210Po and 210Pb trophic transfer within the phytoplankton-zooplankton -anchovy/sardine food web: a case study from the Gulf of Lion (NW Mediterranean Sea)

The transfer of Po-210 and Pb-210 in the food web of small pelagic fishes (from phytoplankton and zooplankton to anchovy Engraulis encrasicolus and sardine Sardina pilchardus) is investigated in the Gulf of Lion (GoL). We present original data of Po-210 and Pb-210 activity concentrations, C and N stable isotope ratios, measured (i) from different size classes of phytoplankton and zooplankton during spring and winter in different environments of the GoL, and (ii) in two fish species. Significant spatial patterns based on Po-210, Pb-210 activity concentrations and Po-210/Pb-210 ratios in the different plankton size classes are evidenced by hierarchical clustering, both in spring and winter. This variability, also observed for C and N stable isotopes ratios, is connected to local specific pelagic habitats and hydrodynamics. The sampling strategy suggests that Po-210 bioaccumulation in the GoL remains at a constant level from the first (dominated by phytoplankton) to the second trophic level (zooplankton), while Pb-210 bioaccumulation shows an increase in winter. Based on stable N isotope ratios and Po-210 activity concentrations measured in anchovies and sardines, we evidence Po-210 bio-magnification along the trophic food web of these two planktivorous pelagic fishes. (C) 2015 Elsevier Ltd. All rights reserved.