, with the highest growth rates measured at 22 ◦C (0.54–1.06 d-1) and 28 ◦C (0.52–0.75 d-1), respectively. The analysis of cellular content of pigments and lipids revealed some aspects of thermal acclimation processes in Ostreopsis cells. Specific capacities of O. cf. siamensis to cope with stress of cold temperatures were linked with the activation of a xanthophyll cycle based on diadinoxanthin. Lipids (neutral reserve lipids and polar ones) also revealed species-specific variations, with increases in cellular content noted under extreme temperature conditions. Variations in toxicity were assessed through the Artemia franciscana bioassay. For both species, a decrease in toxicity was observed when temperature dropped under the optimal temperature for growth. No PLTX-like compounds were detected in O. cf. siamensis strains. Thus, the main part of the lethal effect observed on A. franciscana was dependent on currently unknown compounds. From a multiclonal approach, this work allowed for defining specificities in the thermal niche and acclimation strategies of O. cf. siamensis and O. cf. ovata towards temperature. Potential impacts of climate change on the toxic risk associated with Ostreopsis blooms in both NW Mediterranean Sea and NE Atlantic coast is further discussed, taking into account variations in the geographic distribution, growth abilities and toxicity of each species.

Fast environmental changes and high coastal human pressures and impacts threaten the Mediterranean Sea. Over the last decade, recurrent blooms of the harmful dinoflagellate Ostreopsis cf. ovata have been recorded in many Mediterranean beaches. These microalgae produce toxins that affect marine organisms and human health. Understanding the environmental conditions that influence the appearance and magnitude of O. cf. ovata blooms, as well as how climate change will modify its future distribution and dynamics, is crucial for predicting and managing their effects. This study investigates whether the spatio-temporal distribution of this microalga and the frequency of its blooms could be altered in future climate change scenarios in the Mediterranean Western basin. For the first time, an ecological habitat model (EHM) is forced by physico-chemical climate change simulations at high-resolution, under the strong greenhouse gas emission trajectory (RCP8.5). It allows to characterize how O. cf. ovata may respond to projected conditions and how its distribution could shift over a wide spatial scale, in this plausible future. Before being applied to the EHM, future climate simulations are further refined by using a statistical adaptation method (Cumulative Distribution Function transform) to improve the predictions robustness. Temperature (optimum 23–26 °C), high salinity (>38 psu) and high inorganic nutrient concentrations (nitrate >0.25 mmol N·m$^{−3}$ and phosphate >0.035 mmol P·m−3) drive O. cf. ovata abundances. High spatial disparities in future abundances are observed. Namely, O. cf. ovata abundances could increase on the Mediterranean coasts of France, Spain and the Adriatic Sea while a decrease is expected in the Tyrrhenian Sea. The bloom period could be extended, starting earlier and continuing later in the year. From a methodological point of view, this study highlights best practices of EHMs in the context of climate change to identify sensitive areas for current and future harmful algal blooms.

Abstract Dinoflagellates are marine organisms that undergo seasonal explosive proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in these events. However, mechanistical understanding of mitosis and cytokinesis in dinoflagellate remains rudimentary. Using an optimized immunofluorescence protocol, we analysed changes in microtubule organization occurring during the mitotic cycle of the toxic dinoflagellate Ostreopsis cf. ovata. This study revealed important features of dinoflagellate cell division. We find that the two flagella and the cortical microtubule array persist throughout the mitotic cycle. Two microtubule bundles are present in the cytoplasm originating from the ventral area, where the basal bodies are located: a cortical bundle and a cytoplasmic ventral bundle. The latter associates with the nucleus in the cell centre in preparation for mitosis and with the acentrosomal extranuclear spindle during mitosis. Analysis of tubulin post-translational modifications identifies two populations of spindle microtubules: polar acetylated microtubules whose length is stable throughout mitosis and central tyrosinated microtubules which elongate during chromosome segregation. During cell division a microtubule rich structure forms along the dorsal-ventral axis, associated with the site of cytokinesis, consistent with a cytokinetic mechanism independent of the actomyosin ring typical of animal and yeast cells. Summary statement Our study describes special features of mitosis and cytokinesis in dinoflagellates and uncovers a new alternative mechanism for cell division, highlighting the plasticity of cell biological process in eukaryotic cells.

Blooms of Ostreopsis cf. ovata pose an emerging health threat, causing respiratory disorders in various coastal regions. This dinoflagellate produce potent phycotoxins named ovatoxins that can be transferred from the seawater to the atmosphere. However, the biotic and abiotic conditions affecting their transfer are still unknown. In this study, we investigate the sea-to-air transfer of O. cf ovata phycotoxins using a process study in an aerosol reference tank (MART) and field observations. The process study exhibited a positive correlation between the phycotoxin content in sea spray aerosol (up to 832.59 ng m -3 ) and the particulate phycotoxin fraction in the water column and surface microlayer. In contrast, in the natural system, aerosolized phycotoxins were only observed in one out of six air collection (total toxins 0.59 ng m -3 ) despite optimal wind conditions. In both the process study and the natural system, ovatoxins represented only a minor fraction of the total toxin content, which was comprised of up to 90% liguriatoxins. In seawater, while no solubilized ovatoxins were detected, the concentration in dissolved liguriatoxin-a reached up to 19.07 μg L -1 . These results underscore the need for future research on the liguriatoxins, and on their toxicity to establish safe exposure thresholds for beachgoers.

Abstract Dinoflagellates are marine organisms that undergo seasonal explosive proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in these events. However, mechanistical understanding of mitosis and cytokinesis in dinoflagellate remains rudimentary. Using an optimized immunofluorescence protocol, we analysed changes in microtubule organization occurring during the mitotic cycle of the toxic dinoflagellate Ostreopsis cf. ovata. This study revealed important features of dinoflagellate cell division. We find that the two flagella and the cortical microtubule array persist throughout the mitotic cycle. Two microtubule bundles are present in the cytoplasm originating from the ventral area, where the basal bodies are located: a cortical bundle and a cytoplasmic ventral bundle. The latter associates with the nucleus in the cell centre in preparation for mitosis and with the acentrosomal extranuclear spindle during mitosis. Analysis of tubulin post-translational modifications identifies two populations of spindle microtubules: polar acetylated microtubules whose length is stable throughout mitosis and central tyrosinated microtubules which elongate during chromosome segregation. During cell division a microtubule rich structure forms along the dorsal-ventral axis, associated with the site of cytokinesis, consistent with a cytokinetic mechanism independent of the actomyosin ring typical of animal and yeast cells. Summary statement Our study describes special features of mitosis and cytokinesis in dinoflagellates and uncovers a new alternative mechanism for cell division, highlighting the plasticity of cell biological process in eukaryotic cells.

Au cours des dernières décennies, les dinoflagellés du genre Ostreopsis ont été identifiés dans les eaux marines de plusieurs pays européens tels que l’Albanie, la Croatie, Chypre, l'Espagne, la France, la Grèce, l'Italie, Monaco et le Portugal . Ces microalgues sont principalement benthiques et vivent de préférence sur des substrats biotiques, comme des macrophytes (macroalgues et phanérogames marines). Elles peuvent néanmoins se retrouver en suspension dans l’eau (elles sont alors planctoniques) ou même former des agrégats en surface, on les nomme alors fleurs d’eau. Ces microalgues peuvent causer des intoxications humaines lorsque les cellules ou les toxines qu’elles produisent sont présentes dans l’eau de mer, dans les embruns et aérosols ou dans certains produits de la mer. L’exposition peut se faire : • par voie respiratoire (inhalation et/ou contact avec les aérosols lors de promenade, de surveillance des plages, des activités de baignade et nautiques, etc.) ; • par contact cutané avec de l’eau de mer ou des macrophytes, support d’Ostreopsis (lors des activités de baignade et/ou nautiques) ; • par ingestion d’eau de mer lors de la baignade ou de pratiques d’activités nautiques ou encore en cas de consommation de produits de la mer contaminés par des toxines produites par Ostreopsis spp. Des manifestations cliniques telles que toux, rhinorrhée, irritations de la sphère ORL et des yeux, céphalées, fièvre, difficultés respiratoires, nausées, vomissements, diarrhées, douleurs abdominales, myalgies, rougeurs ou démangeaisons sont alors observées chez les personnes exposées à Ostreopsis. En France, la présence d’Ostreopsis est identifiée de façon récurrente sur les côtes méditerranéennes depuis une quinzaine d’années. Plus récemment, 674 personnes ont développé des signes et des symptômes associés aux proliférations d’Ostreopsis sur la côte basque française durant l’été 2021. Le bilan épidémiologique de ces intoxications montre qu’il n’existe pas de différence clinique avec les effets observés lors des épisodes de prolifération d’Ostreopsis cf. ovata du pourtour méditerranéen. Les investigations menées par l’Ifremer ont mis en évidence sur la côte basque la présence de deux espèces de microalgues du genre Ostreopsis pendant les épisodes de proliférations de 2021 et 2022 : O. cf. siamensis et O. cf. ovata. Si la première, O. cf. siamensis, est présente sur cette côte depuis 2018, la seconde, O. cf. ovata, a été identifiée dans cette partie du golfe de Gascogne pour la première fois en 2021. Ostreopsis cf. ovata est connue pour produire des toxines dont la structure est proche de celle de la palytoxine (PLTX). Ces molécules pourraient être à l’origine des symptômes observés dans les populations humaines, d’autant plus que certaines d’entre elles ont été détectées dans les aérosols en Méditerranée.

