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 ± 3.00 μg g⁻¹ dry weight, DW) was found to be significantly higher than Ag] in zooplankton (0.25 ± 0.13 μg g⁻¹). Values in snails and decapods (0.60 ± 0.28 μg g⁻¹ and 0.47 ± 0.03 μg g⁻¹ respectively), were higher than in insect larvae (0.28 ± 0.39 μg g⁻¹ for Trichoptera). We examined trophic transfer of Ag in the biota using stable nitrogen and carbon isotopes ratios (δ¹⁵N and δ¹³C respectively). Silver concentrations in the biota of Lake Moreno were not associated with any particular C source, as assessed by δ¹³C. Hepatic Ag] significantly increased with trophic position, as measured by δ¹⁵N, 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 δ¹⁵N. 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.