Metallothionein in the Pond Perch Diplectrum radiale (Teleostei) as a Biomarker of Pollution in Guanabara Bay Estuary, Brazil

Abstract

Guanabara Bay is a semi-closed tropical bay located in the center of metropolitan Rio de Janeiro. The ecological integrity of this system has a spatial gradient, with better environmental conditions near the mouth than in the inner bay. The objectives of this study were to monitor the exposure of the pond perch Diplectrum radiale (Perciformes; Serranidae) to metal pollution, using metallothionein as a specific biomarker, and to detect spatial differences in metal contamination in this large water body. The effects of biological factors (allometric condition factor, size, weight, and reproductive stage) and spatial variations on MT levels were also investigated among sampling sites. The results revealed intraspecific sources of variation influencing MT expression. Therefore, it was not possible to use MT as a sensitive biomarker to distinguish heavy metal pollution among sites within this bay. The spatial heterogeneity of metal bioavailability and the probable mobility of individual fish contributed to those findings. However, the pond perch can still be considered a good target organism to evaluate the effects of metal contamination through comparison with other estuarine ecosystems on the Brazilian coast.