Au cours des dernières décennies, plusieurs espèces de dinoflagellés du genre Ostreopsis ont été identifiées dans les eaux marines de pays européens tels que l’Albanie, la Croatie, Chypre, l'Espagne, la France, la Grèce, l'Italie, Monaco et le Portugal. Ces microalgues peuvent causer des intoxications humaines lorsque les cellules ou les toxines qu’elles produisent sont présentes dans l’eau de mer, les aérosols ou dans certains produits de la mer. La voie principale d’exposition de l’Homme est l’inhalation d’aérosols sans que l’on sache actuellement si les agents à l’origine des intoxications sont les cellules d’Ostreopsis, les débris cellulaires, des toxines connues produites par Ostreopsis ou d’autres composés non encore identifiés. D’autres voies d’exposition (contact cutané, contact oculaire, ingestion d’eau ou de produits de la mer contaminés) sont possibles. Les intoxications se manifestent par divers signes et symptômes (survenant moins de 48h après l’exposition) : - neurosensoriels et neurologiques : paresthésies (sensation de fourmillements), dysesthésies (sensation de brûlure) et céphalées ; - respiratoires, de la sphère ORL et stomatologiques : dysgueusie à type de goût métallique, rhinorrhée, toux, gêne respiratoire ; - cutanés évoquant de l’urticaire ; - cardiaques : tachycardie, poussée hypertensive ; - digestifs : nausées, vomissements, diarrhée ; - systémiques : fièvre ; - locomoteurs : myalgies et arthralgies (douleurs musculaires et articulaires). Elles surviennent lors de diverses situations : - travail ou activités récréatives dans la mer (baigneurs, maîtres-nageurs, pêcheurs professionnels, surfeurs, etc.) ; - travail ou activités récréatives sur ou à proximité de la plage (estivants, secouristes, agents en charge du nettoyage des plages, restaurateurs, etc.) ; - séjour ou résidence à proximité immédiate du bord de mer ; - consommation de produits de la mer contaminés. En France, la présence d’Ostreopsis est identifiée de façon récurrente sur les côtes méditerranéennes depuis une quinzaine d’années alors qu’elle est beaucoup plus récente sur les côtes basques française et espagnole. Deux espèces ont été identifiées sur la côte basque : O. cf. siamensis et O. cf. ovata. Si la première, O. cf. siamensis, est observée sur cette côte depuis 2018, la seconde, O. cf. ovata, a été observée dans cette partie du golfe de Gascogne pour la première fois en 2021. Le bilan épidémiologique montre que près de 900 personnes ont développé des signes et des symptômes associés aux proliférations d’Ostreopsis sur la côte basque française depuis 2020. Ce bilan montre par ailleurs qu’il n’existe pas de différence clinique avec les effets observés lors des épisodes de prolifération d’Ostreopsis cf. ovata du pourtour méditerranéen. [Saisines liées n°2007-SA-0227 et 2007-SA-0303]

This paper summarizes the research conducted by the partners of the EU co-funded CoCliME project to ascertain the ecological, human health and economic impacts of Ostreopsis (mainly O. cf. ovata) blooms in the NW Mediterranean coasts of France, Monaco and Spain. This knowledge is necessary to design strategies to prevent, mitigate and, if necessary, adapt to the impacts of these events in the future and in other regions. Ostreopsis proliferations in the Mediterranean have been related to massive mortalities of benthic organisms and to symptoms of respiratory and cutaneous irritation in humans. A six-year epidemiologic study in a Ostreopsis hot spot in Catalonia and the accumulated experience of the French Mediterranean National Ostreopsis Surveillance Network confirm the main effects of these blooms on human health in the NW Mediterranean. The impacts are associated to direct exposure to seawater with high Ostreopsis cell concentrations and to inhalation of aerosols containing unknown irritative chemicals produced under certain circumstances during the blooms. A series of mild acute symptoms, affecting the entire body as well as the ophthalmic, digestive, respiratory and dermatologic systems have been identified. A main remaining challenge is to ascertain the effects of the chronic exposure to toxic Ostreopsis blooms. Still, the mechanisms involved in the deletereous effects of Ostreopsis blooms are poorly understood. Characterizing the chemical nature of the harmful compounds synthesized by Ostreopsis as well as the role of the mucus by which cells attach to benthic surfaces, requires new technical approaches (e.g., metabolomics) and realistic and standardized ecotoxicology tests. It is also necessary to investigate how palytoxin analogues produced by O. cf. ovata could be transferred through the marine food webs, and to evaluate the real risk of seafood poisonings in the area. On the other hand, the implementation of beach monitoring and surveillance systems in the summer constitutes an effective strategy to prevent the impacts of Ostreopsis on human health. In spite of the confirmed noxious effects, a survey of tourists and residents in Nice and Monaco to ascertain the socioeconomic costs of Ostreopsis blooms indicated that the occurrence of these events and their impacts are poorly known by the general public. In relationship with a plausible near future increase of Ostreopsis blooms in the NW Mediterranean coast, this survey showed that a substantial part of the population might continue to go to the beaches during Ostreopsis proliferations and thus could be exposed to health risks. In contrast, some people would not visit the affected areas, with the potential subsequent negative impacts on coastal recreational and touristic activities. However, at this stage, it is too early to accurately assess all the economic impacts that a potentially increasing frequency and biogeographic expansion of the events might cause in the future.

In recent decades, recurrent Ostreopsis spp. blooms have been recorded throughout the globe, causing public health issues and mass mortalities of invertebrates. Ostreopsis species are benthic and develop in shallow waters in close relation with a substrate, but possible substrate preferences are still ambiguous. Bloom develops on both living and dead substrates and several interacting biotic and abiotic factors acting at different spatial scales can potentially foster or regulate Ostreopsis spp. development. The objective of this review is to collect and summarize information on Ostreopsis spp. blooms related to the habitat at different spatial scales, in order to assess preferences and trends. References including Ostreopsis spp. samplings in the field were analysed in this review, as potentially including information about the micro- (substrate), meso‑ (community) and macrohabitat (ecosystem) related to Ostreopsis spp. blooms. The sampled substrate and the ecosystem where Ostreopsis spp. were collected were generally reported and described in the studies, while the description of the mesohabitat was rarely reported. Ostreopsis spp. were generally described as attached to biotic substrates and in particular, macroalgae, even in studies conducted in coral reefs, where macroalgae are generally not dominant (but they can be in case of coral reef degradation). In both temperate and tropical areas, Ostreopsis spp. were mostly sampled on algal species usually forming medium or low complexity communities (erect or turf-forming algae), often characteristic from post-regime shift scenarios, and rarely on canopy-forming species (such as fucoids and kelps). This literature review highlights the need of collecting more information about the mesohabitat where important Ostreopsis spp. blooms develop, as much as of the underlying mechanisms driving eventual differences on Ostreopsis spp. abundances. This knowledge would allow a better risk assessment of Ostreopsis spp. blooms, identifying areas at high risk on the base of the benthic habitats

The dinoflagellate Ostreopsis cf. ovata produces several families of toxic polyketides. Despite only a few field measurements of these phycotoxins in seawater and aerosols, they are believed to be responsible for dermatitis and the toxic inhalations reported during blooms of this species. Therefore, the stability of these compounds in seawater is essential to understanding the causes of these symptoms, however, this has never been assessed. In the current study, the optimization of a solid phase extraction (SPE) procedure was first performed to ensure the most efficient extraction of all phycotoxins known to be produced by this strain, including the recently described liguriatoxins. The SPE cartridge SDBL® under non acidified conditions offered the best option. The stability of the ovatoxins and the liguriatoxins under biotic and abiotic stress was assessed by exposing the spent medium of a culture of Ostreopsis cf. ovata to its bacterial consortium and natural sunlight. A rapid biotic transformation was detected for both families of compounds. When exposed to bacteria, the half-lives of the ovatoxins were reached before 10 h and at 36 h, 97% of these toxins had been transformed. The half-lives of the liguriatoxins were 10 h under these conditions. Photolysis (abiotic degradation) of the ovatoxins (T1/2 < 36 h) was faster than for the liguriatoxins (T1/2 > 62 h). Although none of the catabolites of these phycotoxins were thoroughly identified, an untargeted metabolomics approach combined with molecular networking highlighted the presence of several compounds exhibiting structural similarities with the ovatoxins. Additional work should confirm the preliminary findings on these potential ovatoxins’ catabolites and their biological properties. The rapid transformation of O. cf. ovata’s phycotoxins introduces questions concerning their presence in seawater and their dispersion in the sea spray aerosols. The compounds involved in the toxic inhalations and dermatitis often experienced by beachgoers may stem from the catabolites of these toxins or even unrelated and as yet unidentified compounds.

Recurrent blooms of the toxic dinoflagellate Ostreopsis cf. ovata are frequently reported in the Northwestern Mediterranean Sea. The impact of these proliferations on other microalgal species inhabiting the same habitats is of interest from an ecological prospective. In vitro experiments were carried out to investigate the influence of O. cf. ovata on the growth of the co-occurring benthic diatoms Licmophora paradoxa, Navicula arenaria and the benthic dinoflagellates Prorocentrum lima and Coolia monotis. Overall, O. cf. ovata exhibited weak allelopathic effects towards these microalgal species, with a reduction in the cell abundance for L. paradoxa and P. lima only. Interestingly, dead cells of L. paradoxa and N. arenaria were observed embedded in the thick mucus surrounding O. cf. ovata cells, suggesting that the mucous layer could act as a toxic phycosphere, especially for non-motile cells. All competitors were further exposed for 24 h to ovatoxins, the major toxins produced by O. cf. ovata, and the maximum quantum yield efficiency of L. paradoxa, N. arenaria and P. lima was affected at a minimum concentration of 10 µg mL−1. We then hypothesized that the diffusion of solubilized ovatoxins in the culture medium affects only moderately the competitors’ growth, whereas their accumulation in the mucus would yield deleterious effects. More precisely, the competitors’ sensitivity to ovatoxins was enhanced in their stationary phase of growth and resulted from a rapid inhibition of an uncharacterized photosynthetic step downstream photosystem II. Altogether, these results emphasize the predominant role of the O. cf. ovata’s mucus in driving ecological interactions and suggest that it can affect the growth of several benthic microalgae by accumulating the potent ovatoxins.

