Fate and transfer of toxic compounds through the aquatic food web. Looking for markers of aquatic pollution in human food and drinking water.

GRIBOFF, JULIETA; MONFERRAN, MAGDALENA V.; WUNDERLIN, DANIEL A.; HORACEK, MICHA

Congreso; SETAC Latin America 12th Biennial Meeting; 2017

Aquatic ecosystems are directly or indirectly affected by pollutants, which may have deleterious effects for the aquatic biota. Heavy metals are among main pollutants, which are easily transported and accumulated in the aquatic web, being one important pathway by which humans can be exposed to environmental toxics.The use of stable isotope nitrogen (δ15N) constitutes a valuable tool to evaluate biomagnification of contaminants in a food chain. The trophic transfer of elements can be estimated using relationships between the element concentration and δ15N of studied species. On the other hand, δ 15N has also been used to trace the impact of anthropic activities, mainly untreated sewage discharges, among others, on the environment allowing distinguishing regions with different types of contamination, as well as areas of greater or lesser risk for food production.Our current research is focused on the evaluation of the trophic transfer behavior of metals and metalloids within a limited aquatic food web (plankton, shrimp (Palaemonetes argentinus) and fish (Odontesthes bonariensis), along three reservoirs from the Province of Córdoba (Argentina), with different eutrophication conditions: San Roque (SR), Los Molinos (LM) and Río Tercero (RT). Additionally, we look to verify the feasibility of using δ15N as chemical marker of anthropic pollution in different compartments of these reservoirs, namely water and different levels of the food web (plankton, shrimps and fish). Multi-elemental analysis was performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Stable isotope ratios (δ15N) was measured by IRMS. The range of δ15N values in studied species suggested a food chain with increasing trophic levels as follows: plankton-shrimp-fish, which is consistent with what is already known about the dietary habits of fish (Silverside). Positive slopes were found for P, Ga, Cu, Zn, As, Sr, Ba and Hg in SR reservoir; but only Ag, Hg and P showed positive slope in LM reservoir, while P and Hg had positive slope in RT reservoir. Only the regression for Hg and P in LM, Hg in RT and P in SR showed a significant positive slope (P < 0.0001), demonstrating the biomagnification of these elements through the trophic chains studied. Conversely, significant negative slopes (P < 0.0001) were found for the rest of the elements in three reservoir studied, indicating biodilution of these elements. Results also show distinctive patterns in δ15N between studied reservoirs, allowing the identification of a reservoir (SR) highly influenced by sewage, which was evident in water and biota living in this reservoir. Further research studies are being conducted to confirm this result, looking for 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 reservoirs.