Institute for Advance Marine Research, China University of Geosciences, Guangzhou 511462, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China; Institute of Marine Science and Technology, Shandong University, Qingdao 266237, China.
Institute for Advance Marine Research, China University of Geosciences, Guangzhou 511462, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
Mar Pollut Bull. 2023 Jul;192:114985. doi: 10.1016/j.marpolbul.2023.114985. Epub 2023 May 9.
Marine dissolved organic matter (DOM) plays an important role in aquatic ecosystems and is an essential reservoir of organic carbon in the marine carbon cycle. In this study, seawater DOM samples from 33 stations were collected in spring 2022 (April to May, 20 stations) and autumn 2020 (October to November, 13 stations) to better characterize and compare DOM variability within 200 m water layer in the eastern Indian Ocean (EIO). Hydrological parameters, nutrients and spectroscopic indices were calculated and evaluated for two cruises. In addition, excitation emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC) was used to directly analyse seawater DOM samples. The sources and processes of DOM in the EIO were assessed by fluorescence index (FI), freshness index (β/α), Biological index (BIX), and humification index (HIX). Three fluorescent components were identified in DOM samples from two cruises, including: C1 (tryptophan- and tyrosine-like), C2 (marine and/or terrestrial humic-like), and C3 (terrestrial humic-like). The components of C1 accounted for 39.45 % ± 8.79 %, C2 for 33.05 % ± 6.42 %, and C3 for 27.20 % ± 4.47 % within 200 m water layer. The intensity of the DOM fluorescence seems to varied due to seasonal differences. In particular, the source of the DOM fraction varied at <100 m layer, which may also be related to the structure of the microbial community. Further, there is a strong correlation between the depth of seawater and hydrographic parameters, fluorescence indices and fluorescence components. Nutrients (nitrate, dissolved inorganic phosphate, and dissolved silicate) and humic-like fractions are more likely to accumulate in the deeper layers of the ocean. Thus, these results provide some data support for the variability of DOM fractions on a vertical scale in the EIO.
海洋溶解有机质（DOM）在水生生态系统中起着重要作用，是海洋碳循环中有机碳的重要储存库。本研究于 2022 年春季（4 月至 5 月，20 站）和 2020 年秋季（10 月至 11 月，13 站）采集了东印度洋（EIO）200 m 水层内海水 DOM 样品，以更好地描述和比较 DOM 的变异性。为两次航行计算和评估了水文参数、营养物质和光谱指数。此外，还使用激发发射矩阵光谱学结合平行因子分析（EEM-PARAFAC）直接分析海水 DOM 样品。通过荧光指数（FI）、新鲜度指数（β/α）、生物指数（BIX）和腐殖化指数（HIX）评估了 EIO 中 DOM 的来源和过程。在两次航行的 DOM 样品中鉴定出三种荧光组分，包括：C1（色氨酸和酪氨酸样）、C2（海洋和/或陆地腐殖质样）和 C3（陆地腐殖质样）。C1 组分占 200 m 水层内 39.45%±8.79%，C2 组分占 33.05%±6.42%，C3 组分占 27.20%±4.47%。DOM 荧光强度似乎因季节差异而变化。特别是在<100 m 层，DOM 组分的来源发生了变化，这也可能与微生物群落的结构有关。此外，海水深度与水文参数、荧光指数和荧光组分之间存在很强的相关性。营养物质（硝酸盐、溶解无机磷酸盐和溶解硅酸盐）和类腐殖质物质更有可能在海洋的较深层积累。因此，这些结果为 EIO 中 DOM 分数在垂直尺度上的变异性提供了一些数据支持。
