Modelling paralytic shellfish toxins (PST) accumulation in Crassostrea gigas by using Dynamic Energy Budgets (DEB)

As other filter-feeders, Crassostrea gigas can concentrate paralytic shellfish toxins (PST) by consuming dinoflagellate phytoplankton species like Alexandrium minutum. Intake of PST in oyster tissues mainly results from feeding processes, i.e. clearance rate, pre-ingestive sorting and ingestion that are directly influenced by environmental conditions (trophic sources, temperature). This study aimed to develop a mechanistic model coupling the kinetics of PST accumulation and bioenergetics in C. gigas based on Dynamic Energy Budget (DEB) theory. For the first time, the Synthesizing Units (SU) concept was applied to formalize the feeding preference of oysters between non-toxic and toxic microalgae. Toxin intake and accumulation were both dependent on the physiological status of oysters. The accumulation was modelled through the dynamics of two toxin compartments: (1) a compartment of ingested but non-assimilated toxins, with labile toxins within the digestive gland eliminated via faeces production; (2) a compartment of assimilated toxins with a rapid detoxification rate (within a few days). Firstly, the DEB-PST model was calibrated using data from two laboratory experiments where oysters have been exposed to A. minutum. Secondly, it was validated using data from another laboratory experiment and from three field surveys carried out in the Bay of Brest (France) from 2012 to 2014. To account for the variability in PST content of A. minutum cells, the saxitoxin (STX) amount per energy units in a toxic algae (ρPST) was adjusted for each dataset. Additionally, the effects of PST on the oyster bioenergetics were calibrated during the first laboratory experiment. However, these effects were shown to depend on the strain of A. minutum. Results of this study could be of great importance for monitoring agencies and decision makers to identify risky conditions (e.g. production areas, seawater temperature), to properly assess detoxification step (e.g. duration, modalities) before any commercialization or to improve predictions regarding closing of shellfish areas

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Les microplastiques et leurs additifs dans les produits de la pêche : développements méthodologiques et prévalence

Increase in plastic production since the 1950's in combination with plastic waste mismanagement lead to the presence of plastic particle in terrestrial and marine environment. Plastic particles measuring less than 5 mm, called microplastics, are ingested by a wide range of organisms. The goal of this PhD thesis was to evaluate the microplastic hazard for seafood consumers. firstly, method for digesting seafood tissue without degrading plastic polymer was selected and applications limits were determined for digestion of fish digestive tracts. Concurrently, a Pyrolysis-GC/MS method was optimized, limit of detection were determined and this method was applied on environmental samples. Both methods were used to study microplastics contamination in bivalve and fish species used for human consumption. Bivalve contamination was between 0.15 and 0.74 MP/g of tissue wet weight whereas contaminations in fish were low. Indeed, digestive tracts were contaminated by in mean 0.01 MP/g of tissue wet weight and muscles were contaminated by in mean 0.001 MP/g of tissue wet weight. Lately, leaching of a plastic additive was studied using an in vitro enzymatic model of digestion. However, such phenomenon was not highlighted. Overall, these results will help to standardize the study of microplastics in seafood products.L'augmentation de la production de matière plastique depuis les années 1950 combinée à une mauvaise gestion des déchets plastiques ainsi qu'aux mauvais comportements des citoyens conduit à la contamination des écosystèmes terrestres comme marins. L'ingestion par des organismes marins de particules plastiques mesurant moins de 5 mm, appelées microplastiques, a été décrite. L'objectif de ces travaux de thèse était d'évaluer le danger "microplastique" pour le consommateur de produits de la pêche. Afin de répondre à cet objectif, la sélection et la caractérisation d'une méthode permettant de digérer les tissus des produits de la pêche a été. En parallèle, une méthode de Pyrolyse-GC/MS a été optimisée afin d'identifier les microplastiques les plus petits possibles. Ses limites d'applications ont été calculées puis la méthode a été appliquée sur des microplastiques provenant de différents produits de la pêche. Ces deux méthodes ont été appliquées dans la recherche de microplastiques dans deux espèces de bivalves et trois espèces de poissons. Pour les bivalves, la contamination aux microplastiques était comprise entre 0.15 et 0.74 MP/g de chair humide alors que pour les poissons la contamination était assez faible : 0,01 MP/g de tractus gastro-intestinal et 0,001 MP/g de filet. Pour finir, une étude exploratoire de la lixiviation d'un additif plastique en utilisant un modèle de digestion in vitro a été entreprise. Globalement, ces travaux de thèse permettent de proposer des voies d'harmonisation des méthodes pour l'étude des microplastiques dans les produits de la pêche pour, in fine, évaluer le danger pour le consommateur

Microplastics and their additives in seafood products : methodological developments and prevalence

