All what you wanted to know about mercury in the Mediterranean Sea…

Summarising the critical review on the mercury budget, fate and health consequences in the Mediterranean Sea proposed by Cossa and his co-workers (2022, see reference below) is a challenge owing to its exhaustivity. This assessment updates current knowledge on the sources, biogeochemical cycling, and mass balance of mercury (Hg) in the Mediterranean Sea. Among others, the reader learns that the Mediterranean waters have a high methylation capacity, thus being a source of methylmercury (MeHg) for the North Atlantic Ocean; that MeHg represents up to 86% of the total Hg; that it is enriched in low oxygenated waters and twice higher in the western than in the eastern basin; that this concentration difference is transferred through the food webs and the Hg content in predators, many of them still exceed European Union regulatory Hg thresholds; that human exposure is quite variable between the different countries.

The insufficiencies of knowledge of Hg cycling in the Mediterranean Sea are also underlined, with the strong recommendation that assessment of global change impacts under the Minamata Convention Hg policy requires long-term observations and dedicated high-resolution Earth System Models for the Mediterranean region.

Figure: Mercury annual mass fluxes in the Mediterranean Sea (Mg y^-1). In the dark yellow rectangles are the Hg inventories (Mg) in sub-basins.

Reference:

Cossa, D., Knoery, J., Bănaru, D., Harmelin-Vivien, M., Sonke, J. E., Hedgecock, I. M., Bravo, A. G., Rosati, G., Canu, D., Horvat, M., Sprovieri, F., Pirrone, N., & Heimbürger-Boavida, L.-E. (2022). Mediterranean Mercury Assessment 2022: An Updated Budget, Health Consequences, and Research Perspectives. Environmental Science & Technology. Access the paper:10.1021/acs.est.1c03044