Human-derived mercury shown to pollute the world's deepest ocean trenches

https://www.eurekalert.org/pub_releases/2020-06/gc-hms061920.php


News Release 22-Jun-2020
Goldschmidt Conference


Scientists have found that man-made mercury pollution has reached the bottom of the deepest part of the ocean - the Marianas Trench. This has significant implications for how mercury affects the marine environment, and how it may be concentrated in the food chain. The findings, which come from two independent research groups, are presented at the Goldschmidt geochemistry conference.

Mercury is toxic to humans and other animals, and has been implicated in environmental disasters in the past, most famously at Minamata in Japan in the 1950's where it led to birth defects and severe neurological symptoms. It tends to be concentrated in marine organisms, where small amounts are ingested by some species which are in turn eaten by larger species, meaning that harmful levels of mercury can be concentrated in animals that sit higher up in natural food webs through the process of bioaccumulation. As an example, this leads to mercury concentrations in swordfish being x40 that of salmon. Mercury is generally poisonous at high levels and can be especially dangerous to the developing foetus.

Now two groups of scientists are independently reporting that both manmade and natural methylmercury, a toxic form of mercury easily accumulated by animals, has been found in fish and crustaceans in the 11,000m deep Marianas Trench in the Pacific Ocean. This work is being reported at the Goldschmidt Geochemistry conference.

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