Preliminary Toxicological Evaluation in the Conlara Basin (San Luis, Argentina) Through the Use of Different Bioindicator Species

J.M. PÉREZ IGLESIAS; C.A. ALMEIDA; P.L. COLOMBETTI; PATRICIA S. GONZÁLEZ; J. DARUICH

Mar del Plata

Congreso; SETAC Latin America 14th Biennial Meeting; 2022

SETAC

Anthropic activities can be a source of pollution and have a great negative impact on biodiversity. The Conlara River basin is located northeast of San Luis (Argentina), being an area of tourist activity and mixed agricultural exploitation (livestock and intensive agriculture). The objective of this work was to evaluate the current state of the basin by combining bioindicator species and ecotoxicological tools. Five sampling sites were selected along the basin from S1 (upstream) to S5 (downstream). Water and sediment samples were taken from each site to carry out the bioassays on the following bioindicators: Oocistys sp., Hyalella sp. and Rhinella arenarum. In the samples, heavy metals and physicochemical parameters were determined. The bioassays were carried out to evaluate mortality and under controlled laboratory conditions at different exposure times according to the species: Oocistys sp. (48h), Hyalella sp. (96h) and R. arenarum (168h). For data analysis, multivariate statistical techniques (PCA) and Probit analysis were used to obtain toxicological parameters such as lethal time 50 (TL50) and growth inhibition (IC50). The values of the physicochemical parameters showed an increase in conductivity, organic matter, phosphorus and heavy metals as the water course progresses (S1 to S5). In the case of Oocystis sp., a significant decrease was observed from S2 that allowed estimating IC50 values: S2 = 126.05h, S3 = 64.24h, S4 = 43.87h and S5 = 28.96h. Mortality analyzes revealed only TL50 = 10.88h values in S4 for Hyalella sp. while in S5 the mortality was 100% in Hyalella sp. and R. arenarum. The first 2 components of the PCA explained 84.05% of the total variability. This analysis showed that S4 and S5, in contrast to S1, S2 and S3, were characterized by high concentrations of heavy metals and organic matter, related to an inhibition in algae and high mortality in invertebrates and aquatic vertebrates. In addition to this, analyzing macroinvertebrates as ecological indicators, more sensitive families (Ephemeroptera) identified in S1 and more tolerant organisms Chironomidae) found mainly in S4 and S5 were observed. This preliminary toxicological analysis tested on different aquatic bioindicators shows a deterioration downstream of the basin (S4 and S5) that could be explained by the anthropic practices of the region.