Reduced sulfur species (RSS) are involved in essential biological and chemical processes, including metal complexation, yet little is known about their occurrence and behaviour in marine systems. Here, we present a quantitative and qualitative data set of species-specific RSS in open ocean samples collected during the GEOTRACES Tonga GPpr14 cruise. The cruise traversed differing biogeochemical provinces, from the mesotrophic Melanesian waters and the North Fiji Basin, through the hydrothermally active Lau Basin, eastward to the oligotrophic South Pacific Gyre. Using cathodic stripping voltammetry in acidified samples (pH 2), we measured the concentration of two RSS, with peak potentials of -0.18 and -0.09 V in equivalents of thioacetamide (TA) and glutathione (GSH) respectively. GSH-like compounds were only present in the upper 200 m at concentrations up to 6.2 nM eq. GSH, consistent with other cathodic stripping voltammetry as well as chromatography-based studies. In contrast, RSS−0.18 V2 compounds were detected at all depths at concentrations ranging from 48 nM to 980 nM eq. TA. Both RSS−0.18 V2 and GSH-like compounds were present at higher levels in the hydrothermally-impacted region of the Lau Basin relative to other stations. The highest levels, along with high sulfide concentrations, were detected in a hydrothermal plume sample, indicating that hydrothermal vents are a direct or indirect source of these compounds. Elevated levels of RSS−0.18 V2 compounds were detected throughout almost the entire water column at a station located in the North Fiji Basin. We also employed the qualitative technique of cathodic pseudopolarography on unbuffered samples (pH ~ 8.5). Pseudopolarograms of marine RSS were compared to sulfide, GSH and TA standards. Pseudopolarography supports the presence of GSH in marine samples. However, while a compound that is electrochemically similar to TA is often detected in marine samples, TA itself is not thought to be naturally present. This is supported by our pseudopolarograms of RSS−0.52 V8.5 which often lacked the characteristic TA reduction wave but suggested the presence of other unidentified RSS compounds.

中文翻译：

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还原硫物质在西热带南太平洋贫营养和热液水域中的分布和行为


还原硫物质 （RSS） 参与基本的生物和化学过程，包括金属络合，但人们对它们在海洋系统中的出现和行为知之甚少。在这里，我们展示了在 GEOTRACES Tonga GPpr14 巡航期间收集的公海样本中物种特异性 RSS 的定量和定性数据集。这次巡航穿越了不同的生物地球化学省份，从中营养的美拉尼西亚水域和北斐济盆地，穿过热液活跃的劳盆地，向东到达贫营养的南太平洋环流。在酸化样品 （pH 2） 中使用阴极溶出伏安法，我们测量了两种 RSS 的浓度，在硫代乙酰胺 （TA） 和谷胱甘肽 （GSH） 当量中的峰电位分别为 -0.18 和 -0.09 V。GSH 样化合物仅以高达 6.2 nM 当量 GSH 的浓度存在于上部 200 m，与其他阴极溶出伏安法以及基于色谱的研究一致。相比之下，在所有深度检测到 RSS −0.18 V2 化合物，浓度范围为 48 nM 至 980 nM 当量 TA。相对于其他站点，RSS−0.18 V2 和 GSH 样化合物在 Lau 盆地热液影响区域的含量较高。在热液羽流样本中检测到最高水平和高硫化物浓度，表明热液喷口是这些化合物的直接或间接来源。在位于斐济北部盆地的一个站点，几乎在整个水柱中检测到 RSS−0.18 V2 化合物的水平升高。我们还在无缓冲样品 （pH ~ 8.5） 上采用了阴极伪极谱法的定性技术。将海洋 RSS 的伪极谱图与硫化物、 GSH 和 TA 标准品进行比较。 假极谱法支持海洋样品中存在 GSH。然而，虽然在海洋样品中经常检测到电化学上与 TA 相似的化合物，但 TA 本身并不被认为天然存在。我们的 RSS-0.52 V8.5 伪极谱图支持了这一点，该极谱图通常缺乏特征性的 TA 还原波，但表明存在其他未识别的 RSS 化合物。