L'augmentation de la production de matière plastique depuis les années 1950 combinée à une mauvaise gestion des déchets plastiques ainsi qu'aux mauvais comportements des citoyens conduit à la contamination des écosystèmes terrestres comme marins. L'ingestion par des organismes marins de particules plastiques mesurant moins de 5 mm, appelées microplastiques, a été décrite. L'objectif de ces travaux de thèse était d'évaluer le danger "microplastique" pour le consommateur de produits de la pêche. Afin de répondre à cet objectif, la sélection et la caractérisation d'une méthode permettant de digérer les tissus des produits de la pêche a été. En parallèle, une méthode de Pyrolyse-GC/MS a été optimisée afin d'identifier les microplastiques les plus petits possibles. Ses limites d'applications ont été calculées puis la méthode a été appliquée sur des microplastiques provenant de différents produits de la pêche. Ces deux méthodes ont été appliquées dans la recherche de microplastiques dans deux espèces de bivalves et trois espèces de poissons. Pour les bivalves, la contamination aux microplastiques était comprise entre 0.15 et 0.74 MP/g de chair humide alors que pour les poissons la contamination était assez faible : 0,01 MP/g de tractus gastro-intestinal et 0,001 MP/g de filet. Pour finir, une étude exploratoire de la lixiviation d'un additif plastique en utilisant un modèle de digestion in vitro a été entreprise. Globalement, ces travaux de thèse permettent de proposer des voies d'harmonisation des méthodes pour l'étude des microplastiques dans les produits de la pêche pour, in fine, évaluer le danger pour le consommateur.Increase in plastic production since the 1950's in combination with plastic waste mismanagement lead to the presence of plastic particle in terrestrial and marine environment. Plastic particles measuring less than 5 mm, called microplastics, are ingested by a wide range of organisms. The goal of this PhD thesis was to evaluate the microplastic hazard for seafood consumers. firstly, method for digesting seafood tissue without degrading plastic polymer was selected and applications limits were determined for digestion of fish digestive tracts. Concurrently, a Pyrolysis-GC/MS method was optimized, limit of detection were determined and this method was applied on environmental samples. Both methods were used to study microplastics contamination in bivalve and fish species used for human consumption. Bivalve contamination was between 0.15 and 0.74 MP/g of tissue wet weight whereas contaminations in fish were low. Indeed, digestive tracts were contaminated by in mean 0.01 MP/g of tissue wet weight and muscles were contaminated by in mean 0.001 MP/g of tissue wet weight. Lately, leaching of a plastic additive was studied using an in vitro enzymatic model of digestion. However, such phenomenon was not highlighted. Overall, these results will help to standardize the study of microplastics in seafood products

Isolation and Extraction of Microplastics from Environmental Samples: An Evaluation of Practical Approaches and Recommendations for Further Harmonisation

Researchers have been identifying microplastics in environmental samples dating back to the 1970s. Today, microplastics are a recognized environmental pollutant attracting a large amount of public and government attention, and in the last few years the number of scientific publications has grown exponentially. An underlying theme within this research field is to achieve a consensus for adopting a set of appropriate procedures to accurately identify and quantify microplastics within diverse matrices. These methods should then be harmonized to produce quantifiable data that is reproducible and comparable around the world. In addition, clear and concise guidelines for standard analytical protocols should be made available to researchers. In keeping with the theme of this special issue the goals of this focal point review are to provide researchers with an overview of approaches to isolate and extract microplastics from different matrices, highlight associated methodological constraints and the necessary steps for conducting procedural controls and quality assurance. Simple samples, including water and sediments with low organic content, can be filtered and sieved. Stepwise procedures require density separation or digestion before filtration. Finally, complex matrices require more extensive steps with both digestion and density adjustments to assist plastic isolation. Implementing appropriate methods with a harmonised approach from sample collection to data analysis will allow comparisons across the research community.acceptedVersio

Current frontiers and recommendations for the study of microplastics in seafood

International audienceFor seventy years, mass plastic production and waste mismanagement have resulted in huge pollution of the environment, including the marine environment. The first mention of seafood contaminated by microplastics was recorded in the seventies, and to date numerous studies have been carried out on shellfish, fish and crustaceans. Based on an ad hoc corpus, the current review aims to report on the numerous practices and methodologies described so far. By examining multiple aspects including problems related to the definition of the term microplastic, contamination at the laboratory scale, sampling and isolation, and quantification and identification, the aim was to point out current limitations and the needs to improve and harmonise practices for future studies on microplastics in seafood. A final part is devoted to the minimum information for publication of microplastics studies (MIMS). Based on the aspects discussed, MIMS act as a starting point for harmonisation of analyses

Isolation and Extraction of Microplastics from Environmental Samples: An Evaluation of Practical Approaches and Recommendations for Further Harmonisation

Researchers have been identifying microplastics in environmental samples dating back to the 1970s. Today, microplastics are a recognized environmental pollutant attracting a large amount of public and government attention, and in the last few years the number of scientific publications has grown exponentially. An underlying theme within this research field is to achieve a consensus for adopting a set of appropriate procedures to accurately identify and quantify microplastics within diverse matrices. These methods should then be harmonized to produce quantifiable data that is reproducible and comparable around the world. In addition, clear and concise guidelines for standard analytical protocols should be made available to researchers. In keeping with the theme of this special issue the goals of this focal point review are to provide researchers with an overview of approaches to isolate and extract microplastics from different matrices, highlight associated methodological constraints and the necessary steps for conducting procedural controls and quality assurance. Simple samples, including water and sediments with low organic content, can be filtered and sieved. Stepwise procedures require density separation or digestion before filtration. Finally, complex matrices require more extensive steps with both digestion and density adjustments to assist plastic isolation. Implementing appropriate methods with a harmonised approach from sample collection to data analysis will allow comparisons across the research community

