Mercury is one of the least concentrated trace elements in the ocean. Yet low levels of Hg in seawater biomagnify millions of times along the marine food chain, reaching harmful levels in predatory fish and their human consumers. Natural and anthropogenic sources of Hg in the ocean remain poorly controlled. It took 10 years of development to find a method for measuring the stable isotopes of Hg in seawater at subpicomolar levels. The isotopic signatures of Hg in the ocean suggest that gas uptake (Hg0) and ionic deposition (HgII) are of equal importance (1:1), which is contrary to our current understanding (1:3). The deposition of HgII is probably overestimated by 2 to 3 times, and the ocean receives less Hg overall. The results of the study suggest that the implementation of anti-pollution measures under the Minamata Convention will probably lead to a more rapid decrease in oceanic Hg levels than previously thought.
Reference:
Jiskra, M., Heimbürger-Boavida, L., Desgranges, M., Petrova, M., Dufour, A., Ferreira-Araujo, B., Masbou, J., Chmeleff, J., Thyssen, M., Point, D., Sonke, J. E. Mercury stable isotopes constrain atmospheric sources to the ocean. Nature, https://doi.org/10.1038/s41586-021-03859-8