Seasonality of water column methane oxidation and deoxygenation in a dynamic marine environment
Seasonality of water column methane oxidation and deoxygenation in a dynamic marine environment
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动态海洋环境中水柱甲烷氧化和脱氧的季节性
DOI：
10.1016/j.gca.2022.09.017
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发表时间：
2022
影响因子：
5
通讯作者：
Valentine, David L.
中科院分区：
文献类型：
--
作者：
Qin, Qianhui;Kinnaman, Franklin S.;Gosselin, Kelsey M.;Liu, Na;Treude, Tina;Valentine, David L.
进入世界海洋的甲烷大部分被沉积物和上覆水柱中的微生物拦截，并在有机会到达大气层之前被氧化，成为温室气体。控制海洋中甲烷消耗的因素尚未得到很好的确定，其在动态海洋环境中的生物地球化学研究不足，部分原因是捕获空间和时间变化方面的挑战。我们的研究集中在动态海洋环境中的甲烷的地球化学结构的因素，圣巴巴拉盆地。圣巴巴拉盆地的深水柱经历了季节性的氧损失和间歇性的补充，我们发现这是构造甲烷积累和微生物消耗甲烷的速率的主要因素。我们发现，通常在整个夏天氧气的逐渐减少，在秋天的水柱中甲烷的明显积累达到顶峰。甲烷氧化率在夏季保持较低，在秋季随着甲烷的积累而增加，即使在甲烷浓度下降后，到春季仍保持较高水平。然而，甲烷氧化动力学实验的结果显示，零级动力学依赖于氧浓度，表明在生态系统尺度上，氧气对甲烷氧化的影响可能是间接的。我们还捕捉到了一个明显的混合事件，在秋季驱动空间和时间的变化，在圣巴巴拉盆地的氧气，硝酸盐和甲烷浓度，在调查的时间尺度为8天和沿着等深线在7公里的空间尺度上的鲜明变化。总的来说，这些结果表明与限制循环相关的甲烷营养群落的季节性发展和衰减，但也是以前没有意识到这种环境的时空变化。
Most of the methane input to the world’s oceans is intercepted by microorganisms in sediment and the overlying water column and oxidized before it has an opportunity to reach the atmosphere, where it acts as a greenhouse gas. The factors controlling methane consumption in the ocean are not well established and its biogeochemistry in dynamic marine environments is understudied in-part because of challenges in capturing spatial and temporal variability. Our study focused on the factors that structure methane’s biogeochemistry in a dynamic marine environment, the Santa Barbara Basin. The deep-water column of the Santa Barbara Basin experiences seasonal oxygen loss and episodic replenishment which we found to be major factors in structuring the accumulation of methane and the rate at which microorganisms consumed that methane. We found the gradual decline in oxygen that commonly occurs through the summer culminated with a pronounced accumulation of methane in the water column during the fall. Rates of methane oxidation remained low in summer, increased with the buildup of methane in fall, and remained elevated into spring, even after methane concentration had declined. However, results from methane oxidation kinetics experiments revealed a zero-order kinetic dependence on oxygen concentration, indicating that oxygen’s effect on methanotrophy at the ecosystem scale is likely indirect. We also captured an apparent mixing event during fall that drove spatial and temporal variability in oxygen, nitrate and methane concentrations in the Santa Barbara Basin, with stark variations at the investigated timescale of 8 days and along isobaths at a spatial scale of 7 km. Collectively, these results indicate the seasonal development and attenuation of a methanotrophic community associated with restricted circulation, but also of a spatiotemporal variability not previously appreciated for this environment.