δ15N as an indicator of freshwater systems suitable for edible fish production

Abstract

Anthropogenic inputs are affecting freshwaters. Stable isotope ratios of nitrogen (δ15N) are useful to track anthropogenic pollution in food webs across different habitats, species and trophic levels. Córdoba province (Argentina) has serious problems of eutrophication and pollution in some of its freshwater reservoirs. To evaluate the different anthropogenic inputs in the three most important reservoirs in Córdoba: San Roque Lake (SRL), Los Molinos Lake (LML) and Río Tercero Reservoir (RTR), δ15N was measured in water, plankton, shrimp (Palaemonetes argentinus) and fish (Odontesthes bonariensis) muscle samples. Results show that δ15N values of SRL samples (δ15N values between 14.9 and 20.0?) are higher than those of the analogous samples from the other reservoirs, and denote a high influence of sewage discharge in this lake. The results show that the sewage isotopic signals in water were transferred to primary producers, then to mobile consumers, including fish. The findings of this study suggest that this reservoir is a source apparently not safe for food production, like edible fish. Finally, biota has proven to be a sensitive organism whose δ15N value can be used as bioindicator for pollution and human impact on the ecosystem in which it lives.