Trophodynamics and distribution of silver in a Patagonia mountain lake.

Silver (Ag) ions are among the most toxic metallic ions to aquatic biota. In southern Argentina, fish from Patagonian lakes have liver Ag concentrations [Ag] among the highest ever reported globally. Silver concentration in phytoplankton from Lake Moreno (1.82±3.00μgg(-1) dry weight, DW) was found to be significantly higher than [Ag] in zooplankton (0.25±0.13μgg(-1)). Values in snails and decapods (0.60±0.28μgg(-1) and 0.47±0.03μgg(-1) respectively), were higher than in insect larvae (0.28±0.39μgg(-1) for Trichoptera). We examined trophic transfer of Ag in the biota using stable nitrogen and carbon isotopes ratios (δ(15)N and δ(13)C respectively). Silver concentrations in the biota of Lake Moreno were not associated with any particular C source, as assessed by δ(13)C. Hepatic [Ag] significantly increased with trophic position, as measured by δ(15)N, within the brook trout sample set. Biodilution of Ag was observed between primary producers and small forage fish when whole body [Ag] was analyzed. Nevertheless, when considering whole food web biomagnification and hepatic [Ag] of top predator fish, a significant positive regression was found between [Ag] and trophic position, as measured by δ(15)N. The importance of species-specific and tissue-specific considerations to obtain more information on Ag trophodynamics than that usually presented in the literature is shown. To the best of our knowledge, this is the first study in assessing Ag trophodynamics and tissue-specific biomagnification in a whole freshwater food web.