Interaction of Naturally Occurring Phytoplankton with the Biogeochemical Cycling of Mercury in Aquatic Environments and Its Effects on Global Hg Pollution and Public Health

The biogeochemical cycling of mercury in aquatic environments is a complex process driven by various factors, such as ambient temperature, seasonal variations, methylating bacteria activity, dissolved oxygen levels, and Hg interaction with dissolved organic matter (DOM). As a consequence, part of the Hg contamination from anthropogenic activity that was buried in sediments is reinserted into water columns mainly in highly toxic organic Hg forms (methylmercury, dimethylmercury, etc.). This is especially prominent in the coastal shallow waters of industrial regions worldwide. The main entrance point of these highly toxic Hg forms in the aquatic food web is the naturally occurring phytoplankton. Hg availability, intake, effect on population size, cell toxicity, eventual biotransformation, and intracellular stability in phytoplankton are of the greatest importance for human health, having in mind that such Hg incorporated inside the phytoplankton cells due to biomagnification effects eventually ends up in aquatic wildlife, fish, seafood, and in the human diet. This review summarizes recent findings on the topic of organic Hg form interaction with natural phytoplankton and offers new insight into the matter with possible directions of future research for the prevention of Hg biomagnification in the scope of climate change and global pollution increase scenarios.

Automated summary

The biogeochemical cycling of mercury in aquatic environments is influenced by factors such as temperature, seasonal variations, bacterial activity, dissolved oxygen levels, and interactions with dissolved organic matter. This process leads to the reinsertion of mercury contamination from human activities into aquatic systems, particularly in toxic forms like methylmercury. Phytoplankton play a crucial role in the transfer of methylmercury to the aquatic food web, posing risks to human health through consumption of seafood. This review summarizes recent findings on the interaction between organic mercury forms and natural phytoplankton and highlights the need for further research to prevent mercury biomagnification under climate change and increasing pollution scenarios.