Abstract：
The characteristics of lake dissolved organic matter (DOM) pool and lake ecosystem interact, and studying the responses between sediment DOM characteristics and lake ecosystem changes may shed light on the inherent connection between ecosystem evolution and carbon biogeochemical cycles. Lakes in cold and arid regions are sensitive to changes and accumulate large amounts of carbon as DOM, which may provide a window into more explicit relationships between ecosystem evolution and changes in sediment DOM characteristics in time dimension. However, considerable blind spots exist in the responses between the sediment DOM and ecosystem evolution on time scale and the underlying mechanisms. In this study, multiple approaches were combined to investigate the relationship between the variation trend of sediment DOM characteristics and the evolution of fragile lake ecosystems across three different lake ecosystems in cold and arid regions of China. A strong positive relationship between sediment DOM stabilities, especially humification, and ecosystem degradation was found, consistent for the three lakes. Ultra-high-resolution mass spectrometry and structural equation modeling revealed that the changes of ecosystems affected sediment DOM stability through direct pathways (0.24), such as the contents of terrestrial DOM in lake DOM pool, and indirect pathways, including algae-mediated (0.43) and salinity-mediated pathways (0.22), which all increased the contents of refractory DOM in the lake DOM pool and sediments. Based on the fact that DOM stability changes could act on the ecosystem in turn, a possible positive feedback mechanism between ecosystem degradation and increased DOM stability was further inferred. These results suggested that the continuous increased stability of sediment DOM in may implies ecosystem degradation of lakes in the cold and arid regions. This study provides a new perspective for recognizing ecosystem evolution through sediment DOM and improves the understanding of the interaction of lake ecosystem evolution and the biogeochemical cycle of DOM.
摘要：
湖泊溶解有机质(DOM)池与湖泊生态系统相互作用的特征,研究沉积物DOM特征与湖泊生态系统变化之间的响应，可以揭示生态系统演化与碳生物地球化学循环之间的内在联系。寒冷和干旱地区的湖泊对变化敏感，积累了大量的碳作为DOM，这可能为生态系统演化与时间维度上沉积物DOM特征变化之间的更明确关系提供了一个窗口。然而,在时间尺度上，沉积物DOM与生态系统演化之间的响应和潜在机制存在相当大的盲点。在这项研究中,结合多种方法，研究了中国寒冷干旱区三种不同湖泊生态系统沉积物DOM特征的变化趋势与脆弱湖泊生态系统演变之间的关系。沉积物DOM稳定性之间有很强的正相关关系，尤其是羞辱，发现了生态系统退化，这三个湖泊是一致的。超高分辨率质谱和结构方程模型表明，生态系统的变化通过直接途径（0.24）影响沉积物DOM的稳定性，例如DOM湖池中的陆地DOM的内容，和间接途径，包括藻类介导的途径(0.43)和盐度介导的途径(0.22)，所有这些都增加了湖泊DOM池和沉积物中难处理DOM的含量。基于DOM稳定性变化可以反过来作用于生态系统的事实，进一步推断了生态系统退化与DOM稳定性增强之间可能的正反馈机制。这些结果表明，DOM中沉积物稳定性的持续增加可能意味着寒冷干旱地区湖泊的生态系统退化。该研究为通过沉积物DOM识别生态系统演化提供了新的视角，提高了对湖泊生态系统演化与DOM生物地球化学循环相互作用的认识。