This paper summarizes the research conducted by the partners of the EU co-funded CoCliME project to ascertain the ecological, human health and economic impacts of Ostreopsis (mainly O. cf. ovata) blooms in the NW Mediterranean coasts of France, Monaco and Spain. This knowledge is necessary to design strategies to prevent, mitigate and, if necessary, adapt to the impacts of these events in the future and in other regions. Ostreopsis proliferations in the Mediterranean have been related to massive mortalities of benthic organisms and to symptoms of respiratory and cutaneous irritation in humans. A six-year epidemiologic study in a Ostreopsis hot spot in Catalonia and the accumulated experience of the French Mediterranean National Ostreopsis Surveillance Network confirm the main effects of these blooms on human health in the NW Mediterranean. The impacts are associated to direct exposure to seawater with high Ostreopsis cell concentrations and to inhalation of aerosols containing unknown irritative chemicals produced under certain circumstances during the blooms. A series of mild acute symptoms, affecting the entire body as well as the ophthalmic, digestive, respiratory and dermatologic systems have been identified. A main remaining challenge is to ascertain the effects of the chronic exposure to toxic Ostreopsis blooms. Still, the mechanisms involved in the deletereous effects of Ostreopsis blooms are poorly understood. Characterizing the chemical nature of the harmful compounds synthesized by Ostreopsis as well as the role of the mucus by which cells attach to benthic surfaces, requires new technical approaches (e.g., metabolomics) and realistic and standardized ecotoxicology tests. It is also necessary to investigate how palytoxin analogues produced by O. cf. ovata could be transferred through the marine food webs, and to evaluate the real risk of seafood poisonings in the area. On the other hand, the implementation of beach monitoring and surveillance systems in the summer constitutes an effective strategy to prevent the impacts of Ostreopsis on human health. In spite of the confirmed noxious effects, a survey of tourists and residents in Nice and Monaco to ascertain the socioeconomic costs of Ostreopsis blooms indicated that the occurrence of these events and their impacts are poorly known by the general public. In relationship with a plausible near future increase of Ostreopsis blooms in the NW Mediterranean coast, this survey showed that a substantial part of the population might continue to go to the beaches during Ostreopsis proliferations and thus could be exposed to health risks. In contrast, some people would not visit the affected areas, with the potential subsequent negative impacts on coastal recreational and touristic activities. However, at this stage, it is too early to accurately assess all the economic impacts that a potentially increasing frequency and biogeographic expansion of the events might cause in the future.

The present study aims to identify epiphytic Ostreopsis cells collected in Guadeloupe between 2017 and 2018 using a morpho-molecular approach. This method combined microscopical observations of wild specimens (light and scanning electron microscopy) with a phylogenetic analysis inferred from concatenated sequences of ribosomal operon (SSU + ITS + LSU) of Ostreopsidoideae. Four distinct morphotypes were identified in our samples and studied by SEM. Molecular data obtained from single-cell PCR for the four morphotypes were consistent with observations and confirmed the presence of three Ostreopsis species resolved in well characterized genotypes (O. cf. ovata, O. lenticularis and O. siamensis) and an unidentified clade. Detailed morphological characters including sulcal plates confirmed the identification of the last morphotype as O. heptagona D.R. Norris, J.W. Bomber & Balech, which forms a new basal clade in the genus, not previously reported. Observations highlighted overlapping sizes for O. lenticularis, O. siamensis and O. heptagona. Direct sequencing of PCR products obtained for some cells of O. lenticularis and O. heptagona collected at one site revealed unexpectedly the presence of the parasitoid dinoflagellate Amoebophrya. Some Ostreopsis cells were found partially emptied and exhibiting a compact mass. Further analyses are needed to understand the ecological role of Amoebophrya on blooms of epiphytic Ostreopsis species.

Summary In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic.

The PHYTOBS dataset includes long-term time series on marine microphytoplankton, since 1987, along the whole French metropolitan coast. Microphytoplankton data cover microscopic taxonomic identifications and counts. The whole dataset is available, it includes 25 sampling locations. PHYTOBS network studies microphytoplankton diversity in the hydrological context along French coasts under gradients of anthropogenic pressures. PHYTOBS network allows to analyse the responses of phytoplankton communities to environmental changes, to assess the quality of the coastal environment through indicators, to define ecological niches, to detect variations in bloom phenology, and to support any scientific question by providing data. The PHYTOBS network provides the scientific community and stakeholders with validated and qualified data, in order to improve knowledge regarding biomass, abundance and composition of marine microphytoplankton in coastal and lagoon waters in their hydrological context. PHYTOBS originates of two networks. The historical REPHY (French Observation and Monitoring program for Phytoplankton and Hydrology in coastal waters) supported by Ifremer since 1984 and the SOMLIT (Service d'observation en milieu littoral) supported by INSU-CNRS since 1995. The monitoring has started in 1987 on some sites and later in others. Hydrological data are provided by REPHY or SOMLIT network as a function of site locations.

Ostreopsis cf. ovata is a benthic dinoflagellate very common in tropical and temperate coastal areas, particularly in the Mediterranean Sea. This species is also found in the plankton, i.e. swimming in the water column or in aggregates floating at the sea surface. The potential links between the planktonic and benthic populations influencing their relative distribution in the water column and attached to the benthic substrate are poorly understood. To shed light on this question, a high-frequency temporal monitoring was conducted in the Villefranche bay (France) to determine the abundance of (1) epibenthic cells attached to macroalgae, (2) planktonic cells in the water column and (3) cells in aggregates floating at the sea water surface (hereafter, referred to sea surface cells) . This monitoring was realized over 3 consecutive years (2018, 2019 and 2020) and at different phases of the bloom (exponential phase – 2020, peak – 2019 and decline phase – 2018). Strong variations in benthic and planktonic O. cf. ovata abundances were observed over the 24 h sampling cycles conducted in three consecutive years. The three populations, planktonic, benthic and sea surface cells, exhibited the highest numbers during the day (light) hours and lowest values at night in 2018 and 2019. In 2020, however, benthic abundances did not differ significantly between light and dark periods. Moreover, epibenthic cells abundances peaked in the morning, followed by the peak of the cells in the plankton and in the surface aggregates during the afternoon. Monitoring of O. cf. ovata is often based on a single sampling per day without precise indications of sampling time and shows great variability in O. cf. ovata abundances. Our observations of daily variations in cell abundances along the water column clearly indicate that time and water column depth of sampling constitute a great source of variability and have to be considered when designing new monitoring strategies to reduce variability and to harmonize data acquisition and international comparisons.

Phycotoxins synthesized by benthic dinoflagellates are known to bioaccumulate in macrofauna and hence represent a risk for human health. However, the presence of toxins synthesized by benthic dinoflagellates in smaller marine organisms than macrofauna has not been considered despite the fact that such small organisms have an important ecological role in the benthic food web. This present study quantified, for the first time, the trophic relationship between benthic dinoflagellates and meiofauna by using stable isotope enriched dinoflagellates during ingestion experiments. Results showed that harpacticoid copepods were not able to discriminate, during ingestion, between the potentially toxic cells of Ostreopsis cf. ovata and the non-toxic cells of Amphidinium cf. carterae, even when another food resource, such as diatoms (e.g. Odontella sp.), was provided (Kruskal Wallis test, p > 0.05).

Macrophage Migration Inhibitory Factors (MIF) are pivotal cytokines/chemokines for vertebrate immune systems. MIFs are typically soluble single-domain proteins that are conserved across plant, fungal, protist, and metazoan kingdoms, but their functions have not been determined in most phylogenetic groups. Here, we describe an atypical multidomain MIF protein. The marine dinoflagellate Lingulodinium polyedra produces a transmembrane protein with an extra-cytoplasmic MIF domain, which localizes to cell-wall-associated membranes and vesicular bodies. This protein is also present in the membranes of extracellular vesicles accumulating at the secretory pores of the cells. Upon exposure to biotic stress, L. polyedra exhibits reduced expression of the MIF gene and reduced abundance of the surface-associated protein. The presence of LpMIF in the membranes of secreted extracellular vesicles evokes the fascinating possibility that LpMIF may participate in intercellular communication and/or interactions between free-living organisms in multispecies planktonic communities.

From January 2011 to March 2018, 26 patients aged from 20 to 80 years old reported being sick in France after eating sea figs of the genus Microcosmus. The patients had symptoms evoking a cerebellar syndrome: blurred or double vision, ataxia and dizziness, asthenia, headache, muscle cramps, paresthesia and digestive disorders (nausea, vomiting and diarrhea). Three of the 18 food poisoning events recorded by the Poison Control Center in Marseille and involving four patients were further investigated as the meal leftovers were collected and analyzed. A previous study ruled out the presence of the regulated lipophilic marine toxins after high-resolution mass spectrometry, but further analyses were required to look for hydrophilic cyanotoxins. The sea fig leftovers from food poisoning case Numbers 1 (January 2011), 6 (December 2012) and 17 (March 2018) of this published case series were analyzed by hydrophilic interaction liquid chromatography coupled to low-and high-resolution mass spectrometry to investigate the presence of hydrophilic cyanotoxins. The sea fig samples showed anatoxin-a (ATX-a) concentrations ranging from 193.7 to 1240.2 µg/kg. The sea fig control sample analyzed was also contaminated with ATX-a but in a much smaller concentration (22.5 µg/kg). To the best of our knowledge, this is the first report of human food poisoning involving ATX-a as the possible causative toxin where the cyanotoxin could be unequivocally identified.

