Collaborative Research: Mercury Biogeochemistry on the Continental Shelf and Slope

人们对海洋环境中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毫米汞柱的潜在来源。为此，康涅狄格大学和莱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毫米汞生产和动员的生物地球化学过程和反应。为了实现他们的目标，科学家们提议在前往该地区的三次航行中进行实地和实验室实验，一次是在夏末，此时沉积汞(Hg)甲基化最佳，水柱分层；两次航行是在冬末/初春，此时混合良好的水柱和毫米汞产量减少。结果将被用来检验以下假设：(1)沉积物中的毫米汞生产依赖于汞(II)底物的可用性，这是汞负荷、有机质、硫化学和甲基化细菌活性的函数；(2)水柱中毫米汞的垂直和水平分布指示夏季就地沉积生产，而在冬季发生有限的垂直和水平分离；(3)硫酸盐还原细菌是大陆架/斜坡沉积物中产生毫米汞的主要微生物功能群；(4)水柱甲基化不是大陆架水域中毫米汞的主要来源；(5)MmHg在陆架浮游食物网中积累和放大。至于更广泛的影响，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毕业生和一名本科生以及莱特州立大学的一名毕业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.