Collaborative research: Non-Local Bacterial Transport of Nitrate within Sediments Underlying Oxygen Deficient Zones: A New Twist in the N Cycle

在这个项目中，南加州大学和普林斯顿大学的研究人员将调查非本地细菌硝酸盐运输与南加州海岸和东亚热带北太平洋地区缺氧盆地的区域氮损失之间的联系。最近的研究表明，在圣巴巴拉盆地，底栖硝酸盐的消耗非常迅速（Sigman等人，2003;哈蒙德等人，2006年）。然而，在这个盆地中的N，S和C通量的预算可能只得到满足，如果大部分（高达100%的潜在）的硝酸盐吸收在SBB沉积物不涉及呼吸的有机碳，而是耦合到硫化物的氧化。在该区域发现的细菌Thioploca和Beggiatoa已知在细胞内积累高达500 mM的硝酸盐。它们将硝酸盐输送到沉积物中，最深可达数十厘米，在那里硝酸盐用于硫化氢氧化。这种非本地硝酸盐运输（分层沉积物内）清楚吗？休息？成岩序列的规律 在SBB和圣莫尼卡和圣佩德罗盆地的初步工作产生的地球化学和同位素证据是一致的细菌运输和随后的硝酸盐转化为二氮（N2）在沉积物中的深度。该项目的研究人员假设，硝酸盐的非本地细菌运输可能是一个重要的，但以前被忽视的汇在区域和全球的氮预算的缺氧区。 他们将（1）研究有利于硝酸盐非本地细菌运输的地球化学框架;（2）确定这一过程对固定氮净区域损失的相对贡献;（3）确定和量化这一现象对上覆水柱中硝酸盐的Δ 15 N的影响;以及（4）调查微生物硝酸盐运输与其他还原硝酸盐的反应（如厌氧氨氧化）的可能耦合。该项目包括一次长时间航行和四次短暂航行到圣佩德罗盆地，将为南加州大学和普林斯顿大学的本科生和研究生参与海洋学研究提供一个框架。 在附近的卡塔利纳岛上正在进行的国际地球生物学夏季课程中，硝酸盐运输细菌的迹象一直是并将继续是一个感兴趣的话题。最后，该项目将支持一名年轻女研究员的科学发展，她是这项建议的带头人。

In this project, researchers at the University of Southern California and Princeton University will investigate the link between non-local bacterial nitrate transport and regional nitrogen losses in oxygen deficient basins off the Southern California coast and regions of the Eastern Subtropical North Pacific. Recent studies suggest remarkably rapid benthic nitrate consumption in the Santa Barbara Basin (Sigman et al., 2003; Hammond et al., 2006). Yet, budgets for N, S and C fluxes in this basin may be only satisfied if a large fraction (up 100 % potentially) of nitrate uptake in SBB sediments does not involve the respiration of organic carbon, but instead is coupled to oxidation of sulfides. The bacteria Thioploca and Beggiatoa, found in this region, are known to accumulate up to 500 mM of nitrate intracellularly. They transport nitrate into the sediments, up to depths of tens of centimeters where nitrate is used for hydrogen sulfide oxidation. This non-local nitrate transport (within laminated sediments) clearly ?breaks? the rules of diagenetic sequence. Preliminary work in SBB and Santa Monica and San Pedro Basins produced geochemical and isotopic evidence which is consistent with bacterial transport and subsequent transformation of nitrate to dinitrogen (N2) at depth in the sediments.The researchers on this project hypothesize that non-local bacterial transport of nitrate may be a significant but previously overlooked sink in the regional and global N budgets of oxygen deficient zones. They will (1) examine the geochemical framework favorable for non-local bacterial transport of nitrate; (2) determine the relative contribution of this process to net regional losses of fixed N; (3) identify and quantify the effects of this phenomenon on the ä15N of nitrate in the overlying water column; and (4) investigate the possible coupling of microbial nitrate transport to other reactions that reduce nitrate, such as Anammox.This project, which includes one long cruise and four brief cruises to San Pedro Basin, will provide a framework for potential involvement of USC and Princeton undergraduate and graduate students in oceanographic research. The tell-tale signs of nitrate-transporting bacteria have been and will continue to be a topic of interest in the ongoing International Geobiology summer course on nearby Catalina Island. Finally, this project will support the scientific development of a young female researcher who spear-head this proposal.