Bioindicators and biomarkers of environmental pollution in the middle-lower basin of the Suquía River (Córdoba, Argentina).

The Suquía River middle-lower basin (Córdoba, Argentina) is subject to a strong anthropogenic impact because it receives pollutants from different sources. Recent studies have shown the importance and the need of approaching the monitoring process of water quality from integral perspectives through the use of chemical as well as biological methods. The main goal of this study was to evaluate the fish species Jenynsia multidentata as a bioindicator of environmental pollution in the middle-lower basin of the Suquía River using biotransformation and antioxidant enzymes as well as gill and liver histopathology as biomarkers. We also studied the fish-assemblage characteristics through the fish species pattern variation and the application of a biotic index based on fish data. Our study also included the analysis of a water-quality index, heavy-metal concentrations in sediment and water, and pesticide concentrations in sediment. The chemical analyses of the middle-lower Suquía River basin showed a water-quality degradation gradient. Fish-assemblage structure changed with increasing water pollution, showing a simpler structure at the most polluted area. According to the biotic index, the variation pattern of fish assemblages reflected the aquatic environmental deterioration. Both molecular and histopathological biomarkers reflected the same trend in relation to water quality. However, enzymes varied with more acute precision between seasons. In addition, each enzyme presented with different sensibility. At tissue level, the histopathological analysis detected chronic contamination at both stations and seasons. The present work, which comprises different levels of biological organization together with chemical analyses, generated particular although complementary information, thus evidencing the same trend of aquatic contamination. Thus, the development of integral investigations gives a comprehensive approach and becomes the most effective tool to construct policies both preventive and palliative. Our study constitutes a good model to be applied in other endorheic basins of South America.