Identification of anthropogenic impact using nitrogen isotope as chemical markers. Case study: Three reservoirs with different eutrophication in Córdoba (Argentina).

MAGDALENA MONFERRAN; JULIETA GRIBOFF; DANIEL WUNDERLIN; AMÉ, MARÍA VALERIA

Workshop; Africa Food Safety Workshop; 2018

Stable isotopes have been used effectively in ecological studies to trace the impact of Argentinean lakes different components, like potential pollutants, on ecosystems, as well as to trace food webs. Coastal environments are often exposed to different anthropogenic contaminants that can cause evident differences in coastal ecosystems. For this reason the use of various organisms as an indicator offers an important ecological study (Rozic et al., 2014).In this study, we measure δ15N values in various organisms (from primary producers to upper consumers) to understand the influence of the different anthropogenic activities on the environment and the possibility to distinguish regions with different type of contamination, as well as areas of greater or lesser risk to food production.Study site samplings were carried out during April 2014 and April 2017 in three lakes in Córdoba, Argentina: San Roque, Los Molinos and Río Tercero lakes. San Roque Lake supplies drinking water to Córdoba, and is also intended for recreational uses. It is surrounded by cities and settlements which are not fully connected to public sewage system. Los Molinos Lake provides water to the Southeast of the city of Córdoba and is used for recreational activities and irrigation. In the surrounding agriculture dominantly corn and sorghum is produced. Río Tercero lake is the largest artificial reservoir in the province of Córdoba and used for water supply and industrial activities, as providing cooling water for a nuclear power plant. We collected water, plankton, shrimp (Palaemonetes argentinus) and fish (Odontesthes bonariensis) from each lake. Stable isotope analysis was performed an Isotope Ratio Mass Spectrometer, connected with an elemental analyzer (both Thermo Fisher Scientific). Results showed distinct differences in δ15N between the investigated lakes that also identify lakes exposed to anthropogenic sewage. San Roque lake showed the highest δ15N values, for all the samples, indicating the most prominent influence of sewage on the lake ecology. Moreover, highest δ15N values of edible fish from lakes studied was observed during 2017 monitoring campaign with respect to 2015 one, reinforcing the previously observed results and warning about the deterioration of the reservoirsFurther research studies are being conducted to confirm this preliminary result, providing an interesting alternative to link sewage discharges with levels of stable isotopes in biota, including edible fish; thus, pointing out risk for people drinking water or eating fish from such impacted lakes.