Identification of anthropic impact on the food web using carbon and nitrogen stable isotopes as chemical markers. Case study: Three reservoirs with different eutrophication in Córdoba (Argentina).

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

Barcelona

Congreso; 25° Annual Meeting SETAC-Europe.; 2015

SETAC

Stable isotopes have been used to trace the impact of anthropicactivities, mainly untreated sewage discharges, in three reservoirspresenting different degrees of eutrophication. The main goal of ourresearch was finding chemical-isotopic markers that could be used tolink anthropic pollution with changes in different compartments inreservoirs, namely water, sediment, and different levels of the food web(plankton, shrimps and fish).Thus, we measured ?13C and ?15N valuesin various organisms (from primary producers to upper consumers) tounderstand the influence of the different anthropogenic activities on theenvironment and the possibility to distinguish regions with differenttypes of contamination, as well as areas of greater or lesser risk for foodproduction. Study site samplings were carried out during the wet season(April 2014), after a massive rain event in three lakes in Córdoba,Argentina: San Roque, Los Molinos and Río Tercero lakes.San RoqueLake supplies drinking water to Córdoba city, and is also intended forrecreational use. It is surrounded by cities and settlements which are notfully connected to the public sewage system. Los Molinos Lake provideswater to the Southeastern area of the city of Córdoba and is used forrecreational activities and irrigation. In the surrounding agriculture,mainly corn and sorghum are produced. Río Tercero Lake is the largestartificial reservoir in the province of Córdoba, and it is used for watersupply and industrial activities, as well as for providing cooling waterfor a nuclear power plant. We collected water, sediment, plankton,shrimp (Palaemonetes argentinus) and fish (Odontesthes bonariensis)from each lake. Stable isotope analyses were performed in an IsotopeRatio Mass Spectrometer (IRMS), connected with an elemental analyzer(both Thermo Fisher Scientific). Results showed distinctive patterns in?13C and ?15N between the lakes under study, allowing theidentification of lakes more exposed to anthropogenic sewage. SanRoque Lake showed the highest ?15N values for all the samples,indicating the most prominent influence of sewage on the lake ecology.Further research studies are being conducted to confirm this preliminaryresult, providing an interesting alternative to link sewage dischargeswith levels of stable isotopes in biota, including edible fish; thus,pointing out risk for people drinking water or eating fish from suchimpacted lakes.