近日，美国加州大学圣芭芭拉分校Barbara Bayer团队研究了氨氧化剂对海洋中无机碳固定的微小贡献。2025年9月23日出版的《自然—地球科学》杂志发表了这项成果。

氨氧化古细菌是海洋中最丰富的化能岩石自养生物，并且被认为主导了阳光照射的表层以下的碳固存。然而，通过下沉的颗粒有机质从表面输送的还原性氮的供应不足以支持在暗海洋中维持测量的碳固定率所需的硝化量。

研究组试图通过量化氨氧化剂对热带东部和亚热带太平洋暗碳固定的贡献来调和这一观察到的差异。他们使用苯乙炔（一种氨单加氧酶的特异性抑制剂），选择性地抑制整个水柱(60-600米深度)。结果发现，尽管氨氧化剂的丰度很高，但它们对暗碳固定的贡献很小，在中上层区域(120-175米深度）占热带太平洋东部总深度整合率的4-25%。在某些站点，氨氧化可占暗碳固定的50%左右。该研究结果挑战了目前认为暗海洋中的碳固定主要由硝化维持的观点，并表明其他微生物代谢，包括异养，可能比以前认为的起更大的作用。

附：英文原文

Title: Minor contribution of ammonia oxidizers to inorganic carbon fixation in the ocean

Author: Bayer, Barbara, Kitzinger, Katharina, Paul, Nicola L., Albers, Justine B., Saito, Mak A., Wagner, Michael, Carlson, Craig A., Santoro, Alyson E.

Issue&Volume: 2025-09-23

Abstract: Ammonia-oxidizing archaea are the most abundant chemolithoautotrophs in the ocean and are assumed to dominate carbon fixation below the sunlit surface layer. However, the supply of reduced nitrogen delivered from the surface in sinking particulate organic matter is insufficient to support the amount of nitrification required to sustain measured carbon fixation rates in the dark ocean. Here we attempt to reconcile this observed discrepancy by quantifying the contribution of ammonia oxidizers to dark carbon fixation in the eastern tropical and subtropical Pacific Ocean. We used phenylacetylene—a specific inhibitor of the ammonia monooxygenase enzyme—to selectively inhibit ammonia oxidizers in samples collected throughout the water column (60–600m depth). We show that, despite their high abundances, ammonia oxidizers contribute only a small fraction to dark carbon fixation, accounting for 4–25% of the total depth-integrated rates in the eastern tropical Pacific. The highest contributions were observed within the upper mesopelagic zone (120–175m depth), where ammonia oxidation could account for ~50% of dark carbon fixation at some stations. Our results challenge the current view that carbon fixation in the dark ocean is primarily sustained by nitrification and suggest that other microbial metabolisms, including heterotrophy, might play a larger role than previously assumed.

DOI: 10.1038/s41561-025-01798-x

Source: https://www.nature.com/articles/s41561-025-01798-x