Past and future cadmium contamination in fish habitats of the Gironde estuary : an otolith and modeling approach (Supervised by Françoise DAVERAT (Irstea) in partnership with UMR EPOC, Irstea and IPREM LCABIE (Laboratory of Bioinorganic Analytical and Environmental Chemistry)).
The Gironde estuary is impacted by historical metal pollution due to a major industrial activity in its catchment basin. Among trace elements identified as priority pollutants by the European Community (2000/60/EC), cadmium Cd, leader Pb and Nickel Ni, highly toxic trace metals to aquatic organisms, have shown (notably Cd) extremely high concentration for decades in water, sediment (Lanceleur et al., 2011) and biological organisms (Durrieu et al., 2005; Pierron et al., 2008; Lanceleur et al., 2011; Daverat et al., 2012). While metal analysis of soft tissues requires continuous sampling to assess the ongoing status of an aquatic environment (since trace metals may be lost as the tissues regenerate), otolith may offer a permanent record of metal exposure. Aiming at increasing the resolution of otolith tracers, we’ll investigate the possibility to use otolith chemistry as natural tracer of past and present Cd, Pb and Ni contamination of the Gironde, validating for the first time by experimental design, the relationship of Cd, Pb and Ni concentrations measured in otolith, organism tissues (liver and kidney) and water under controlled conditions. Thereafter, otolith collections of European flounder Platichthys flesus collected in the Gironde at different stations located along the salinity gradient will be analysed with a High-Resolution ICPMS coupled with a femtosecond laser to (1) verify the site specific otolith Cd, Pb and Ni signatures, (2) retreive the spatial utilisation of habitats and (3) retreive the Cd, Pb and Ni contamination level of fish habitats for last decades. In the context of the global change, i.e. salinity and SPM changes due to marinisation and river flow decrease at the scale of the Gironde estuary, the second main objective of the project is to model by simulations the future dispersion of Cd, specifically, in fish estuarine habitats coupling (1) obtained knowledges on habitats occupation by fish from otolith chemistry and (2) maps of risk of bioavailable Cd which will be developped taking into account litterature data on Cd concentrations in the Gironde as well as physico-chemical parameters from biological surveys.