For the first time, distribution of epiphytic dinoflagellates was studied in Saint Martin Island (Lesser Antilles) during the cyclonic season (between September 1 st and 3 rd 2015). The present study provides a semi-quantitative analysis because the fresh weight of each macrophyte was estimated around 10 g. The identified genera were: Ostreopsis, Prorocentrum, Coolia, Amphidinium, and Gambierdiscus in order of decreasing abundance. Highest average abundance values of the genera Ostreopsis and Amphidinium were hosted by macrophytes of the Phaeophyceae group with ca. 15,000 and 60 cells g-1 respectively. Epiphytic Coolia cells were mainly observed on seagrasses with the highest average abundance value of ca. 1000 cells g-1 whereas the genera Gambierdiscus and Prorocentrum were principally associated with Florideophyceae with the highest average abundances of ca. 70 and 1500 cells g FW-1 respectively. This preliminary study indicates the most relevant locations to survey the biodiversity of potentially toxic epiphytic dinoflagellates in Saint Martin Island.

The genus Ostreopsis includes some species that produce high biomass blooms and/or synthesize toxic compounds that can be transferred through the marine food webs or aerosolized causing ecological, human health and socioeconomic impacts. Ostreopsis species are increasing their biogeographic distribution from tropical to more temperate waters and causing recurrent blooms in certain coastal areas, thus constituting an emerging concern worldwide. The proliferation capacity of Ostreopsis is due to a complex and poorly understood combination of multiple factors, and may be a paradigm of chemical ecology reviewed here. A first section summarizes the basic knowledge on the different Ostreopsis species, the toxins they produce and the described foodborne and airborne effects of Ostreopsis toxins on humans. Secondly, direct and indirect interactions between Ostreopsis species and their environment are reviewed. Mucopolysaccharide substances produced by the cells to attach to different substrates appear to be a key element on the chemical ecology and requires further study. However, this research is challenged by technical limitations to conduct ecologically realistic and harmonized studies where organisms can be in direct contact with Ostreopsis cells, their mucus and/or the released extracellular toxic compounds. Understanding the transfer mechanisms of these substances within the food web, potentially affecting humans is critical and requires further study with new analytical tools. Still, the progress in knowledge achieved in the last years, combined with experimental and field studies using cutting edge methods will facilitate to address the open questions on the chemical ecology of Ostreopsis and understand its bloom dynamics now, and under future climate and anthropogenic change scenarios.

Harmful algal blooms are a source of increasing concern within the health, economic and ecological sectors. In the Mediterranean Sea, severe blooms of the benthic dinoflagellate Ostreopsis cf. ovata have been occurring since the beginning of the century, causing human intoxications by inhalation of bio-aerosols or direct contact with cells. The toxicity of this dinoflagellate is attributed to the presence of palytoxin and several of its analogs called ovatoxins, palytoxin being one of the most potent marine toxins. While mass mortalities of marine invertebrates have already been reported in relation with O. cf. ovata blooms, the toxic effects of this dinoflagellate on benthic organisms is still poorly documented. In the present study, laboratory experiments were performed on a meiobenthic copepod (Sarsamphiascus cf. propinquus), which naturally lives on macrophytes in close contact to O. cf. ovata, in order to assess its potential toxic effects on mortality, fecal pellet production (as a proxy of feeding), as well as fecundity and fertility ratios. Both, O. cf. ovata as well as a non-toxic competitive diatom (Licmophora paradoxa), were used as food in the experiments. Regarding acute toxicity evaluation, this copepod proved to be the most tolerant organism to O. cf. ovata reported to date. Nevertheless, its fecundity and fertility ratios were lower when fed with the toxic dinoflagellate, indicating a possible reprotoxic effect. Moreover, although fecal pellet production decreased significantly when the copepod was fed with a mono-diet of O. cf. ovata, epifluorescence microscopy observations revealed the presence of the toxic cells inside the digestive track, hence suggesting that these primary grazers could be a vector of toxins through the marine food web.

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.

For the first time, distribution and abundances (cells per gram of fresh macrophyte weight) of potentially toxic benthic dinoflagellates were studied around Guadeloupe (20 sites) and Martinique (six sites) islands (Lesser Antilles, Caribbean Sea). Benthic dinoflagellates were identified at the genus level and cell counts were undertaken on different host species of macroalgae and seagrasses. Abundance values of potentially toxic benthic dinoflagellates were one order of magnitude higher in Guadeloupe than in Martinique. The highest abundances of benthic dinoflagellates were found in the northern part of Guadeloupe Island, while their distribution was more homogeneous in Martinique. Ostreopsis was the dominant genus in Guadeloupe and Martinique. Regarding biotic substrate preferences, Phaeophyceae hosted the highest total abundances of benthic dinoflagellates on both islands, while the lowest total abundances were observed on Ulvophyceae in Guadeloupe and Florideophyceae in Martinique. The genus Gambierdiscus, known as the causal agent of the ciguatera fish poisoning (CFP), developed on all macrophyte groups on both islands without showing any preferences towards biotic substrates. The presence of this potentially harmful dinoflagellate genus in both islands could explain the existence of local cases of CFP in Guadeloupe and Martinique islands.

Ce cahier thématique des cahiers du GREC-SUD portant sur la santé et le changement climatique est destiné aux décideurs, gestionnaires de territoires et professionnels de santé. Il constitue une première approche pour mieux appréhender les conséquences du changement climatique en Provence-Alpes-Côte d’Azur.

For decades the microphytobenthos assemblage in the coastal Mediterranean Sea has been regularly colonized by the toxic benthic dinoflagellate Ostreopsis cf. ovata. This harmful algal species is a toxin producer and occupies the same ecological niche as various diatoms. Surprisingly, there are only few insights reported on the physiological responses of diatoms to blooms of O. cf. ovata The chemical interactions of O. cf. ovata with the co-occurring diatom Licmophora paradoxa was studied using a bioassay (measuring impact of cell-free culture filtrate) and a co-culture approach (separate by a membrane) to investigate the effects of the exometabolome and its mode of action. Bioassays highlighted a toxic effect of the exometabolome of O. cf. ovata on the diatom photosynthetic activity. However, the co-cultures revealed that these toxic effects do not occur through remote allelopathy. Contact or close interactions between cells of the two species is most likely needed to impair the diatom growth. Ovatoxins are suspected to be the toxic metabolites secreted by O. cf. ovata although the current set of data did not give confirmation of this assumption. Interestingly, the exometabolome of L. paradoxa impaired the growth and the photochemistry of O. cf. ovata in both bioassays and co-cultures. Some biomarkers possibly involved for the effect were identified using a metabolomic approach and may correspond to oxylipins, however a bacterial source of the bioactive metabolites is also considered.

Blooms of Ostreopsis cf. ovata, causing health incidence and mass human intoxications in the Mediterranean, gained special attention over the past decades. To study the potential effects of temperature and nutrient enrichment on this benthic dinoflagellate and other associated microalgae in situ, a multifactorial experiment was set up along a temperature gradient of a heat pump system in Monaco. Microalgae were quantified in experimental units, in the natural biofilm and in the water column. No significant interaction was observed between temperature and nutrients. A species- and bloom phase-dependent effect of the increased temperature was recorded, while the nutrient enrichment had a significant effect only at the end of the experiment (when cell abundances were low). Temperature effects were also visible in the biofilm and the surrounding water. The observed assemblages were mainly driven by changes in abundances of Ostreopsis cf. ovata and Actinocyclus sp., affected in different ways.

Toxic blooms of Ostreopsis spp. are greatly challenging to monitor due to the complexity and variability of cell repartition among benthic and pelagic compartments. This results in marked differences in employed methodologies for the survey of their dynamics and hampers the definition of the associated toxic risk. The present study aims at testing and improving common methodologies used for sampling, processing and counting of field samples. It contributes to the identification of the most suitable strategies for the monitoring and mitigation of Ostreopsis blooms in coastal waters. For a sampling based on the collection of macrophytes, the role of the fixative addition and of agitation steps in the efficiency of epiphytic cell collection was defined. For planktonic estimations, the influence of the volume used for concentrating water samples was characterized as a function of Ostreopsis cell abundance. The deployment of artificial substrates was tested and confirmed strong advantages of this new sampling methodology, including an integration of a part of the spatial and temporal variability of the cell distribution.

This paper describes the adoption and validation of two innovative methods for the automated count of Ostreopsis spp. concentration in sea water: a molecular assay based on RT-qPCR and an opto-electronic device implementing automatic recognition algorithms. The proposed approaches were tested on samples coming from different locations along the Mediterranean Sea and compared with the standard counting method based on microscopy observation by a taxonomy expert. The results demonstrate the effectiveness of both automatic approaches which provide a valuable tool, mostly cost and time effective, for the establishment of wide pan Mediterranean monitoring strategies of Ostreopsis spp. blooms. Moreover, the two automatic methods demonstrated the ability to discriminate for the presence of a different but similar species, O. fattorussoi, for which new species-specific qPCR primers were developed.

