Mercury isotopes identify near-surface marine mercury in deep-sea trench biota
Blum, J.D.; Drazen, J.C.; Johnson, M.W.; Popp, B.N.; Motta, L.C.; Jamieson, A.J. (2020). Mercury isotopes identify near-surface marine mercury in deep-sea trench biota. Proc. Natl. Acad. Sci. U.S.A. 117(47): 29292-29298. https://dx.doi.org/10.1073/pnas.2012773117
In: Proceedings of the National Academy of Sciences of the United States of America. The Academy: Washington, D.C.. ISSN 0027-8424; e-ISSN 1091-6490, more
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| Keywords |
Aquatic sciences > Marine sciences > Earth sciences > Oceanography
Deep sea
Mercury (metal)
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| Author keywords |
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| Authors | | Top |
- Blum, J.D.
- Drazen, J.C.
- Johnson, M.W.
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- Popp, B.N.
- Motta, L.C.
- Jamieson, A.J.
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| Abstract |
Mercury isotopic compositions of amphipods and snailfish from deep-sea trenches reveal information on the sources and transformations of mercury in the deep oceans. Evidence for methyl-mercury subjected to photochemical degradation in the photic zone is provided by odd-mass independent isotope values (Δ199Hg) in amphipods from the Kermadec Trench, which average 1.57‰ (±0.14, n = 12, SD), and amphipods from the Mariana Trench, which average 1.49‰ (±0.28, n = 13). These values are close to the average value of 1.48‰ (±0.34, n = 10) for methyl-mercury in fish that feed at ∼500-m depth in the central Pacific Ocean. Evidence for variable contributions of mercury from rainfall is provided by even-mass independent isotope values (Δ200Hg) in amphipods that average 0.03‰ (±0.02, n = 12) for the Kermadec and 0.07‰ (±0.01, n = 13) for the Mariana Trench compared to the rainfall average of 0.13 (±0.05, n = 8) in the central Pacific. Mass-dependent isotope values (δ202Hg) are elevated in amphipods from the Kermadec Trench (0.91 ±0.22‰, n = 12) compared to the Mariana Trench (0.26 ±0.23‰, n = 13), suggesting a higher level of microbial demethylation of the methyl-mercury pool before incorporation into the base of the foodweb. Our study suggests that mercury in the marine foodweb at ∼500 m, which is predominantly anthropogenic, is transported to deep-sea trenches primarily in carrion, and then incorporated into hadal (6,000-11,000-m) food webs. Anthropogenic Hg added to the surface ocean is, therefore, expected to be rapidly transported to the deepest reaches of the oceans. |
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