大西洋中部海湾陆架断裂前沿的氮动态对比:硝酸盐双同位素和硝化基因丰度的启示

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Yifan Zhu, Margaret R. Mulholland, Corday R. Selden, Dennis J. McGillicuddy Jr, Josie Mottram, P. Dreux Chappell, Weifeng Gordon Zhang, Julie Granger, Katherine E. Crider, Meredith G. Meyer, Peter W. Bernhardt, Hilde Oliver, Sophie Clayton
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引用次数: 0

摘要

观测和模型研究表明,锋面动力学可以提高浮游植物的生产力。本研究测试了锋面系统是否也会增加硝化微生物的丰度,并在 2019 年 7 月横跨大西洋中腹陆架断裂带的重复采样横断面上进行氮回收。我们测量了氨浓度、硝酸盐双同位素(δ15N、δ18O)以及氨氧化古细菌(AOA)和细菌(AOB)的氨单加氧酶亚基 A(amoA)基因。在陆架下层水域,铵浓度超过 2 μmol L-1,这是由于下沉颗粒再生和随后的硝化作用暂时失衡所致。硝酸盐 δ15N 值与铵浓度之间的反相关关系证实,硝酸盐部分或全部来自陆架上的局部硝化。相比之下,陆架断裂前缘带和斜坡海域表层下水域的铵浓度(0.1-0.2 μmol L-1)要低得多,这是因为铵再生和硝化作用之间存在紧密的耦合关系。硝酸盐 δ15N 和 δ18O 与藻类吸收驱动的 1 : 1 比率的偏差表明,在透光区同时存在硝化作用。陆架断裂前沿是 AOA 和 AOB amoA 基因数量分区的生态边界,AOA 在斜坡水域大量存在,而 AOB 在陆架水域大量存在,这可能与铵的供应有关。在某些斜坡站位,湾流入侵引起的等压升降导致深水营养物质输入,从而引起浮游植物生物量出乎意料地增加,使硝化物丰度翻倍,并可能刺激铵再生和硝化作用。这些发现表明,硝化微生物在从陆架到斜坡的盐度梯度上有不同的分布,突出表明了沿岸海域-西部边界流相互作用对氮生物地球化学的重要影响。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Contrasting nitrogen dynamics across the Mid-Atlantic Bight shelfbreak front: Insights from nitrate dual isotopes and nitrifier gene abundance

Contrasting nitrogen dynamics across the Mid-Atlantic Bight shelfbreak front: Insights from nitrate dual isotopes and nitrifier gene abundance

Observations and model studies suggest that front dynamics can enhance phytoplankton productivity. This study tested whether frontal systems also increase the abundance of nitrifying microbes and nitrogen recycling during repeat sampling transects across the Mid-Atlantic Bight shelfbreak in July 2019. We measured ammonium concentrations, nitrate dual isotopes (δ15N, δ18O), and ammonia monooxygenase subunit A (amoA) genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB). In subsurface shelf waters, ammonium concentrations exceeded 2 μmol L−1, due to a temporary imbalance in regeneration from sinking particles and subsequent nitrification. The inverse correlation between nitrate δ15N values and ammonium concentrations confirmed nitrate was partially or entirely from local nitrification on the shelf. In contrast, the shelfbreak frontal zone and slope sea subsurface waters had much lower ammonium concentrations (0.1–0.2 μmol L−1) due to tight coupling between ammonium regeneration and nitrification. The deviation of nitrate δ15N and δ18O from algal uptake-driven 1 : 1 ratio suggests concurrent nitrification in the euphotic zone. The shelfbreak front acted as an ecological boundary where AOA and AOB amoA gene numbers were partitioned, with AOAs abounding in slope waters and AOBs in shelf waters, likely due to ammonium availability. At certain slope stations, deep-water nutrient inputs via isopycnal lifting induced by Gulf Stream intrusions caused unexpectedly high phytoplankton biomass, which doubled nitrifier abundance and potentially stimulated both ammonium regeneration and nitrification. These findings demonstrate distinct distributions of nitrifying microbes along the salinity gradient from shelf to slope and highlight the significant influence of coastal ocean-western boundary current interactions on nitrogen biogeochemistry.

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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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