Mercury-selenium interactions in aquatic organisms: A review

Abstract

Throughout the last decade, major research efforts have been directed towards the study of aquatic environment pollution. Nevertheless, the consequences of simultaneous interactions between two or more pollutants in the same aquatic organism are still poorly understood. This paper summarizes published work on mercury-selenium interactions in aquatic organisms. Mercury and selenium are naturally occurring in a 1:1 molar ratio in many aquatic organisms and especially in marine mammals. This particular occurrence is well known in laboratory animals and has been attributed to the Hg-Se antagonism. Nevertheless, there is no clear evidence for a natural joint bioaccumulation of Hg and Se in fish, crustaceans and molluscs except for marlin, which has the ability to tolerate very high concentrations of Hg and Se in its organs and tissues. In laboratory experiments, an antagonistic effect of selenium on the toxicity of mercury has been clearly shown for one marine alga species, but a synergy between Se and Hg has been observed for carp eggs. The rate of bioaccumulation of mercury in fish tissues was decreased in a freshwater ecosystem by the addition of selenite in low concentration. Interaction between selenium and mercury in aquatic organisms is real but the true antagonism between these two elements has not yet been clearly shown. Results are sometimes unrelated and contradictory. Possible avenues for progress in this area are discussed.