Despite the potential negative human health, ecological and economic impact, the ecology of harmful benthic dinoflagellate blooms remains largely unknown. This is probably due to the complex interactions among biotic and abiotic drivers that influence blooms, but also to the difficulty in quantifying cell abundance in a comparable way over large spatial and temporal scales. One of the recognized priorities for bHABs (benthic Harmful Algal Blooms) assessment is developing and standardizing methods that can provide comparable data. In this context, the Benthic Dinoflagellates Integrator (BEDI), a new non-destructive quantification method for benthic dinoflagellate abundances, has been developed and tested within the present study. The rationale behind the BEDI standard assessment method is that mechanical resuspension of cells enables the quantification of abundances as cells per unit of seabed surface area (i.e. cells mm−2) or as Potentially Resuspended cells per unit of volume (PRcells ml−1), by integrating both cells in the biofilm and those in the surrounding water. Estimations of Ostreopsis performed with BEDI method are independent of the substratum (i.e. macroalgal species) or the dominant ecosystem (i.e. algal forests or turfs, seagrass beds, coral reefs) and potentially allow the comparison of benthic dinoflagellate blooms over broad temporal and spatial scales. The first application of the BEDI method, presented in this study, gave encouraging results: the characterization of blooms of Ostreopsis cf. ovata at three sites in the NW Mediterranean Sea is consistent with results derived from the other commonly applied methods. Quantification of the ratio between abundances of cells in the biofilm and in the surrounding water was calculated for the first time per unit of seabed surface area, demonstrating that the highest abundances of cells (the stock), and therefore the associated risk for human health, are in the biofilm. For risk assessment purposes, conversion values for commonly used monitoring alert thresholds of Mediterranean Ostreopsis blooms are provided.

Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the 15N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH4+), nitrate (NO3−) and N-urea, from the estimation of kinetic and inhibition parameters. In the range of 0 to 10 μmol N L−1, kinetic curves showed a clear preference pattern following the ranking NH4+ > NO3− > N-urea, where the preferential uptake of NH4+ relative to NO3− was accentuated by an inhibitory effect of NH4+ concentration on NO3− uptake capabilities. Conversely, under high nutrient concentrations, the preference for NH4+ relative to NO3− was largely reduced, probably because of the existence of a low-affinity high capacity inducible NO3− uptake system. Ability to take up nutrients in darkness could not be defined as a competitive advantage for O. cf. ovata. Species competitiveness can also be defined from nutrient uptake kinetic parameters. A strong affinity for NH4+ was observed for O. cf. ovata cells that may partly explain the success of this toxic species during the summer season in the Bay of Villefranche-sur-mer (France).

Shallow, well-illuminated coastal waters from tropical to temperate latitudes are attractive environments for humans. Beaches and coral reefs have provided lodging and food to coastal communities for centuries. Unfortunately, tropical regions traditionally have been threatened by outbreaks of the toxic benthic dinoflagellate Gambierdiscus, which is associated with ciguatera fish poisoning. The ciguatoxins produced by Gambierdiscus bioaccumulate in reef fishes and are responsible for the most common algal toxin-related illnesses, globally affecting the greatest number of victims and often with significant long-term health effects. Recently, Gambierdiscus has been documented in subtropical and temperate latitudes. Blooms of another benthic and toxic dinoflagellate, Ostreopsis, have become more frequent and intense, especially in temperate waters. Ostreopsis produces palytoxins and analogues, and some outbreaks have been associated with massive benthic faunal damage and respiratory irritations in humans exposed to aerosols. The increased frequency of harmful events and the biogeographic extension of benthic microalgae incentivized the launch of the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB) Core Research Project on “Benthic Harmful Algal Blooms” in 2010. This article summarizes the main scientific advances and gaps in related knowledge as well as advances the project has made toward managing and mitigating the impacts of benthic HABs on human illnesses and marine resource losses.

In the framework of monitoring of benthic harmful algal blooms (BHABs), the most commonly reported sampling strategy is based on the collection of macrophytes. However, this methodology has some inherent problems. A potential alternative method uses artificial substrates that collect resuspended benthic cells. The current study defines main improvements in this technique, through the use of fiberglass screens during a bloom of Ostreopsis cf. ovata. A novel set-up for the deployment of artificial substrates in the field was tested, using an easy clip-in system that helped restrain substrates perpendicular to the water flow. An experiment was run in order to compare the cell collection efficiency of different mesh sizes of fiberglass screens and results suggested an optimal porosity of 1-3 mm. The present study goes further on showing artificial substrates, such as fiberglass screens, as efficient tools for the monitoring and mitigation of BHABs. (C) 2016 Elsevier Ltd. All rights reserved.

During the summer of 2010, 31 species including fish, echinoderms, gastropods, crustaceans, cephalopods and sponges were sampled in the Bay of Villefranche on the French Mediterranean coast and screened for the presence of PLTX-group toxins using the haemolytic assay. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for confirmatory purposes and to determine the toxin profile. The mean toxin concentration in the whole flesh of all sampled marine organisms, determined using the lower- (LB) and upper-bound (UB) approach was 4.3 and 5.1 µg·kg−1, respectively, with less than 1% of the results exceeding the European Food Safety Authority (EFSA) threshold of 30 µg·kg−1and the highest values being reported for sea urchins (107.6 and 108.0 µg·kg−1). Toxins accumulated almost exclusively in the digestive tube of the tested species, with the exception of octopus, in which there were detectable toxin amounts in the remaining tissues (RT). The mean toxin concentration in the RT of the sampled organisms (fishes, echinoderms and cephalopods) was 0.7 and 1.7 µg·kg−1 (LB and UB, respectively), with a maximum value of 19.9 µg·kg−1 for octopus RT. The herbivorous and omnivorous organisms were the most contaminated species, indicating that diet influences the contamination process, and the LC-MS/MS revealed that ovatoxin-a was the only toxin detected.

The marine dinoflagellate genus Ostreopsis includes species producing potent toxic compounds, such as paliytoxin and palytoxin analogs, which might cause problematic blooms in the Mediterranean Sea and other tropical or temperate areas. Phylogenetic and phylogeographical studies based on sequences of ribosomal genes, revealed the existence of distinct species and, within them, clades in relation to geographical distribution potentially representing new or cryptic species. The morphological variability of Ostreopsis complicates the identification of species; thus, molecular analyses of isolates or field samples can be helpful. The aim of this study was to improve the characterization of Ostreopsis species and investigate the geographical distribution by using large dataset composed of both new and old sampled isolates. To determine if mitochondrial genes can be used to identify Ostreopsis species, we designed new primers sets then amplified and sequenced representative regions of the COI (cytochrome c oxydase 1) and cob (cytochrome b) genes. Phylogenetic analyses of the resulting mitochondrial DNA (mtDNA) and existing or new ribosomal DNA (rDNA) sequence data showed little divergence in the mtDNA sequences among Ostreopsis species indicating that neither the COI or cob genes are phylogenetically informative. In contrast, the ribosomal gene phylogeny indicated the existence of distinct Ostreopsis species. A network of haplotypes (based on ITS-5.8S rDNA) inferred from O. cf. ovata isolates collected worldwide revealed that Atlantic/Mediterranean and Indo/Pacific areas might host two separated large populations. In conclusion, it appears that rDNA gene sequences provide an effective molecular means of distinguishing the phylogenetic and phylogeographical relationships among Ostreopsis species. (C) 2014 Elsevier B.V. All rights reserved.

Ostreopsis cf. ovata produces palytoxin analogues including ovatoxins (OVTXs) and a putative palytoxin (p-PLTX), which can accumulate in marine organisms and may possibly lead to food intoxication. However, purified ovatoxins are not widely available and their toxicities are still unknown. The aim of this study was to improve understanding of the ecophysiology of Ostreopsis cf. ovata and its toxin production as well as to optimize the purification process for ovatoxin. During Ostreopsis blooms in 2011 and 2012 in Villefranche-sur-Mer (France, NW Mediterranean Sea), microalgae epiphytic cells and marine organisms were collected and analyzed both by LC-MS/MS and hemolysis OPEN ACCESS Mar. Drugs 2014, 12 2852 assay. Results obtained with these two methods were comparable, suggesting ovatoxins have hemolytic properties. An average of 223 μg· kg −1 of palytoxin equivalent of whole flesh was found, thus exceeding the threshold of 30 μg· kg −1 in shellfish recommended by the European Food Safety Authority (EFSA). Ostreopsis cells showed the same toxin profile both in situ and in laboratory culture, with ovatoxin-a (OVTX-a) being the most abundant analogue (~50%), followed by OVTX-b (~15%), p-PLTX (12%), OVTX-d (8%), OVTX-c (5%) and OVTX-e (4%). Ostreopsis cf. ovata produced up to 2 g of biomass per L of culture, with a maximum concentration of 300 pg PLTX equivalent cell −1. Thus, an approximate amount of 10 mg of PLTX-group toxins may be produced with 10 L of this strain. Toxin extracts obtained from collected biomass were purified using different techniques such as liquid-liquid partition or size exclusion. Among these methods, open-column chromatography with Sephadex LH20 phase yielded the best results with a cleanup efficiency of 93% and recovery of about 85%, representing an increase of toxin percentage by 13 fold. Hence, this purification step should be incorporated into future isolation exercises.

