TOUCAN (2016-2018)
TOUCAN project was coordinated by the laboratory of Ecotoxicology from Ifremer in Nantes (Dr F. Akcha). It was realized thanks to the collaboration of Ifremer research Unit CCEM (ex LEX and LBCM) and Laboratoire Environnement Ressources Arcachon (LERAR) and different teams of UMR EPOC (LPTC, EA, ECOBIOC). The project started in September 2016 for 2 years. It received 182000€ from the Labex COTE and funds for a post-doctorate contract by Ifremer.
TOUCAN proposed first a multidisciplinary approach for a better knowledge on the occurrence, distribution and fate of major chemical pollutants in Arcachon Basin and their trophic transfer and toxic effects, considering both historic (PAHs, copper) and emerging pollutants (pesticides, UV-filters). For each type of pollutants, the latest analytical chemistry methods were used to complete existing data for sediment, water column (dissolved phase and particulate organic matter (POM)) and transplanted oyster and in order to acquire new and original data concerning the contamination level of marine phytoplankton, potential vector of trophic contamination. Seawater and oyster tissue were also characterized by the determination of C and N elemental and isotopic ratios, such as C-to-chlorophyll a ratio in water. These analyses allowed to qualify and quantify the contribution of the different sources of organic matter to the pool of POM constituting oyster diet.
Secondly, to better assess the mechanisms involved in the trophic transfer of pollutants and their toxicity, an experimental approach was also developed during the project at the regional innovation platform of Bouin. Considering phytoplankton and oyster as primary producer and consumer respectively, the trophic transfer was studied for copper and the UV-filter octocrylene.
Some results are presented below focusing on copper. Due to new usages and sources, its concentrations are increasing in the Arcachon Basin, an important shellfish production area in France.
Field approach:
In Arcachon Bassin, we demonstrated that oysters near the continental shore are exposed over the year to higher loads of sediment particles and to higher metal contents in dissolved and particulate seawater phases. At the end of the 12-month long transplantation period, the oysters’ Cu body burdens had increased, and was shifted toward more positive δ65Cu values. The gradient of Cu isotope compositions observed was consistent with relative geographic distance and exposure intensities to unknown continental Cu sources. A binary isotope mixing model based on experimental data allowed to estimate the Cu continental fraction bioaccumulated in the transplanted oysters. The positive δ65Cu values and high bioaccumulated levels of Cu in transplanted oysters support that continental emissions are dominantly anthropogenic. While fluvial inputs and continental/urban run-off are suspected sources of metals of anthropogenic inputs in the bassin, sediment resuspension could be the main reason of metal release and contamination. The seagrass beds’ decline in the last two decades in the bay could have decreased the retention of fine particles in bottom sedimentary stratum. Oysters presenting the higher metal concentrations were those with the lower growth rates compared to oysters collected farther from the coast.
Experimental approach:
The trophic transfer of Cu was studied between a microalga, Tetraselmis suecica, and Crassostrea gigas spat and toxicity was assessed on both biota. Exposure of microalgal cultures to Cu for 7–8 days (3.1 ± 0.1, 15.7 ± 0.2 and 50.4 ± 1.0 µg Cu.L-1 for the control, Cu15 and Cu50 conditions, respectively) led to concentrations in microalgae (28.3 ± 0.9 and 110.7 ± 11.9 mg Cu.kg dry weight-1 for Cu15 and Cu50, respectively) close to those measured in the field. Exposed cultures could only be discriminated from controls by a higher relative content in intracellular reactive oxygen species, and a lower relative content in lipids together with a reduced metabolic activity. By contrast, the fatty acid profile of microalgae was modified, with a particularly relevant lower content of the essential polyunsaturated fatty acid 22:6n-3 (docosahexaenoic acid [DHA]). Following 21 days of spat feeding with Cu15 and Cu50 microalgal cultures, trophic transfer of Cu was observed with a high initial Cu concentration in spat tissues. Cu exposure was responsible for a decrease in the spat condition index, an outcome that could be related to an insufficient DHA supply and extra energy demand as suggested by the overexpression of genes involved in energy metabolism, ATP synthesis and glycogen catabolism.
For more information, please contact: Farida.Akcha@ifremer.fr
Associated articles:
Akcha Farida, Coquillé Nathalie, Sussarellu Rossana, Rouxel Julien, Chouvelon Tiphaine, Gonzalez Patrick, Legeay Alexia, Bruzac Sandrine, Sireau Teddy, Gonzalez Jean-Louis, Gourves Pierre-Yves, Godfrin Yoann, Buchet Vincent, Stachowski-Haberkorn Sabine. Trophic transfer of copper decreases the condition index in Crassostrea gigas spat in concomitance with a change in the microalgal fatty acid profile and enhanced oyster energy demand. Science of the Total Environment, in press.
Chouvelon Tiphaine, Auby Isabelle, Mornet Line, Bruzac Sandrine, Charlier Karine, Ferreira Araújo Daniel, Gonzalez Jean-louis, Gonzalez Patrice, Gourves Pierre-Yves, Méteigner Claire, Perrière-Rumèbe Myriam, Rigouin Loïc, Rozuel Emmanuelle, Savoye Nicolas, Sireau Teddy, Farida Akcha. Role of suspended particulate material on the growth and metal bioaccumulation in oysters from a French coastal semi-enclosed production area, the Arcachon bay. Journal of Marine Systems, submitted.
Ferreira Araujo Daniel, Knoery Joel, Briant Nicolas, Ponzevera Emmanuel, Chouvelon Tiphaine, Auby Isabelle, Yepez Santiago, Bruzac Sandrine, Sireau Teddy, Pellouin-Grouhel Anne, Akcha Farida (2021). Metal stable isotopes in transplanted oysters as a new tool for monitoring anthropogenic metal bioaccumulation in marine environments: The case for copper. Environmental Pollution, 290, 118012 (10p.) https://doi.org/10.1016/j.envpol.2021.118012