Microbial biomass in sediments affects greenhouse gas effluxes in Poyang Lake in China

Lake sediments accumulate large amounts of greenhouse gases (GHGs) through microbial decomposition of organic matter. To investigate the relationship between microbial biomass and GHG effluxes, we conducted a large-scale survey in Poyang Lake, the largest freshwater lake in China. We measured GHG effluxes using the floating chamber method at 42 sampling sites for three days and also measured microbial biomass using the phospholipid fatty acids (PLFAs) method. We found that the methane emission rate was positively and linearly related to total microbial biomass, anaerobic biomass, and anaerobic biomass excluding anaerobic methanotrophs. In addition, nitrous oxide efflux normalized to the amount of organic carbon in the sampling sediment (N2O/SOC) was significantly correlated with fungal biomass and the ratio of fungal biomass to total microbial biomass. But there were no significant relationships between the CO2 and CH4 normalized efflux in the sampling sediment and the biomasses of microbial groups. These results suggest that we could manage GHG emissions by considering the factors regulating microbial biomass in the lake sediments.