Large amounts of mercury likely derived from human activity have infiltrated food webs in deep-sea trenches, a study finds. Mercury, a pollutant found in the atmosphere and on land, is toxic to the nervous system and accumulates in fish consumed by humans. Relatively little is known about mercury levels, sources, and dynamics in oceans, particularly at deep locations. Joel Blum and colleagues collected six snailfish and 25 crustaceans called amphipods from the ocean floor at depths ranging from 6,000 meters to 10,250 meters in the Mariana Trench and Kermadec Trench, both located in the Pacific Ocean. The authors analyzed mercury concentration and isotopic composition in the samples, and measured Δ199Hg, the magnitude of a specific isotopic signature of mercury. The Δ199Hg values for samples from the trenches ranged between 1.13‰ and 2.31‰, with an average of around 1.54‰. These values are close to the previously reported average value of 1.48‰ for fish that feed in the central Pacific Ocean at a depth of approximately 500 meters, where mercury primarily originates from human emissions. According to the authors, the findings suggest that sinking carrion may transport large amounts of mercury, likely originating from human activity, from near-surface waters to bottom-dwelling animals inhabiting the deepest reaches of the world's oceans.
Article #20-12773: "Mercury isotopes identify near-surface marine mercury in deep-sea trench biota," by Joel D. Blum et al.
MEDIA CONTACT: Joel Blum, University of Michigan, Ann Arbor, MI; tel: 734-615-3242; e-mail: jdblum@umich.edu
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Journal
Proceedings of the National Academy of Sciences