Interactions between mercury and phytoplankton: Speciation, bioavailability and internal handling
In the present review, key interactions between Hg and phytoplankton are described and discussed in order to highlight the role of phytoplankton in the biogeochemical cycle of Hg and to understand direct or indirect Hg effects on them. Phytoplankton are exposed to various Hg species in surface waters. By Hg uptake, phytoplankton affect the concentration, speciation and fate of mercury in aquatic systems. The mechanisms by which phytoplankton take up Hg are still not well known, but several studies have suggested that both facilitated transport and passive diffusion could be involved. Once internalized, Hg will impact several physiological processes, including photosynthesis. To counteract these negative effects, phytoplankton have developed several detoxification strategies, such as the reduction of Hg to elemental Hg0 or its sequestration by intracellular ligands. Based on the toxicological studies performed so far in the laboratory, Hg is unlikely to be toxic to phytoplankton when they are exposed to environmentally relevant Hg concentrations. However, this statement should be taken with caution as questions remain as to which Hg species control Hg bioavailability and about Hg uptake mechanisms. Finally, phytoplankton are primary producers and accumulated Hg will be transferred to higher consumers. Phytoplankton are a key component in aquatic systems and their interactions with Hg still need to be further studied to fully comprehend the biogeochemical cycle of Hg and the impact of this ubiquitous metal on ecosystems. Environ Toxicol Chem © 2013 SETAC
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