In recent decades, the North West Mediterranean Sea has been seriously affected by the development of the toxic benthic dinoflagellate Ostreopsis cf. ovata, which is associated with harmful effects on human health and the environment. The present work aims to provide a large overview of the multiple environmental factors assumed to regulate or influence the growth of Ostreopsis. An intensive sampling campaign over a full annual cycle was performed along the French and Italian coasts (in six sites from Cassis to Genoa), to determine patterns of temporal and spatial distributions of both O. cf. ovata epiphytic and planktonic cells. Results highlighted substantial seasonal variations in the abundance of Ostreopsis. These variations correlated to seawater temperature, with an optimum growth temperature ranging from 23 degrees C to 27.5 degrees C. Phosphate concentration, rather than nitrogen or silicate, was also positively associated with Ostreopsis. Decreases in oxygen and increases in chlorophyll a concentrations were recorded during the summer blooming period. The maximal Ostreopsis epiphytic abundance was generally higher on Dictyota spp. than on the other two sampled macroalgae (up to 8.54 x 10(6) cells g(-1) FW), even though statistical analysis did not support a clear substrate preference. Epiphytic abundances were significantly higher at a very shallow depth (0.5 m), than at 1 and/or 3 m depths. High anthropogenic pressure (related to population density) seems to have promoted the occurrence of blooms in urbanized areas, which could partly explain the strong demarcation in Ostreopsis development between Western and Eastern sampling sites. The ecological niche of Ostreopsis cf. ovata needs precise definition, which will require further in situ and in vitro experimental studies, to determine the relative importance of distinct environmental parameters

Four sites located in Nice and Villefranche-sur-Mer, on the French Mediterranean coast, were monitored during the summer of 2009 for the presence of epiphytic and planktonic Ostreopsis cf. ovata, and that of palytoxin (PITX) and 2 of its analogues (ovatoxin-a (OVTX-a) and ostreocin-D (OST-D)) in different marine organisms. Several of the 15 species that were sampled between June and September 2009 were found to be contaminated with OVTX-a as the major toxin (90% of the toxin profile) and PITX; this included fish, echinoderms, gastropods, crustaceans and cephalopods. The contamination levels varied geographically and between species, with the herbivorous species generally having higher toxin levels than carnivorous ones. The determination of the toxin distribution between the digestive tube (DT) and the remaining tissue (RT) or roe in the case of the sea urchin Paracentrotus lividus showed that the toxins were sequestered in the DT. The highest toxin level ever recorded over the course of the study was of 392.2 mu g for the sum of OVTX-a and PITX per kg of DT of the flathead mullet Mugil cephalus. No quantifiable levels of toxins were found in the roe of the sea urchins or in the RT of the other marine products. However, in several cases, the toxin level in the whole flesh of the analysed organisms was above 30 mu g OVTX-a + PITX/kg, when knowing that the European food safety authority's opinion is that an adult should not ingest more than 30 mu g PITX + OST-D per kg of shellfish meat to avoid putting the consumer's health at risk. This was observed for the following four species: the sea urchin P. lividus, the red-mouthed rock shell Stramonita haemastoma, the warty crab Eriphia verrucosa and the flathead mullet M. cephalus. The collection of such data is of great importance to refine and complete the risk assessment of PITX and its analogues and has to be encouraged in order to provide reliable information for setting up a regulatory level that would protect the consumers of edible marine organisms (C) 2013 Elsevier B.V. All rights reserved.

Identification of dinoflagellates to specific level is sometimes arduous due to high diversity and frequent morphological variability. Focusing on Neoceratium genus, often used as ecological indicator, our collaborative web site provides to scientists an accessible and detailed taxonomic tool, allowing accurate identification of its numerous species and varieties. This original web site offers the possibility to visualize several taxa to avoid confusion between infraspecific taxa of the same species and between morphologically close taxa, belonging to different species.

The development of Ostreopsis cf. ovata, a toxic benthic dinoflagellate has increased in the North Western Mediterranean Sea, causing health, ecological and economical concerns. In order to understand the ecological impact on macroinvertebrates, a preliminary study was carried on edible grazers, the sea urchin Paracentrotus lividus and the limpet Patella spp. Their densities were followed toward the abundance of O. cf. ovata. Thus, in 2008, we performed a monthly field survey in scuba-diving in three sites of the North Western Mediterranean Sea (Genoa, Nice and Villefranche-sur-Mer) at the sea surface and at 1 and 3 m depth. Results showed that at 1 m and 3 m depth, the density of P. lividus was not clearly affected by a strong development of Ostreopsis. Decrease in P. lividus abundance may be due to natural variation or to fishing activities especially in France. Regarding the density of Patella spp., only one significant decrease was observed between July and August 2008 in Genoa. Patella species are living in the interdital zone, we could therefore hypothese that the limpets were intoxicated either by direct ingestion of O. cf ovata by grazing and/or by the toxins released in the surrounding water.

The main goal of the multidisciplinary MediOs project was to acquire and analyze pertinent scientific knowledge in fields as diverse as ecology, biology, chemistry, epidemiology or socio-economics concerning the occurrence of species belonging to genus Ostreopsis (toxic benthic dinoflagellates) in the Mediterranean. The economic impact of Ostreopsis was estimated, based on the intensity and frequency of blooms. Results obtained allowed science-based recommendations concerning the management of risk, with suggestions to optimize environmental surveys, to initiate a food risk survey, and to structure actions at the national level.

Ecologie du dinoflagellé benthique toxique Ostreopsis cf. ovata en Méditerranée Nord-Occidentale.

Dinoflagellates of the genus Ostreopsis are known to cause (often fatal) food poisoning in tropical coastal areas following the accumulation of palytoxin (PLTX) and/or its analogues (PLTX group) in crabs, sea urchins or fish. Ostreopsis spp. occurrence is presently increasing in the northern to north western Mediterranean Sea (Italy, Spain, Greece and France), probably in response to climate change. In France, Ostreopsis. cf. ovata has been associated with toxic events during summer 2006, at Morgiret, off the coast of Marseille, and a specific monitoring has been designed and implemented since 2007. Results from 2008 and 2009 showed that there is a real danger of human poisoning, as these demonstrated bioaccumulation of the PLTX group (PLTX and ovatoxin-a) in both filter-feeding bivalve molluscs (mussels) and herbivorous echinoderms (sea urchins). The total content accumulated in urchins reached 450 mu g PLTX eq/kg total flesh (summer 2008). In mussels, the maximum was 230 mu g eq PLTX/kg (summer 2009) compared with a maximum of 360 mu g found in sea urchins during the same period at the same site. This publication brings together scientific knowledge obtained about the summer development of Ostreopsis spp. in France during 2007, 2008 and 2009.

The tropical benthic dinoflagellate Ostreopsis cf. ovata recently occurred in the shallow coastal NW Mediterranean where blooms have caused health problems to humans. As part of the MediOs 2 project within the French research program Liteau III, we investigated the possible effects of this toxic microalga on the meiofauna (i.e. metazoans ranging from 40 mu m to 1 mm in size) inhabiting the very common brown macroalga Halopteris scoparia. The macroalga was sampled in triplicate at 0.5 m depth in six stations along the French and Italian coasts on seven occasions in 2008. Ostreopsis bloomed in summer in three out of the six stations with abundances ranging from 2.5 to 6.6 10(5) cells g(-1) macroalgal wet weight. Mean metazoan meiofauna densities ranged from 1274 to 9774 individuals g(-1) macroalgal spin-wet weight. Statistical analyses revealed that changes in the community structure were associated with high abundances of Ostreopsis. The most affected organisms were the nauplii suggesting a negative impact on harpacticoid copepod reproduction.

The presence of dinoflagellates of the genus Ostreopsis along Mediterranean coasts was first observed in 1972, in the bay of Villefranche-sur-Mer. However, over the past ten years, harmful events related to this benthic dinoflagellate have been reported in Italian, Spanish, Greek, French, Tunisian and Algerian coastal areas. In France, during a hot period in August 2006, cases of dermatitis and respiratory problems were registered in Marseille area. At that time, a link to the proliferation of Ostreopsis was highlighted for the first time in that area. A specific monitoring was designed and implemented in the summer 2007. Two strains of Ostreopsis cf. ovata, collected in 2008 from Villefranche-sur-Mer and Morgiret coastal waters and grown in culture, were identified by molecular analysis and studied to characterise their growth and toxin profile. Liquid chromatography-mass spectrometry (LC-MS/MS) indicated that both strains produced ovatoxin-a (OVTX-a) as the major component (ca. 90%), and traces of palytoxin (PLTX). Toxin content was determined at the end of the exponential growth phase with highest concentration of 55 pg.cell(-1) of OVTX-a and 2.5 pg.cell(-1) of PLTX.

Impact of Ostreopsis cf. ovata development on macroinvertebrates in the NW Mediterranean Sea.

The effect of Ostreopsis cf. ovata, a toxic benthic dinoflagellate, on phytal meiofauna from the coastal NW Mediterranean.

Impacts des facteurs environnementaux sur le développement d'Ostreopsis cf. ovata durant les étés 2007 et 2008 à Monaco (Méditerranée Nord-Occidentale).

The French research project MediOs 2 (Mediterranée Ostreopsis): Ecological aspects. International workshop "Blooms and invasions of marine species

Changes in marine phytoplankton communities at short-time scales have rarely been examined. As a part of the DYNAPROC 2 cruise (14 September-17 October 2004), conducted in the NW Mediterranean Sea, we daily sampled and determined taxonomic composition and abundance of the microphytoplankton and the dominant microzooplanktonic groups from both net and bottle sampling, during 4 cycles of 5 days. Hydrological conditions were characterised by the dominance of a stratified water column and nutrient-depleted conditions. However the stratification index revealed a destabilization of the water column from the beginning of the second cycle, related to a wind stress event accompanied with coastal water intrusion. This conducted to an increase of taxonomic richness and a general decrease of evenness, depicting the dominance of species with the best fitness. We also emphasised on the great interest of taxonomic studies, as able to provide valuable information on biogeochemical-important groups of species, potential water masses indicators and trophic aspects of the community that are ignored or largely underestimated with other kind of phytoplankton studies, such as pigment analysis.

