Stephens Brandon M, Stincone Paolo, Petras Daniel, English Chance J, Opalk Keri, Giovannoni Stephen, Carlson Craig A
Marine Science Institute/Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA.
Institute of Oceanography, National Taiwan University, Taipei, Taiwan.
Commun Biol. 2025 Jan 29;8(1):145. doi: 10.1038/s42003-025-07574-2.
Oxygen consumption by oceanic microbes can predict respiration (CO production) but requires an assumed respiratory quotient (RQ; ΔO/ΔCO). Measured apparent RQs (ARQs) can be impacted by various processes, including nitrification and changes in dissolved organic matter (DOM) composition, leading to discrepancies between ARQ and actual RQ. In DOM remineralization experiments conducted in the eastern North Atlantic Ocean, ARQs averaged 1.39 ± 0.14, similar to predictions for complete consumption of plankton biomass. DOM removed with an elevated nominal oxidation state (i.e., more oxidized DOM), as detected by liquid chromatography-tandem mass spectrometry, coincided with increased hydrolyzable amino acid removal, increased ARQs and bacterioplankton respiration (BR), and a decreased bacterioplankton growth efficiency (BGE). Across experiments, evidence emerged that nitrification and DOM partial oxidation, driven in part by bacterioplankton members of OM43, SAR92 and Rhodobacteraceae, can elevate BR relative to bacterioplankton consumption of plankton-derived carbon. These rare synoptic measurements of interrelated variables reveal complex biochemical and cellular processes underlying variability in large-scale CO production estimates.
海洋微生物的耗氧量可预测呼吸作用（二氧化碳产生量），但这需要假定一个呼吸商（RQ；ΔO₂/ΔCO₂）。实测的表观呼吸商（ARQ）可能会受到各种过程的影响，包括硝化作用和溶解有机物（DOM）组成的变化，从而导致ARQ与实际RQ之间存在差异。在北大西洋东部进行的DOM再矿化实验中，ARQ的平均值为1.39±0.14，与浮游生物量完全消耗的预测值相似。通过液相色谱-串联质谱法检测到，去除的DOM具有较高的标称氧化态（即氧化程度更高的DOM），这与可水解氨基酸去除量增加、ARQ和浮游细菌呼吸作用（BR）增加以及浮游细菌生长效率（BGE）降低相吻合。在所有实验中，有证据表明，部分由OM43、SAR92和红杆菌科的浮游细菌成员驱动的硝化作用和DOM部分氧化作用，相对于浮游细菌对浮游生物衍生碳的消耗，可提高BR。这些对相互关联变量的罕见的综合测量揭示了大规模二氧化碳产生量估计值变化背后复杂的生化和细胞过程。
