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Effects of Drought-Rewetting Process and Salinity Variations on Dissolved Organic Matter Transformation and its Bacterial Mechanisms in Lacustrine Pore Water

2022; RELX Group (Netherlands); Linguagem: Inglês

10.2139/ssrn.4223068

1556-5068

Xiang Zhu, Lei Xie, Yushen Ma, Longmian Wang, Qingqing Pang, Fuquan Peng, Zhipeng Xu, Bin Xu, Fei He, Lixiao Ni,

Hydrocarbon exploration and reservoir analysis

Climate change and anthropogenic activities cause salinity fluctuations and frequent drought-rewetting process in lacustrine littoral zones. However, the synergistic effects of these processes on the quality, quantity, and bacterial mechanisms of dissolved organic matter (DOM) in pore water are not well understood. An experiment was conducted to analyze the influence of drought-rewetting processes and salinity variations on DOM characteristics and the resident bacterial communities. The results showed that higher salinity (6,000 mg/L) resulted in a higher humification index (HIX), lower spectral slope ratio (S R ), E2/E3, and biological index (BIX) of pore water, and an accelerated degradation of protein-like substances. The dominant DOM fluorescent components were protein-like substances before the drought-rewetting process, which changed to humic-like substances after the drought-rewetting process. The synergistic effects of higher salinity and drought-rewetting process were to retain more humified, more aromatic, and less bioavailable DOM in the pore water, to maintain lower concentrations of pore water DOM, and to increase the dominance of autotrophic bacteria, such as the Thiobacillus belong to Hydrogenophilaceae. Before the drought-rewetting process Hydrogenophilaceae, Oxalobacteraceae, and Flavobacteriaceae participated in the DOM transformation, while after the drought-rewetting process, the Hydrogenophilaceae, Desulfobacteraceae, Anaerolineacea, Planococcaceae, and Clostridiaceae were associated with the DOM components. Hydrogenophilaceae, Desulfobacteraceae, and Anaerolineacea were resistant to increased salinity, but other functional bacteria were negatively correlated with salinity. The drought-rewetting process greatly reduced the compactness of interrelationships among the bacteria and altered interactions between Hydrogenophilaceae and other bacteria. Continuous recharge of water with appropriate salinity and flow instead of intermittent recharge to brackish lakes can keep water levels and salinity stable, which may be beneficial for maintaining the stability of the ecosystem and carbon cycling.