Multi-indicators of environmental pollution in the Olaria system, Cananéia, Sao Paulo (SP), Brazil

The assessment of water quality using multiple abiotic and biological indicators is very important for understanding anthropogenic impacts and the health of the ecosystem. The Olaria is a short river system that flows into the Cananeia estuary. This aquatic system crosses the urban center of the city of Cananeia, where it eventually receives untreated domestic wastewater. This study aims to apply multi-indicators of environmental pollution to understand the influence of the Olaria system on the Cananeia estuary. For this purpose, indicators of water quality and genotoxic and pathological responses in fish were used. Data on salinity, pH, and silicates in surface water indicate a more accentuated continental influence in the inner part of the Olaria river system. Moreover, the data recorded on the inner area of the Olaria system, which presents lower hydrodynamic characteristics and the largest urban population, indicated the presence of dissolved oxygen and nutrients (phosphate [P-PO4-3], nitrite [N-NO2-], and ammonium [N-NH4']) at levels that exceed the established limits for water quality by the Brazilian environmental legislation (Conselho Nacional do Meio Ambiente -CONAMA). The presence of Escherichia coli in all analyzed water samples indicates a local or point source of domestic wastewater contamination near the Olaria system. Fish species such as Centropomus undecimalis (Robalo Flexa) and Sphoeroides testudineus (Baiacu Pintado) showed toxicogenetic damage, indicating clastogenic and/or aneugenic exposure in the aquatic environment. Hepatic pathologies such as pyknosis nuclei, inflammation, hepatocyte swelling, and necrosis were found in all specimens evaluated, and C. undecimallis exhibited all these pathological changes. These results highlight the importance of biomonitoring the effects of anthropogenic disturbance on the aquatic biota that frequent the Olaria system and are dependent on the water quality.