76 - Using Mercury Isotopes to Trace Methylmercury Sources of Deep-sea Fauna Living in Extreme Ecosystems

Oceans are the primary mercury (Hg) reservoir on the surface Earth where the toxic methylmercury (MeHg) is produced. However, Hg and MeHg sources and cycling in deep oceans are not well understoood. We measured concentrations of total Hg (THg) and MeHg, as well as THg stable isotopes in fauna (amphipod, mussel, snail, etc.) from different deep-sea extreme ecosystems (trench, hydrothermal vent and cold seep). We find that the hydrothermal fauna had significantly higher THg concentrations of 927 ± 1883 ng/g than fauna at the trench (547 ± 236 ng/g) and cold seeps (109 ± 90 ng/g). In contrast, MeHg concentrations in fauna from hydrothermal vents (61 ± 172 ng/g, 3% of THg concentrations) and cold seeps (4.62 ± 0.28 ng/g, 7% of THg concentrations), were much lower than trench fauna (152 ± 222 ng/g, 28% of THg concentrations). Both δ202Hg (-0.05 to 0.54‰) and Δ199Hg (1.26 to 1.70‰) of trench fauna are comparable to marine fishes at 300-600 m depth, indicating that the accumulated MeHg in trench fauna originates from the upper ocean (

Authors: Jingjing Yuan, Ruoyu Sun, Yi Liu, Shun Chen, Xiaotong Peng, Lars-Eric Heimbuerger-Boavida