Life and Environmental Sciences, University of California, Merced, Merced, CA, USA.
Scripps Institution of Oceanography, University of California, San Diego, CA, USA.
Nat Commun. 2021 Dec 2;12(1):7043. doi: 10.1038/s41467-021-27381-7.
Oceanic oxygen minimum zones (OMZs) are globally significant sites of biogeochemical cycling where microorganisms deplete dissolved oxygen (DO) to concentrations <20 µM. Amid intense competition for DO in these metabolically challenging environments, aerobic nitrite oxidation may consume significant amounts of DO and help maintain low DO concentrations, but this remains unquantified. Using parallel measurements of oxygen consumption rates and N-nitrite oxidation rates applied to both water column profiles and oxygen manipulation experiments, we show that the contribution of nitrite oxidation to overall DO consumption systematically increases as DO declines below 2 µM. Nitrite oxidation can account for all DO consumption only under DO concentrations <393 nM found in and below the secondary chlorophyll maximum. These patterns are consistent across sampling stations and experiments, reflecting coupling between nitrate reduction and nitrite-oxidizing Nitrospina with high oxygen affinity (based on isotopic and omic data). Collectively our results demonstrate that nitrite oxidation plays a pivotal role in the maintenance and biogeochemical dynamics of OMZs.
海洋缺氧区（OMZs）是全球范围内具有重要意义的生物地球化学循环场所，微生物会将溶解氧（DO）消耗至<20 μM 以下。在这些代谢极具挑战性的环境中，由于对 DO 的激烈竞争，好氧亚硝酸盐氧化可能会消耗大量 DO，并有助于维持低 DO 浓度，但这一点尚未得到量化。我们通过对水柱剖面和 DO 操纵实验进行氧消耗率和 N-亚硝酸盐氧化率的平行测量，表明亚硝酸盐氧化对总 DO 消耗的贡献随着 DO 下降至 2 μM 以下而系统增加。只有在 secondary chlorophyll maximum 及其以下发现的 393 nM 以下的 DO 浓度下，亚硝酸盐氧化才能完全消耗 DO。这些模式在采样站和实验中是一致的，反映了具有高氧气亲和力的硝酸盐还原和亚硝酸盐氧化菌 Nitrospina 之间的耦合（基于同位素和组学数据）。总的来说，我们的结果表明，亚硝酸盐氧化在 OMZs 的维持和生物地球化学动态中起着关键作用。