Impacts of Altered Hydrology on the Sources of Particulate Organic Carbon on the Diet of Crassostrea Virginica in the Northern Everglades, Florida, Usa

WOS:000419555700020Stable isotope composition of the eastern oyster Crassostrea virginica was characterized from three estuaries in the Ten Thousand Islands (Florida). Freshwater inflow from watershed management is affecting this region and has deeply modified the salinity gradient. Stable carbon and nitrogen isotopes were used to trace specific sources of organic matter and the influence of these sources of carbon on the diet of the eastern oyster in the Greater Everglades. Oysters, as well as particulate organic matter (POM) and benthic microalgae (BMA) were sampled in three bays at three different stations from upstream to downstream during both wet and dry seasons. Significant salinity differences were observed in all estuaries between summer (wet) and winter (dry) seasons and were linked to freshwater inputs into the bays. Temperature followed a typical seasonal trend. Oysters were enriched in delta N-15 compared with POM and BMA, and similarly or slightly enriched in delta C-13 for both seasons. Lighter delta C-13 values in the upper stations in the estuaries suggest input of organic matter from terrestrial sources. Stable isotopes showed that oysters fed more on POM than on BMA. Condition index of oysters varied between stations and seasons in the three estuaries. Because the quality of organic matter consumed by oysters ultimately impacts the health of the oyster, changes in water quality and quantity of freshwater entering estuaries will have implications for future management of the habitat for this ecologically and economically important species

Etudes des microplastiques appliquées à la sécurité sanitaire des produits de la pêche

International audienceLes plastiques ainsi que leurs produits de dégradation comme les microplastiques (MPs) sont présents en quantités importantes dans les Océans. Si les conséquences des MPs sur l’environnement et le biote sont de plus en plus documentées, en revanche peu d’études concernent les organismes aquatiques en tant qu’aliment. Nos recherches portent sur l’impact des MPs sur la sécurité sanitaire des produits de la pêche.Afin de pouvoir réaliser des études comparables, des modes opératoires uniformisés sont nécessaires. Ainsi lors d’une première étude, nous avons cherché à sélectionner parmi un ensemble de protocoles issus de la littérature, celui permettant d’extraire puis d’identifier un maximum de polymères plastiques. La méthode retenue utilise une solution d’hydroxyde de potassium 10% pendant 24H à 60°C. Elle a permis de digérer des échantillons de produits de la mer tout en s’assurant que 14 des 15 types de polymères testés ne sont pas dégradés par la méthode.Parallèlement à cette partie récupération des MPs, des travaux ont été menés en terme d’identification des polymères plastiques par une approche de pyrolyse couplée à un chromatographe en phase gaz et un spectromètre de masse (Py-GC/MS). Cette méthode a fait l’objet d’une validation : estimation de la limite de détection, tests de répétabilité et de reproductibilité. Cette technique pourrait être appliquée en complément d’autres techniques d’identification comme la microspectrométrie Raman ou le FT-IR pour identifier des particules de petite taille comme les fibres ou encore les “pigments”.Par ailleurs, la Py-GC/MS sous réserve d’appliquer des températures de pyrolyse faibles (<100°C) serait également capable de détecter la présence d’additifs dans les polymères. Dans le cadre de cette thématique, un modèle digestif in vitro a été développé pour le poisson et l’Homme. L’application de cet outil à des polymères contenant différents additifs permettra d’évaluer la possibilité d’un relargage de produits chimiques dans le chyme

Occurrence and effects of plastic additives on marine environments and organisms: a review

International audiencePlastics debris, especially microplastics, have been found worldwide in all marine compartments. Much research has been carried out on adsorbed pollutants on plastic pieces and hydrophobic organic compounds (HOC) associated with microplastics. However, only a few studies have focused on plastic additives. These chemicals are incorporated into plastics from which they can leach out as most of them are not chemically bound. As a consequence of plastic accumulation and fragmentation in oceans, plastic additives could represent an increasing ecotoxicological risk for marine organisms. The present work reviewed the main class of plastic additives identified in the literature, their occurrence in the marineenvironment, as well as their effects on and transfers to marine organisms. This work identified polybrominated diphenyl ethers (PBDE), phthalates, nonylphenols (NP), bisphenol A (BPA) and antioxidants as the most common plastic additives found in marine environments. Moreover, transfer of these plastic additives to marine organisms has been demonstrated both in laboratory and field studies. Upcoming research focusing on the toxicity of microplastics should include these plastic additives as potential hazards for marine organisms, and a greater focus on the transport and fate of plastic additives is now required considering that these chemicals may easily leach out from plastics