Search

Mercury (Hg) biomagnification in fish food chains is a relevant subject due to the high fish consumption of the Amazonian population and the high toxicity of this metal. In the Amazon, floodplain lake hydrodynamics change considerably along the four seasons of the hydrological cycle (rising water, high water, falling water and low water), which can influence Hg bioaccumulation in fish. The main aim of this study was to evaluate if Hg biomagnification is influenced by seasonality in a floodplain lake (Puruzinho Lake) in the Brazilian Amazon. Additionally, the influence of food chain modeling on measurement of Hg biomagnification was tested. Hg concentrations and stable isotope signatures (carbon and nitrogen) were estimated in four species, Mylossoma duriventre (herbivorous), Prochilodus nigricans (detritivorous), Cichla pleiozona (piscivorous) and Serrasalmus rhombeus (piscivorous). The “trophic magnification slope” (TMS) of the food chain composed by the four species was calculated and compared among the four seasons. There was no significant seasonal variation in TMS among rising water, high water, falling water and low water seasons (p = 0.08), suggesting that Hg biomagnification does not change seasonally. However, there was significant variation in TMS among different food chain models. Lower TMS was observed in a food chain composed of detritivorous and piscivorous fish (0.20) in comparison with a food chain composed of the four species (0.26). The results indicate food chain modeling influences TMS results.

This work evaluated the spatial and temporal variations for metal concentrations (Fe, Mn, Cu, Zn, Ni, Cr e Pb) in water hyacinths [Eichhornia crassipes (Mart.) Solms)] (root and leaves), the particulate material adhering to their roots and the sediment along the Paraíba do Sul River (PSR – high, medium and low) and Imbé River, both in southeastern Brazil. Samples were collected in 2006 at the rainy and dry seasons. Iron andMn showed the highest concentrations in all samples for both rivers. Roots presented the highest concentrations for all metals. Metal concentrations in the water hyacinths suggest that in the dry season, particularly in the low and medium PSR, metals were more easily bioassimilated, probably due to geochemical and anthropogenic particularities of each region. Overall, PSR presented high contents of metals Cu, Zn, Ni, Cr and Pb compared to the Imbé River, but lower concentrations than those admittedly polluted rivers around the world.