期刊
MARINE ECOLOGY PROGRESS SERIES
卷 482, 期 -, 页码 57-68出版社
INTER-RESEARCH
DOI: 10.3354/meps10240
关键词
Denitrification; Heterotrophic nitrogen fixation; Marine sediments; nifH expression; Direct sediment N-2 fluxes
资金
- Rhode Island Sea Grant College Program
- National Science Foundation's Chemical Oceanography division [OCE 0926859, OCE 0926875]
- Rhode Island EPSCoR program [NSF-0554548, NSF-1004057]
Marine waters are often nitrogen (N) limited. Denitrification, the microbial conversion of nitrate to dinitrogen (N-2) gas, is responsible for significant N removal from the coastal ocean. In contrast, nitrogen fixation, the microbial transformation of N-2 to ammonium, is typically regarded as an inconsequential N source. The imbalance between these 2 processes is responsible, at least in part, for N limitation in the coastal ocean. Organic matter quality and quantity has been shown to determine rates of these critical N cycling processes. We hypothesized that the timing of organic matter deposition to the benthos might also be important in determining which process dominates. We tested this hypothesis using a coupled biogeochemical-molecular approach. We report directly measured net sediment denitrification rates and corresponding expression of nirS, a gene in the denitrification pathway, with the simultaneous expression of nifH, a gene associated with nitrogen fixation. The timing of organic matter deposition determined the magnitude of the net sediment N-2 fluxes. Highest rates of denitrification occurred soon after deposition, and the lowest rates occurred over 200 d after the last deposition event concomitant with increased nifH expression. Phylogenetic evidence suggests that sulfur and sulfate reducers are responsible for the nitrogen fixation. Globally, warming water temperatures, changes in light, and reduced nutrient loads through management intervention have been linked to decreases and/or altered phenology of water column productivity. Based on a conceptual model developed here, we suggest that in these systems, heterotrophic sediment nitrogen fixation may become an important component of the nitrogen budget.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据