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.

DEVELOPMENT OF THE BENTHIC TOXIC DINOFLAGELLATE OSTREOPSIS CF. OVATA IN THE NW MEDITERRANEAN SEA

To study environment characteristics favoring the toxic benthic dinoflagellate Ostreopsis cf. ovata, a survey was conducted in Monaco (NW Mediterranean Sea), in summers 2007 and 2008. Epiphytic and planktonic blooms occurred almost simultaneously and a high variation of abundances at low spatial scales was observed. An early and very marked bloom occurred in 2007, compared to a later and less abundant development in 2008. These distinct patterns in bloom timing corresponded with very different hydroclimatic scenarios in 2007 (hot spring and relatively cold summer) and 2008 (standard year compared to the median year profile estimated with data from 1995 to 2008). No clear impacts of summer seawater temperature, rainfall or nutrient concentrations were evident. Strong wind may favor the dispersal of benthic and planktonic cells. Our study suggests that further investigations are needed to examine the potential role of Ostreopsis nutritional mode (i.e. autotrophy vs. mixotrophy).

Ostreopsis cf. ovata development in relation with depth, biotic substrate and environmental factors in the North Western Mediterranean Sea in 2008 and 2009 years - MediOs 2 program.

Harmful benthic microalgae blooms represent an emergent phenomenon in temperate zones, causing health, ecological and economic concern. The main goal of this work is to compile records of Ostreopsis at large temporal and spatial scales, in order to study the relationship between cell abundances, the periodicity and intensity of the blooms and the role of sea water temperature in 14 Spanish, French, Monegasque and Italian sites located along the northern limits of the Mediterranean Sea. General trends are observed in the two considered basins: the north-western Mediterranean Sea, in which higher cell abundances are mostly recorded in mid-summer (end of July), and the northern Adriatic Sea where they occur in early fall (end of September). The sea water temperature does not seem to be a primary driver, and the maximal abundance periods were site and year specific. Such results represent an important step in the understanding of harmful benthic microalgae blooms in temperate areas, and provide a good base for managers in the attempt to monitor and forecast benthic harmful microalgae blooms.

Impact d'un dinoflagellé benthique toxique Ostreopsis cf. ovata sur l'abondance et la composition de la méiofaune des macroalgues en Méditerranée nord-occidentale.

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in the NW Mediterranean sea.

The French research project MediOs 2 (Mediterranée Ostreopsis) and the relations with managers and policy makers.

Impact of environmental factors on Ostreopsis cf. ovata dynamic during the summers 2007 and 2008 in Monaco (NW Mediterranean Sea).

Trends in Ostreopsis cf. ovata proliferation along the northern Mediterranean Sea (NW Mediterranean and Adriatic Seas) coastal waters.

Objective. Ostreopsis ovata and Ostreopsis siamensis are tropical unicellular algae that have been found recently in the Mediterranean. Both of these dinoflagellates produce palytoxin (PTX)-like toxins that are powerful vasoconstrictors in mammals. Since 2003, Ostreopsis blooms in Italy and Spain have been accompanied by reports of respiratory problems and skin/mucosa irritation in persons in contact with toxic microalgal cells (epiphytes, plankton, or sea spray) or associated toxins. Methods. In France, a surveillance network has been set up to monitor water conditions and to protect swimmers from contamination due to Ostreopsis. Results. Between 2006 and 2009, a total of nine blooms were observed on the French Mediterranean coast including five that led to manifestations in divers, swimmers, and shoreline inhabitants. A total of 47 patients presented symptoms of involving benign or mild skin, mucosal, and/or respiratory irritation that regressed spontaneously without treatment within 12-72 h (4-12 h with nonsteroidal anti-inflammatory drugs). During the study period, five beaches were temporarily closed. Discussion. In the Mediterranean, Ostreopsis blooms induce skin and respiratory disorders when human beings are exposed to saltwater with a high concentration of algal cells. However, palytoxin dosages carried out on the food chain (urchins, mussels) indicate that this risk of toxins accumulation in seafood must be taken into account and that the surveillance network should be upgraded accordingly.</.

Effet de la profondeur et du substrat sur le développement d'Ostreopsis cf. ovata.

Variabilité spatiale de l'abondance d'Ostreopsis cf. ovata épiphyte et libre (Baie de Villefranche‐sur‐mer, 2009).

Suivi du développement estival d'Ostreopsis spp. à Monaco en 2007 et 2008.

Etude écologique et génétique des populations d'un dinoflagellé benthique toxique, Ostreopsis cf. ovata, en Méditerranée Nord Occidentale.

Our knowledge of the response of phytoplankton to climate change is restricted by the lack of phytoplankton long-term studies, especially those reporting species data. To circumvent this problem, we combined recent data from sampling at monitoring sites with old bibliographic data. The study was conducted on the genus Ceratium (planktonic dinoflagellates) in the NW Mediterranean, as numerous studies have been conducted in the area since the beginning of the 20th century. In addition, species of this highly diverse genus are known to be particularly sensitive to water temperature, and should thus be responsive to global warming. The temporal distribution of Ceratium species over the last century showed a progressive disappearance from the surface layer of likely stenothermic species, which may have moved to deeper layers in response to water warming, along with a decrease of species richness during the annual cycle. Seasonal and phenological aspects of Ceratium assemblages were also affected, as illustrated by the earlier timing in the minimum of richness. A change in the overall species assemblage also occurred from past to present in the Ligurian Sea, suggesting a warming in this area consistent with the development in surface water temperatures. Our results suggest that Ceratium species may constitute good biological indicators of warming in the NW Mediterranean Sea. In addition, the present study showed the importance of time-series data and the value of historical literature as the basis for ecological studies of long-term trends needed to substantiate our current understanding of the impact of global change on marine biodiversity.

Influence du développement d'Ostreopsis spp. sur la macrofaune (oursins et patelles) durant l'année 2008.

Developpement of Ostreopsis spp. in monaco in relation with environmental factors.

Surveillance de la qualité des eaux de baignades : recherche et suivi du développement des dinoflagellés toxiques du genre Ostreopsis au niveau du littoral de Monaco. Eté 2009.

We describe remarkable diurnal changes in the morphology of the planktonic dinoflagellate Ceratium ranipes. The species is distinguished by the unusual appendages, known as toes or fingers, protruding from its horns. Varieties have been described based on the characteristics of the fingers. We discovered that cultures, maintained on a 12:12 photoperiod, when examined during the dark period were composed of `finger-less' cells. Monitoring of isolated cells revealed a diurnal cycle of distinct changes in morphology with daytime cells showing appendages, well-stocked with chlorophyll, and the absence of the fingers at the end of the photoperiod. Fingers are absorbed at the end of the light period and re-grown at the end of the dark period. Sampling the Bay of Villefranche, we found the distinct morphologies in a natural population at night and during the day. & 2009 Elsevier GmbH. All rights reserved.

Marine phytoplankton organisms account for more than 45% of the photosynthetic net primary production on Earth. They are distributed across many of the major clades of the tree of life and include prokaryotes, and eukaryotes that acquired photosynthesis through the process of endosymbiosis. If the number of extant described species is relatively low compared to the diversity of the terrestrial plants, recent insights into the genetic diversity of natural assemblages have revealed a large unsuspected diversity at different taxonomic levels. Wide infra-specific diversity is also being discovered in many widespread and well known morphological species. This review summarizes data obtained in the fields of ecology, evolutionary biology, physiology and genomics that have improved our understanding of the biodiversity and evolution of marine phytoplankton. To cite this article: N. Simon et al., C R. Biologies 332 (2009). (C) 2008 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Évolution d'Ostreopsis ovata dans la Baie de Villefranche en 2009 & Suivi à haute fréquence aux Marinières.

Étude des TEP et des bactéries associées à Ostreopsis cf. ovata.

Dynamics of Ostreopsis cf. ovata in the Mediterranean Sea, relations with environmental factors and consequences on shallow rocky ecosystems.

Microflore associée à Ostreopsis cf. ovata entre Cassis et Gênes durant l'année 2008.

DEVELOPMENT OF THE BENTHIC TOXIC DINOFLAGELLATE OSTREOPSIS CF. OVATA IN MONACO (NW MEDITERRANEAN SEA)

Le développement de la microflore benthique (dont Ostreopsis spp.) durant l'année 2008 au niveau de 6 stations entre Cassis (France) et Gênes (Italie).

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in Monaco (NW Mediterranean sea).

Évolution d'Ostreopsis cf. ovata épiphyte et planctonique en 2008 entre Cassis et Gênes en fonction de la profondeur, de la température et de la concentration en sels nutritifs.

Les dinoflagellés toxiques du genre Ostreopsis en Méditerranée Nord-Occidentale

Le développement d'Ostreopsis cf. ovata à Monaco en 2007 et 2008.

Le développement des dinoflagellés toxiques benthiques du genre Ostreopsis en Méditerranée NO : présentation du projet MediOs 2.

Les dinoflagellés toxiques du genre Ostreopsis en Méditerranée Nord Occidentale.

Développement d'Ostreopsis cf. ovata à Monaco en 2007 et 2008 : influence des paramètres physico-chimiques.

La surveillance " Ostreopsis " mise en place par l'Observatoire de Villefranche et l'Université de Nice durant l'été 2008 pour répondre aux besoins du Ministère de la Santé (Côte d'Azur et Var).

