Sources and transfer of Cu, Hg and Pb into marine food webs using innovative tracers (metal stable isotopes, trophic markers): results of a pilot study in a French coastal area

Copper (Cu), mercury (Hg) and lead (Pb) are elements and contaminants of historical and emerging concerns in coastal environments. Although Cu is considered essential for living organisms, it is bioactive in a narrow range of optimal concentrations. Hg and Pb have no known biological role and are considered toxic towards organisms. Marine consumers incorporate and bioaccumulate these metals mainly through trophic pathways, which are then important to delineate. Since recently, metal stable isotopes are promising to trace origin and processes of the contamination of marine matrices, including biota. As part of the present study conducted within the SCOTTTI and Pollusols programs, we merged integrated trophic markers (carbon and nitrogen stable isotopes, lipid profiles) and metal stable isotopes to investigate i) the trophic transfer of Cu, Hg and Pb within a model food web of a French human-impacted coastal area (Toulon Harbor, NW Mediterranean); and ii) the potential sources of food web contamination. Whenever possible, samples included sediment, suspended organic matter, size fractions of plankton, filter-feeding bivalves (mussels, oysters) and planktivorous fishes, collected at different seasons. Metal- and species-specific patterns throughout the food web were observed, highlighting the role of biological/physiological processes on the observed metal levels and isotope distributions.