Benthic nitrogen cycling traversing the Peruvian oxygen minimum zone
Benthic nitrogen cycling traversing the Peruvian oxygen minimum zone
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DOI：
10.1016/j.gca.2011.08.010
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发表时间：
2011-10-15
影响因子：
5
通讯作者：
Wallmann, K.
中科院分区：
文献类型：
--
作者：
Bohlen, L.;Dale, A. W.;Wallmann, K.
沿沿着6个站位调查了秘鲁最低含氧量带（OMZ）的底栖氮循环。一个广泛的数据集，包括孔隙水浓度剖面和原位底栖通量的硝酸盐（NO3-），亚硝酸盐（NO2-）和铵（NH 4+）被用来约束1-D的反应传输模型，旨在模拟和解释在每个站的测量数据。模拟速率硝化，反硝化，厌氧氨氧化和异化硝酸盐还原铵（DNRA）的丝状大型硫细菌（如Beggiatoa和Thioploca）是高度可变的整个OMZ，但明确的趋势是可辨别的。在大陆架和上斜坡（80 - 260米水深），其中广泛的地区的细菌垫，DNRA占主导地位的总氮周转（= 65%的NO3- + NO2-吸收的沉积物从底层水。尽管如此，这些沉积物并不代表溶解无机氮（DIN = NO3- + NO2- + NH 4+）的主要汇，因为DNRA将NO3-和潜在的NO2-还原为NH 4+。因此，陆架和上斜坡沉积物的DIN回收网站由于相对较低的反硝化速率和高速率的铵释放DNRA和氨化的有机质。这一发现与目前的观点，即沉积物下OMZ是一个强大的汇DIN。只有在更大的水深（300-1000米），沉积物才成为DIN的净汇。反硝化作用是主要的过程（62 mmol Nm（-2）d（-1）），去除了沉积物中55-73%的NO3-和NO2-，DNRA和厌氧氨氧化占剩余部分。厌氧氨氧化是次要的货架和上斜坡，但贡献了62%的总N-2生产在1000米站。结果表明，分区的氧化N（NO3，NO2）到DNRA或反硝化作用是一个关键因素，决定作用的海洋沉积物DIN汇或回收网站。因此，高测量的氧化氮内OMZ的底栖生物吸收率并不一定表明从海洋环境中的固定氮的损失。(C)2011爱思唯尔有限公司版权所有。
Benthic nitrogen (N) cycling was investigated at six stations along a transect traversing the Peruvian oxygen minimum zone (OMZ) at 11 degrees S. An extensive dataset including porewater concentration profiles and in situ benthic fluxes of nitrate (NO3-), nitrite (NO2-) and ammonium (NH4+) was used to constrain a 1-D reaction-transport model designed to simulate and interpret the measured data at each station. Simulated rates of nitrification, denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) by filamentous large sulfur bacteria (e.g. Beggiatoa and Thioploca) were highly variable throughout the OMZ yet clear trends were discernible. On the shelf and upper slope (80 260 m water depth) where extensive areas of bacterial mats were present, DNRA dominated total N turnover (= 65% of NO3- + NO2- uptake by the sediments from the bottom water. Nonetheless, these sediments did not represent a major sink for dissolved inorganic nitrogen (DIN = NO3- + NO2- + NH4+) since DNRA reduces NO3- and, potentially NO2-, to NH4+. Consequently, the shelf and upper slope sediments were recycling sites for DIN due to relatively low rates of denitrification and high rates of ammonium release from DNRA and ammonification of organic matter. This finding contrasts with the current opinion that sediments underlying OMZs are a strong sink for DIN. Only at greater water depths (300-1000 m) did the sediments become a net sink for DIN. Here, denitrification was the major process (62 mmol N m(-2) d(-1)) and removed 55-73% of NO3- and NO2- taken up by the sediments, with DNRA and anammox accounting for the remaining fraction. Anammox was of minor importance on the shelf and upper slope yet contributed up to 62% to total N-2 production at the 1000 m station. The results indicate that the partitioning of oxidized N (NO3, NO2) into DNRA or denitrification is a key factor determining the role of marine sediments as DIN sinks or recycling sites. Consequently, high measured benthic uptake rates of oxidized N within OMZs do not necessarily indicate a loss of fixed N from the marine environment. (C) 2011 Elsevier Ltd. All rights reserved.