Depth-resolved photochemical lability of dissolved organic matter in the western tropical Pacific Ocean
Depth-resolved photochemical lability of dissolved organic matter in the western tropical Pacific Ocean
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西热带太平洋溶解有机物的深度分辨光化学不稳定性
DOI：
10.1029/2019jg005425
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发表时间：
2020
影响因子：
3.7
通讯作者：
Huixiang Xie
中科院分区：
文献类型：
--
作者：
Fangming Yang;Guisheng Song;Phillippe Massicotte;Hao Wei;Huixiang Xie
从南中国和菲律宾近海不同深度采集的水样被暴露在太阳模拟辐射中。在所有样品中都观察到了溶解有机碳(DOC)的光矿化和发色溶解有机物(CDOM)及其类腐殖质荧光成分(FDOM)的光漂白。然而，类蛋白质的FDOM要么是光解的，要么是光产生的，这取决于样品的深度。CDOM和类腐殖质FDOM在深水中的光漂白速度远快于浅水，而光矿化表现出较弱的垂直分带性。接种地表水细菌的辐照深水对DOC的去除有明显的促进作用，但对CDOM的产生有一定的促进作用。这项研究的结果表明，深海CDOM和FDOM在一个海洋混合周期内只能勉强存活于光漂白，但生物难降解的深层DOC的光化学周转率比其平均放射性碳年龄要长得多。光化学-微生物耦合过程不仅可以去除部分难生物降解的深层DOM，而且可以在海洋翻转循环过程中再生部分DOM。
Water samples collected from various depths of the offshore South China and Philippine Seas were exposed to solar‐simulated radiation. Photomineralization of dissolved organic carbon (DOC) and photobleaching of chromophoric dissolved organic matter (CDOM) and its humic‐like fluorescent constituent (FDOM) were observed in all samples. Protein‐like FDOM was, however, either photo‐decomposed or photo‐produced, depending on the sample's depth. The photobleaching of CDOM and humic‐like FDOM was much faster in deep than in shallow water samples while photomineralization displayed a weaker vertical zonation. Prior‐irradiated deep water inoculated with surface‐water bacteria showed enhanced microbial DOC removal but CDOM production. Results from this study suggest that deep‐ocean CDOM and FDOM can barely survive photobleaching during one ocean mixing cycle, but photochemical turnover of the bio‐refractory deep DOC is considerably longer than its average radiocarbon age. Coupled photochemical‐microbial processes can not only remove part of the bio‐refractory deep DOM but also regenerate part of it during ocean overturning circulation.