Microbial diversity in lake–river ecotone of Poyang Lake, China

The ecological environment of lake–river ecotone is complex and changeable, it is an important water purification area and pollution buffer zone, where the microorganisms play an important role in the mediation of material cycle, nutrition transfer, and element transformation. Microbial diversity is sensitive to environmental changes. In this study, 12 water samples from the lake–river ecotone of the Poyang Lake in China were collected to determine microbial gene sequences employing next-generation DNA sequencing techniques, and to evaluate total nitrogen (TN) and total phosphorus (TP) using UV spectrophotometric method. The results showed the major Poyang Lake has the largest microbial population, followed by Yao Lake, Ganjiang River and Raohe River. Based on the Shannon and Simpson Index, major Poyang Lake has the largest biodiversity of microbial communities, followed by Ganjiang River, Yao Lake, and Raohe River. Microbial characteristics vary with the TN and TP concentration, for instance, the nitrifying bacteria were relatively rich in Yao Lake and Ganjiang River ecotone, and the polyphosphate-accumulating organisms (PAO) in Raohe River were richer than those in Ganjiang River. The tag numbers of Euryarchaeota, Acidobacteria, Chlamydiae and Proteobacteria in Ganjiang River were more than in Raohe River, while significant differences were found between the major Poyang Lake and other lake–river ecotone, the operational taxonomic units (OTU) number (removing singletons) of major Poyang Lake have 3047, which was far more than the others. The study indicates that the Poyang Lake serves as a huge microbial gene pool, including a large number of DNA from ammonia oxidizing bacteria to ammonia oxidizing archaea.