Metal Levels in Water and the Muscle Tissue of Fishes in the Cachorros River, São Luís Island, State of Maranhão, Brazil

Abstract

The present study evaluates physicochemical variables, perform a microbiological analysis as well as determine heavy metal concentrations in the water and muscle tissue of fishes from the Cachorros River. The analysis of metal concentrations in the estuarine water revealed high levels of Fe and Al, with values above the limits established by Brazilian legislation. The concentration of total coliforms and thermotolerant coliforms tended to be higher in the rainy season. Regarding metal concentrations in the muscle tissue of fishes, high levels of Pb and Cd were found, especially in carnivorous and detritivorous species, with values above the limits established by national legislation. Two-factor analysis of variance revealed that only Pb demonstrated a significant interaction between seasonality and the feeding habits of the fish fauna, with higher concentrations of this metal in the dry season among detritivorous species in comparison to herbivorous species. The present findings demonstrate the contamination pattern that has been occurring in the Cachorros River, as evidenced by the concentration of trace metals in both the water and muscle tissue of fishes, which are an important source of protein as well as an economic resource for the population of this river basin.