Spatiotemporal heterogeneity of nitrogen transformation potentials in a freshwater estuarine system
Jiali Lü1, Shiqin Wang2, Binbin Liu2
1Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021, China; Sino-Danish College of University of Chinese Academy of Sciences, Beijing 101408, China; Sino-Danish Centre for Education and Research, Beijing 101408, China; Key Laboratory of Water Cycle & Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen 999017, Denmark.
Abstract:
Under the influence of water diversion, the microbial community composition of estuarine waters and sediments might have complex spatiotemporal variations. Microbial interactions with N are significant for lake water quality. Therefore, the largest lake receiving seasonal water diversion in the North China Plain was selected as the study area. Based on 16S rRNA high-throughput sequencing and metagenomic sequencing techniques, this study analysed temporal (June-December) and spatial (estuary-pelagic zone) changes in the microbial community and functional gene composition of water and sediment. The results showed that the water microbial community composition had temporality, while sediment microbes had spatiality. The main causes of temporality in the aquatic microbial community were temperature and nitrate-N concentration, while those of sediment were flow velocity and N content. Additionally, there were complex interactions between microbial communities and N. In water, temporal variation in the relative abundance of N-related functional genes might have indirectly contributed to inorganic N composition in June (nitrite-N > ammonia-N > nitrate-N) and August (nitrite-N > nitrate-N > ammonia-N). High nitrate-N concentrations in December influenced the microbial community composition. In sediment, the estuary had higher N functional genes than the pelagic estuary, creating a relatively active N cycle and reducing total N levels in the estuary. This study revealed a potentially overlooked N sink and a flow velocity threshold that has great impacts on microbial community composition. This research contributes to a deeper understanding of the estuarine N cycle under the influence of water diversions, with implications for the calculation of global N balances and the management of lake water environments.
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