In aquatic ecosystems, dissolved organic matter (DOM) plays a vital role in microbial communities and the biogeochemical cycling of elements. However, little is known about the associations between DOM and microbial communities in lake sediments. This study investigated the composition of water-extractable organic matter and microbial communities in surface sediments of lakes with different salinities on the Qinghai-Tibet Plateau. Ultrahigh-resolution mass spectrometry and high-throughput microbial sequencing techniques were employed to assess the associations between molecular diversity and microbial diversity and the effects of salinity in 19 lakes spanning a salinity range from 0.22 ‰ to 341.87 ‰. Our results show that increasing salinity of lake water led to higher molecular diversity of DOM in surface sediments. High-salinity lakes exhibited distinct DOM characteristics, such as lower aromaticity, smaller molecular weight, and higher oxidation degree, compared to freshwater lakes. The complexity of the microbial network composition of sediments first increased and then decreased with the increase of salinity. Moreover, as salinity increases, the dominant species transitioned from Gammaproteobacteria to Bacteroidia, and this transition was accompanied by a decrease in microbial diversity and an increase in molecular diversity. Microbial factors accounted for 34.68 % of the variation in the molecular composition of DOM. Overall, this study emphasizes the significant effects of salinity on both molecular and microbial diversity in lake sediments. Furthermore, our findings underscore the importance of microbes in controlling the range of organic compounds present in lakes and deepen our knowledge of the biogeochemical cycling of DOM.

中文翻译：

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青藏高原湖泊沉积物中溶解有机物与微生物群落之间的强关联取决于盐度

在水生生态系统中，溶解有机物（DOM）在微生物群落和元素的生物地球化学循环中发挥着至关重要的作用。然而，人们对 DOM 与湖泊沉积物中微生物群落之间的关系知之甚少。本研究调查了青藏高原不同盐度湖泊表层沉积物中水可提取有机质和微生物群落的组成。采用超高分辨率质谱和高通量微生物测序技术评估了分子多样性和微生物多样性之间的关联以及盐度对盐度范围从0.22‰到341.87‰的19个湖泊的影响。我们的结果表明，湖水盐度的增加导致表层沉积物中 DOM 的分子多样性更高。与淡水湖相比，高盐度湖泊表现出明显的 DOM 特征，例如较低的芳香度、较小的分子量和较高的氧化度。沉积物微生物网络组成的复杂性随着盐度的增加先增加后减少。此外，随着盐度的增加，优势菌种从Gammaproteobacteria转变为Bacteroidia，这种转变伴随着微生物多样性的减少和分子多样性的增加。微生物因素造成DOM分子组成变异的34.68%。总的来说，这项研究强调了盐度对湖泊沉积物分子和微生物多样性的显着影响。此外，我们的研究结果强调了微生物在控制湖泊中存在的有机化合物范围方面的重要性，并加深了我们对 DOM 生物地球化学循环的了解。