The low‐molecular‐weight (LMW) reduced sulfur substances (RSS) composition of dissolved organic matter (DOM) was examined along the GEOTRACES US‐GP15 section in the Pacific Ocean. We demonstrate that LMW RSS constitutes a significant fraction of nonvolatile dissolved organic sulfur (DOS). While thiols such as glutathione were below our detection limit (300 pM), RSS containing two carbon (C) sulfur (S) bonds were present at concentrations in the hundreds of nM range. RSS accumulation was observed in subtropical waters. The most likely source of these RSS is microbial alteration of sulfurized DOM with production of secondary thioamidated metabolites. RSS are initially produced by cyanobacteria to mitigate copper and oxidative stress induced by UV‐B irradiance. A preferential remineralization of RSS over dissolved organic carbon (DOC) in the upper 350 m suggests a partial lability of LMW DOS. Deeper, homogeneous concentrations and C : S ratio indicate increasing stability of this LMW DOS.

中文翻译：

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低分子量还原硫物质：太平洋中非挥发性溶解有机硫的主要成分


沿太平洋 GEOTRACES US-GP15 剖面检查了溶解有机物 (DOM) 的低分子量 (LMW) 还原硫物质 (RSS) 组成。我们证明 LMW RSS 构成了非挥发性溶解有机硫 (DOS) 的很大一部分。虽然谷胱甘肽等硫醇低于我们的检测限 (300 pM)，但含有两个碳 (C) 硫 (S) 键的 RSS 的浓度在数百 nM 范围内。在亚热带水域观察到RSS积累。这些 RSS 最可能的来源是硫化 DOM 的微生物改变，并产生次级硫代酰胺化代谢物。 RSS 最初由蓝细菌产生，用于减轻 UV-B 辐照度引起的铜和氧化应激。在 350 m 上部，RSS 比溶解有机碳 (DOC) 优先再矿化，表明 LMW DOS 部分不稳定。更深、更均匀的浓度和 C:S 比率表明该 LMW DOS 的稳定性不断增强。