Frontiers in Marine Science (Nov 2015)
Mercury and selenium relationship in a tropical estuarine fish
Abstract
Aquatic systems have been considered as final sinks for persistent and bioaccumulative toxicants (PBTs), such as metals and organohalogen compounds. Among the trace elements, non-essential metals deserve special attention due to their toxicity. In this context, mercury (Hg) should be highlighted due to its toxic effects, which comprise neurotoxicity, nephrotoxicity, hepatotoxicity, genotoxicity, among others. Several studies have highlighted the selenium-mediated methylmercury detoxification process, via mercury selenide formation in tissues of marine vertebrates. Despite being an essential element, selenium may also be toxic in high concentrations. This study focused on Guanabara Bay (GB), a heavily polluted urban estuary in Rio de Janeiro state (Brazil), where the whitemouth croaker (Micropogonias furnieri) provides a valuable fishery resource. Therefore, hepatic (Hg and Se) and muscular (Hg) concentrations of these elements were determined in GB whitemouth croakers. Mercury and selenium measurements were performed by cold vapor atomic absorption spectrometry (CV-AAS) and electrothermal AAS (ET-AAS), respectively. Total mercury (THg) concentrations in muscle (n=19) ranged from 184.9 to 858.6 (ng/g), while in liver they varied from 11.05 to 1188 (ng/g). Hepatic selenium concentrations ranged from 7820 to 40085 (ng/g). The hepatic Se:THg molar ratio ranged from 40,8 to 3102,5. The results showed a significant correlation between hepatic mercury and selenium levels, but the molar ratio suggests the absence of mercury selenide formation. Some of the Se concentrations found were above the threshold level for freshwater fish (12000 ng/g); however, it is not yet clear if these concentrations are toxic for marine fish as well. More studies are necessary for evaluating the impact of such exposure in fish from Guanabara Bay.
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