Assessment of Water Genotoxicity in Four Coastal Lagoons in Southern Brazil Using Fish Bioassays.

The water in the coastal lagoons of the Tramandaí River Basin (TRB) in southern Brazil is affected by domestic, industrial, and agricultural effluents. The towns within the TRB experience significant population surges during peak vacation periods, which may further impact water quality. The micronucleus (MN) test is a useful tool for detecting genotoxic effects induced by pollutant mixtures and can serve as an indicator of water quality. This study aimed to evaluate the temporal variation in genotoxic potential and fecal contamination of water samples from four coastal lagoons within the TRB. Water sampling was conducted across four periods in the Cidreira, Fortaleza, Gentil, and Tramandaí lagoons. Specimens of Astyanax jacuhiensis were exposed to water samples and a negative control for 96 h in laboratory conditions. The frequencies of MN and other nuclear abnormalities (NA) were analyzed in the erythrocytes of the fish. Thermotolerant coliforms were assessed as an indicator of fecal contamination. Significant differences were noted during the summer season, with higher MN frequencies observed in the Gentil lagoon and increased NA frequencies in both the Gentil and Cidreira lagoons compared to the control group. During warmer periods, thermotolerant coliform counts exceeded the limits established by Brazilian legislation for recreational use in the Tramandaí, Gentil, and Cidreira lagoons. These results indicate temporal variations in fecal contamination and water genotoxicity in the TRB lagoons, with the highest values recorded in summer likely linked to increased tourism in the region.