Differentiation and characterization of three lakes in Córdoba (Argentina) using carbon and nitrogen stable isotopes.

GRIBOFF, JULIETA; HORACEK M; WUNDERLIN, D.A.; MONFERRÁN, M. V.

Buenos Aires

Congreso; 11° Meeting SETAC-LatinAmerica; 2015

SETAC-LATINOAMÉRICA

Stable isotopes have become useful for tracing food webs and stimulating nutrient and energy flow in aquatic ecosystems. Therefore, this analysis is a promising tool for monitoring changes in the contribution of human N sources as an effective and direct indicator of human N pollution, providing further information for the identification of sewage pollution. Based on stable isotope analysis as chemical markers, this study aims at finding methods that could be reliably used to understand the impact of potential pollutants on aquatic ecosystems. For this reason, we measured δ13C and δ15N values in different abiotic matrices, like water and sediment, and in diverse organisms, from primary producers to upper consumers. Considering our goal, the three most important lakes in Córdoba were sampled: San Roque (SR), Los Molinos (LM) and Río Tercero (RT). Several activities conducted in the surroundings of these lakes can be sources of different types of pollution. The SR Lake supplies drinking water to Córdoba city, and is also intended for recreational use. It is surrounded by cities and settlements which are not fully connected to the public sewage system. The LM Lake provides water to the southeastern area of the city of Córdoba and is used for recreational activities and irrigation. The RT Lake is the largest artificial reservoir in the province of Córdoba, and it is used for water supply and industrial activities, as well as for providing cooling water for a nuclear power plant. Samples of water, sediment, plankton, shrimp (Palaemonetes argentinus) and fish (Odontesthes bonariensis) were collected from each lake. Stable isotope analyses were performed in an Isotope Ratio Mass Spectrometer (IRMS), connected to an elemental analyser (both Thermo Fisher Scientific). The results indicated notorious differences in δ13C and δ15N between samples in the studied lakes, showing the ability to identify lakes exposed to anthropogenic sewage. All samples from the SR Lake presented the highest δ15N values, indicating that this lake has the greatest influence of sewage on the lake ecology. It is worth mentioning that the information provided by our analysis is not exhaustive, and further research studies are necessary to confirm this preliminary result, whether it is possible to link sewage discharges with levels of stable isotopes in biota, including edible fish, allowing to point out the risk for people drinking water or eating fish from such impacted lakes.