From the characterization of factors determining paralytic toxin (PST) accumulation by the oyster Crassostrea gigas to risk assessment for human health within its social context – ACCUTOX

Harmful Algal Blooms (HABs) have major socio-economic and ecological impacts, by making the cultivated and/or fished shellfish unsuitable for consumption, by disrupting the balance of populations, by causing mortality or recruitment failures, and deeply disturbing human activities profoundly linked, directly or indirectly, to the shellfish industry.
In France, the dinoflagellates Alexandrium minutum and A. catenella, algal vectors of Paralytic Shellfish Toxins (PSTs) are regularly detected on the coastline and may contaminate the oyster production. PSTs accumulate into oysters and can become deadly to consumers at high doses. Accumulation of toxins appears variable between individual, reaching a factor of 80 between two oysters, suggesting variability in PST tolerance (Haberkorn et al. 2011*).
This project has for primary objective to better describe and understand the determinism of accumulation of PSTs in oysters. Two non-exclusive hypotheses will be tested: accumulation of PSTs depends on i) the tolerance of oysters, possibly related to polymorphism at voltage-gated sodium channels (target of PSTs), ii) the oyster physiological status. To assess the second hypothesis, an integrative approach, covering from molecular and cellular aspects to the whole organism, will be then developed on both diploid and triploid oysters as toxin burden was shown to be higher in triploid oysters than in diploid oysters during reproduction season (spring-summer) (Haberkorn et al. 2010a*; Guéguen et al., 2012*).
In a second step, an integrative model of toxin accumulation and detoxification will be developed taking into account the physiological parameters of the oysters contributing to a better assessment of toxin kinetics in oysters and associated risks. Then, individual variability of oyster contamination, physiological status and ploidy as well as variability of human consumption and uncertainty inherent to human dose-response will be taken into account for a quantitative risk assessment of health risks associated with toxic episodes and for analysis of different risk management strategies. However, the uncertainties inherent in scientific risk assessment related to contaminated oysters cannot be disconnected from its social, political and legal issues. To document the sources of social confusion and political tensions and controversies that regularly feed in this industrial sector, the social representations regarding the production and consumption of oysters will also be scientifically evaluated in this project.
Finally, a large outreach approach will be developed to better inform the public, professionals and stake holders about the issue of HABs and their impacts on bivalve toxicity.
Approaches and methodologies proposed here in their scientific, health, social and legal contexts will be beneficial to other phycotoxins and shellfish species and also to other biological (viruses and bacteria pathogenic to humans) and chemical (heavy metals, pesticides,...) contaminants.