Surveillance de la qualité des euax de baignades : recherche et suivi du développement des dinoflagellés toxiques du genre Ostreopsis au niveau du littoral de Monaco. Eté 2008.

Toxic harmful algal bloom (HAB) occurrence is becoming more frequent and problematic in highly urbanized coastal zones. In summer 2005 along the urbanized Genoa coastline (Ligurian Sea, North western Mediterranean Sea), local first aid stations treated about 200 people, who all showed similar symptoms following exposure to marine aerosols. The link with proliferation of Ostreopsis ovata was made, and it highlighted for the first time, the risks that benthic HABs may represent in highly urbanised temperate areas. Subsequently, a specific monitoring plan was designed and implemented in the same area in July 2006, before the first signs of Ostreopsis proliferation were detected. Here we report on this quantification of an Ostreapsis ovata bloom in the Ligurian Sea. Cells were quantified both in the water column and in the epiphytic community on macrophytes. Our results suggest a role of sea water temperature and weather conditions in favouring bloom development. (c) 2008 Elsevier Ltd. All rights reserved.

Surveillance de la qualité des eaux de baignade : recherche et suivi du développement des dinoflagellés toxiques du genre Ostreopsis au niveau du littoral de Monaco

In diversity research, the use of survey data appears to have declined in favour of experimental or modeling approaches because direct relationships are difficult to demonstrate. Here we show that use of field data can yield information concerning the mechanisms governing diversity. First, we establish that tintinnids display a global latitudinal pattern of diversity similar to other pelagic organisms; species numbers appear to peak between 20 degrees and 30 degrees north or south. This common large scale spatial trend has been attributed to the gradient in water column structure across the global ocean. We then examine the generality of a relationship between planktonic diversity and water column structure by considering data from the Mediterranean Sea, in which water column structure changes seasonally. Among populations of foraminifera, tintinnids, and the dinoflagellates of the genus Ceratium, we compare data from trans-Mediterranean sampling conducted at different times and monthly changes in species richness at single sites. We find that water column structure alone appears to be a poor predictor of temporal changes in diversity. Lastly, we present an example of temporal changes in tintinnid diversity based on data from an oceanographic sampling station in the N. W. Mediterranean where resources, as chlorophyll, appear distinctly unrelated to changes in water column structure. We show that short-tem temporal changes in diversity (week to week shifts) can be related to changes in chlorophyll concentration. We conclude that in tintinnids diversity can be directly linked to characteristics of food resources.

Seasonal abundance, volume, size distribution and carbon content of transparent exopolymeric particles (TEP) were examined in 2 hydrologically distinct sites in the NW Mediterranean (NWM) Sea: a coastal (Point B, Villefranche Bay) and an offshore (DYFAMED, France, JGOFS) site. TEP concentration varied from 0.2 to 2.2 x 10(5) particles ml(-1), and was higher offshore. The TEP pool was low during the winter mesotrophic period and increased after the spring bloom, remaining relatively high throughout summer at both sites. The increase in TEP abundance during the oligotrophic period was relatable to nitrate limitation and a decline in primary production. TEP formation in spring was associated to a nanoflagellate bloom, while the build-up of a large pool of TEP in summer occurred in the presence of a phytoplankton community dominated by picoplankters and during strong thermal stratification, limiting vertical sedimentation. In the NWM Sea, when the TEP carbon pool (TEP-C) is high, it may represent up to 22% of the total organic carbon, and reach down to 1% when it is low, suggesting that the particles play a significant role in the carbon cycle. In the NWM Sea, the trophic status of the system and the composition of primary producers control TEP formation. Hydrological processes appear to be of primary importance in governing seasonal TEP distribution.

Planktonic microbial communities often appear stable over periods of days and thus tight links are assumed to exist between different functional groups (i.e. producers and consumers). We examined these links by characterizing short-term temporal correspondences in the concentrations and activities of microbial groups sampled from 1 m depth, at a coastal site of the N.W. Mediterranean Sea, in September 2001 every 3 h for 3 days. We estimated the abundance and activity rates of the autotrophic prokaryote Synechococcus, heterotrophic bacteria, viruses, heterotrophic nanoflagellates, as well as dissolved organic carbon concentrations. We found that Synechococcus, heterotrophic bacteria, and viruses displayed distinct patterns. Synechococcus abundance was greatest at midnight and lowest at 21:00 and showed the common pattern of an early evening maximum in dividing cells. In contrast, viral concentrations were minimal at midnight and maximal at 18:00. Viral infection of heterotrophic bacteria was rare (0.5-2.5%) and appeared to peak at 03:00. Heterotrophic bacteria, as % eubacteria-positive cells, peaked at midday, appearing loosely related to relative changes in dissolved organic carbon concentration. Bacterial production as assessed by leucine incorporation showed no consistent temporal pattern but could be related to shifts in the grazing rates of heterotrophic nanoflagellates and viral infection rates. Estimates of virus-induced mortality of heterotrophic bacteria, based on infection frequencies, were only about 10% of cell production. Overall, the dynamics of viruses appeared more closely related to Synechococcus than to heterotrophic bacteria. Thus, we found weak links between dissolved organic carbon concentration, or grazing, and bacterial activity, a possibly strong link between Synechococcus and viruses, and a missing link between light and viruses.

Filter-feeding larvae of the sea urchin Paracentrotus lividus fed phytoplankton previously exposed to sublethal amounts of toxins were chosen as a model to assess the potential effects of natural toxins on survivorship, development and feeding behaviour. The marine microalga Cricosphaera elongata was incubated with organic extract of the green seaweed Caulerpa taxifolia and then offered to larvae at different stages of development. Sensitivity to the toxin-treated food depended on the larval stage at which exposure began. Larvae reared from first feeding (4-arm stage) with toxin-treated microalgae were most sensitive (25% survival, delay in development and a metamorphosis rate of 32%). A diet begun at the 8-arm stage caused a decrease in survival and abnormal development; however, all the remaining larvae achieved metamorphosis. Certain ontogenic stages were more sensitive than others; in all treatments, mortality rate was highest during the formation of the echinus rudiment. Feeding experiments comparing ingestion of inert and toxin-treated polystyrene microspheres suggested that larvae discriminate against toxin-treated particles. (C) 1999 Elsevier Science Ltd. All rights reserved.

The spectacular development of the green alga Caulerpa taxifolia (Vahl) C. Agardh, introduced in the Mediterranean in 1984, represents a biological pollution which threatens the biodiversity of the marine ecosystem. The weak pressure from grazers and the presence of repulsive secondary metabolites make the problem worse. Whereas the anti-appetant effect of these metabolites is well known, their role in competition between algae has not been extensively studied. Using a microalgal model representing the initial stage of the marine food chain, we studied the effects of C. taxifolia metabolites. We showed that organic extracts of C. taxifolia and caulerpenyne inhibit or delay the proliferation of several phytoplanktonic strains to various degrees. Seasonal variations of the toxicity were observed with a maximal effect in the summer. Experiments with Dunaliella minuta showed that caulerpenyne did not affect the protein content but strongly reduced that of the cell chlorophyll A.

Caulerpenyne (CYN), the major metabolite synthesized by the alga Caulerpa taxifolia (Vahl), inhibited the first cleavage of sea urchin eggs without affecting fertilization. The effect was dose-dependent with a half maximal dose of 33 mu M. Blockage of cleavage was observed when the toxin miss added within 40 min of insemination. A preliminary search for the cellular targets of this toxin showed that ionic signals involved in the cell dynamics are altered: caulerpenyne reduced the intracellular ATP-dependent Ca2+ accumulation in a dose-dependent manner but did not provoke a release of sequestered Ca2+. This effect is similar to that of thapsigargin, a specific inhibitor of reticular Ca2+-ATPase. CYN had no effect on the incorporation of S-35-methionine into proteins. H-3-thymidine incorporation into DNA was inhibited by CYN in a dose-dependent manner: an effect well correlated with cell division kinetics. A CYN concentration of 30 mu M, which delayed the first cleavage, inhibited overall protein phosphorylation but did not affect histone kinase phosphorylating activity. Thus, CYN appears to alter the main events of sea urchin egg cleavage, and may therefore constitute an ecological risk for microorganisms and eggs of pluricellular animals living close to these algae. Moreover, this compound is of potential pharmacological interest in view of its antiproliferative properties.

Caulerpa taxifolia (Vahl) C. Agardh (Ulvophyceae, Caulerpales) is an alga of tropical origin that was accidentally introduced into the Mediterranean sea in 1984, where this species can reach an abundance that has never been described in tropical endemic regions. It is known that caulerpacean algae can develop an efficient strategy against grazers consisting of the synthesis of repulsive of toxic secondary metabolites: we report here the first study of the toxicity of purified secondary metabolites and raw extracts from C. taxifolia from the Mediterranean. Toxicity was evaluated on three models: mice (lethality), mammalian cells in culture (cytotoxicity) and sea urchin eggs (disturbance of cell proliferation). Aqueous extracts are only active on fibroblasts and mice. In the three toxicity models a seasonal variation of toxicity is observed for the crude methanol extract as well as a decrease of this activity when C. taxifolia from the Mediterranean is kept in aquaria. Pure compounds exhibit different toxicity depending on the assay. 10,11-epoxycaulerpenyne is the most active substance on mice and fibroblasts whereas taxifolial A and D are inactive or only weakly toxic. Among the four tested compounds caulerpenyne, the major metabolite of C. taxifolia, is the most active on sea urchin eggs. Caulerpenyne may therefore represent an ecological risk for microorganisms and the eggs of multicellular animals living close to this alga. The ecological impact of this toxicity on marine organisms and the interaction of this alga with the herbivorous fauna are discussed