Spatial patterns of total and methane-cycling microbial communities in surface sediments of the eastern Guangdong...

Methane, the second most prevalent greenhouse gas, is vital to climate change. Previous studies have revealed that coastal areas are hotspots for methane cycling. As methane production and oxidation are mainly mediated by microorganisms, the investigation of methane-cycling microbial community characteristics can deepen our understanding of methane metabolic processes and the underlying mechanisms. In this study, amplicon sequencing was employed to demonstrate the spatial patterns of total microbial, methanogenic, and methanotrophic communities in surface sediments of the eastern Guangdong coast in summer and to identify significant environmental factors affecting the communities. The results revealed that the total and methane-cycling microbial communities exhibited spatial heterogeneity, with both diversity and composition shifting at different distances from the shore. Family Methanosarcinaceae especially methylotrophic Methanococcoides dominated the methanogenic community, with the relative abundance of 27.57 % in the coastal stations (distance from the shore 5-20 km) and increased to 69.13-72.62 % in the nearshore and offshore stations. Type II methanotroph Methylocystis accounted for 48.71 % of methanotrophic community on the coast, whereas unclassified Bacteria dominated with the relative abundance of more than 70 % in the nearshore and offshore environments. The distance from the shore, organic matter, and hydrodynamic processes are crucial for microbial communities. The distance from the shore represents the intensity of anthropogenic activities, and hydrodynamic processes contribute to the differentiation of total microbial community structure between the western and eastern nearshore stations. These findings could provide further insight into microbial methane metabolism in coastal environments.