Collaborative Research: Mercury Biogeochemistry on the Continental Shelf and Slope

对海洋环境中一甲基汞的来源和循环知之甚少。大陆架和斜坡沉积物似乎是MMHg的潜在来源。因此，康涅狄格大学和赖特州立大学的研究人员计划进一步了解影响西北大西洋大陆架和斜坡沉积物中MMHg产生和动员的生物地球化学过程和反应。为了实现他们的目标，科学家们建议在该地区进行三次实地和实验室实验，一次是在夏末沉积汞（Hg）甲基化最佳且水柱分层的时候，两次是在冬末/早春水柱混合良好且MMHg产量减少的时候。结果将用于验证以下假设：(1)沉积物中MMHg的产生取决于Hg（II）底物的有效性，这是Hg负荷、有机物、硫化学和甲基化细菌活性的函数；(2)水体中MMHg的垂直和水平分布在夏季指示了原位沉积生产，而在冬季则出现了有限的垂直和水平分离；(3)硫酸盐还原菌是陆架/斜坡沉积物中产生MMHg的微生物的主要功能群；(4)水柱甲基化不是陆架水域MMHg的主要来源；(5) MMHg在陆架浮游食物网中生物积累和生物放大。关于更广泛的影响，关于大陆架/斜坡沉积物在甲基汞生产中的作用的知识填补了我们目前对汞的生物地球化学理解中的一个重要空白。作为该项目的一部分，康涅狄格大学的一名研究生和一名本科生以及赖特州立大学的一名研究生和一名本科生将得到支持和培训。

Little is known about the sources and cycling of monomethylmercury (MMHg) in the marine environment. Continental shelf and slope sediments appear to be a potential source of MMHg. For this reason, investigators from the University of Connecticut and Wright State University, plan to further our understanding of the biogeochemical processes and reactions affecting MMHg production and mobilization from sediments on the continental shelf and slope of the northwestern Atlantic Ocean. To attain their goal, the scientists propose to carry out field and laboratory experiments during three cruises to this region, one in late summer when sedimentary mercury (Hg) methylation is optimal and the water column is stratified and two cruises in late winter/early spring when the water column in well mixed and MMHg production is reduced. Results would be used to test the following hypotheses: (1) MMHg production in sediments is dependent on the availability of Hg(II) substrate, which is a function of Hg loadings, organic matter, sulfur chemistry, and activity of methylating bacteria; (2) vertical and horizontal distributions of MMHg in the water column would be indicative of in situ sedimentary production in the summer, whereas limited vertical and horizontal segregation would occur in the winter; (3) sulfate reducing bacteria are the principal functional group of microorganisms producing MMHg in sediments on the continental shelf/slope; (4) water column methylation is not a major source of MMHg in continental shelf waters; and (5) MMHg bioaccumulates and biomagnifies in planktonic food webs on the shelf. As regards broader impacts, knowledge on the role of continental shelf/slope sediments in the production of methyl mercury fills an important gap in our current understanding of the biogeochemistry of mercury. One graduate and one undergraduate student from the University of Connecticut and one graduate and one undergraduate student from Wright State University would be supported and trained as part of this project.