Spatio-temporal variations of activity of nitrate-driven anaerobic oxidation of methane and community structure of Candidatus Methanoperedens-like archaea in sediment of Wuxijiang river

Abstract

Nitrate-driven anaerobic oxidation of methane (AOM), catalyzing by Candidatus Methanoperedens-like archaea, is a new addition in the global CH4 cycle. This AOM process acts as a novel pathway for CH4 emission reduction in freshwater aquatic ecosystems; however, its quantitative importance and regulatory factors in riverine ecosystems are nearly unknown. Here, we examined the spatio-temporal changes of the communities of Methanoperedens-like archaea and nitrate-driven AOM activity in sediment of Wuxijiang River, a mountainous river in China. These archaeal community composition varied significantly among reaches (upper, middle, and lower reaches) and between seasons (winter and summer), but their mcrA gene diversity showed no significant spatial or temporal variations. The copy numbers of Methanoperedens-like archaeal mcrA genes were 1.32 × 105–2.47 × 107 copies g−1 (dry weight), and the activity of nitrate-driven AOM was 0.25–1.73 nmol CH4 g−1 (dry weight) d−1, which could potentially reduce 10.3% of CH4 emissions from rivers. Significant spatio-temporal variations of mcrA gene abundance and nitrate-driven AOM activity were found. Both the gene abundance and activity increased significantly from upper to lower reaches in both seasons, and were significantly higher in sediment collected in summer than in winter. In addition, the variations of Methanoperedens-like archaeal communities and nitrate-driven AOM activity were largely impacted by the sediment temperature, NH4+ and organic carbon contents. Taken together, both time and space scales need to be considered for better evaluating the quantitative importance of nitrate-driven AOM in reducing CH4 emissions from riverine ecosystems.