Effects of drought-rewetting process and salinity variations on DOM transformation and bacterial communities in lacustrine sediments

Abstract

Abstract Climate change and anthropogenic activities cause salinity fluctuations and frequent drought-rewetting process in lacustrine littoral zones. However, joint effects of these processes on quality and quantity of dissolved organic matter (DOM) in pore water and bacterial communities in sediments are not well understood. An experiment was conducted to attempt to fill the above gaps, the results showed that the joint effects of higher salinity (6,000 mg/L) and drought-rewetting process were to retain more humified, more aromatic, and less bioavailable DOM, and to maintain lower DOM concentrations in pore water. The drought-rewetting process magnified influence of salinity on bacterial communities. Before the drought-rewetting process, Hydrogenophilaceae, Oxalobacteraceae, and Flavobacteriaceae participated in the DOM transformation, while Hydrogenophilaceae, Desulfobacteraceae, Anaerolineacea, Planococcaceae, and Clostridiaceae were associated with DOM components after this process. The drought-rewetting process greatly increased significant positive correlations (P<0.05) among bacteria, which was consistent with Stress Gradient Hypothesis and destabilized the bacterial communities. Higher (6,000 mg/L) or lower (1,200 mg/L) salinity were all not conducive to stability of bacterial communities in Shahu Lake. The results of this study may provide ideas for further investigating DOM transformation and cycling in brackish-water lakes.