Max Planck Institute for Marine Microbiology, Bremen, Germany.
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
Nat Commun. 2023 Oct 16;14(1):6529. doi: 10.1038/s41467-023-42304-4.
Methylphosphonate is an organic phosphorus compound used by microorganisms when phosphate, a key nutrient limiting growth in most marine surface waters, becomes unavailable. Microbial methylphosphonate use can result in the formation of methane, a potent greenhouse gas, in oxic waters where methane production is traditionally unexpected. The extent and controlling factors of such aerobic methane formation remain underexplored. Here, we show high potential net rates of methylphosphonate-driven methane formation (median 0.4 nmol methane L d) in the upper water column of the western tropical North Atlantic. The rates are repressed but still quantifiable in the presence of in-situ or added phosphate, suggesting that some methylphosphonate-driven methane formation persists in phosphate-replete waters. The genetic potential for methylphosphonate utilisation is present in and transcribed by key photo- and heterotrophic microbial taxa, such as Pelagibacterales, SAR116, and Trichodesmium. While the large cyanobacterial nitrogen-fixers dominate in the surface layer, phosphonate utilisation by Alphaproteobacteria appears to become more important in deeper depths. We estimate that at our study site, a substantial part (median 11%) of the measured surface carbon fixation can be sustained by phosphorus liberated from phosphonate utilisation, highlighting the ecological importance of phosphonates in the carbon cycle of the oligotrophic ocean.
甲基膦酸酯是一种有机磷化合物，当磷酸盐（一种限制大多数海洋表面水域中生物生长的关键营养物质）变得不可用时，微生物会使用它。在传统上预期不会产生甲烷的含氧水中，微生物利用甲基膦酸酯会导致甲烷的形成，甲烷是一种强效温室气体。这种有氧甲烷形成的程度和控制因素仍未得到充分探索。在这里，我们显示了在北大西洋西部热带海域上层水体中，甲基膦酸酯驱动的甲烷形成具有很高的净潜在速率（中位数为 0.4 nmol 甲烷 L d）。在原位或添加磷酸盐的存在下，这些速率受到抑制但仍然可以量化，这表明在富含磷酸盐的水中仍然存在一些由甲基膦酸酯驱动的甲烷形成。利用甲基膦酸酯的遗传潜力存在于并由关键的光和异养微生物类群转录，如 Pelagibacterales、SAR116 和 Trichodesmium。虽然大型蓝藻固氮生物在表层占主导地位，但在更深的深度，α变形菌利用膦酸盐似乎变得更加重要。我们估计，在我们的研究地点，通过利用膦酸盐释放的磷，可以维持所测量的表层碳固定的很大一部分（中位数为 11%），这突出了膦酸盐在贫营养海洋碳循环中的生态重要性。
