Biogeographic Pattern of Methanogenic Community in Surface Water along the Yangtze River

Abstract

Methanogenesis from oxic water has been proven to be a significant component of methane source in large and deep freshwater ecosystems. However, the biogeography of methanogenic community in surface water of large rivers remains uncertain. Here, the community ecology and biogeographic pattern of methanogenic community along the Yangtze River (one of the largest rivers in the world) were studied by using high-throughput sequencing, and the relative importance of environmental and spatial variables on the assemblage of methanogenic community was assessed. The results showed a distinct spatial distribution that the Shannon diversity and Shannon evenness of methanogenic community in downstream of the Yangtze River were significantly higher than those in upstream and midstream sections. The most abundant three genera of methanogenic community were Methanobacterium, Methanosarcina and Methanosaeta, which did not exhibit significant difference between different sections. Besides, the composition of methanogenic community also showed a clear spatial variation along the river. Significant distance effects appeared on both methanogenic community and environmental variables. However, no significant relationship was found between methanogenic community and environmental variables. Compared to the limited contributions of spatial and environmental variables, interactions among taxa could be an important driver in structuring the assembly of methanogenic community. In addition, Methanobacteriales, Methanomassiliicoccales and Methanocellales were the key species of methanogenic community in upstream, midstream and downstream sections, respectively. Overall, the methanogenic community exhibited obvious biogeographic pattern along the Yangtze River, which was attributed to a joint effect of abiotic and biotic factors.