Sediment nitrate dissimilatory reduction processes in the river-lake ecotone of Poyang Lake, China: Mechanisms and environmental implications

• Published in: Journal of soils and sediments Vol. 24; no. 10; pp. 3515 - 3529
• Main Authors: Jiang, Yinghui, Xie, Zhenglei, Ding, Mingjun, Zhang, Hua, Huang, Gaoxiang, Cao, Yun, Yin, Guoyu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2024; Springer Nature B.V
• Subjects: Abundance; Ammonium; Ammonium compounds; Aquatic ecosystems; Correlation analysis; Denitrification; Earth and Environmental Science; Ecosystems; Ecotones; Environment; Environmental impact; Environmental Physics; Eutrophication; Genes; Habitat selection; Lakes; Nitrate reduction; Nitrates; Nitrogen isotopes; Nitrous oxide; Nucleotide sequence; PCR; Polymerase chain reaction; Redundancy; Rivers; rRNA 16S; Sec 2 • Physical and Biogeochemical Processes • Research Article; Sediment; Sediment samplers; Sediment samples; Sediments; Soil Science & Conservation; Sulphides; Total organic carbon; China; Poyang Lake; Dissimilatory nitrate reduction; Sediment; N; Poyang Lake; O
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-024-03890-y

Purpose The river-lake ecotone in lake ecosystems can strongly influence sediment nitrate dissimilatory reduction processes. However, the mechanisms underlying these processes in river-lake ecotone ecosystems are still poorly understood. This study aims to investigate the rates of sediment nitrate dissimilatory reduction processes in Poyang Lake and clarify the mechanisms and environmental implications of these processes. Materials and methods Sediment samples from five river-lake ecotones and lake ecosystems were collected from Poyang Lake, China. Sediment nitrate reduction and N 2 O production rates were measured using 15 N isotope tracing experiments. The abundance of denitrifiers, anammox 16S rRNA bacteria, and nrfA genes was quantified using the polymerase chain reaction method. Correlation analysis, redundancy analysis, and stepwise linear regression were used to evaluate the mechanisms of sediment nitrate reduction processes. Results and discussion Sediments in the river-lake ecotone showed significantly higher denitrification (DEN), N 2 O production, dissimilatory nitrate reduction to ammonium (DNRA), and anammox rates compared to lake ecosystems. DEN was the dominant process contributing to nitrate reduction, accounting for 73.36% and 74.13% in the river-lake ecotone and lake ecosystem, respectively. DEN, N 2 O, and DNRA rates were significantly positively correlated with TOC, sulfide, and Fe 2+ contents, which control the abundance of denitrifying and nrfA genes, ultimately increasing these rates. Conclusion The annual input of reactive N to the lake from the watershed is almost equivalent to the annual N removal. However, higher DNRA and N 2 O production rates indicate that approximately 23.59% of the annual N input to the lake may be transformed to NH 4 + or N 2 O. N retention and N 2 O production in the river-lake ecotone significantly exceed those in the lake ecosystem, highlighting the ecotone as a hotspot for eutrophication risk and N 2 O emissions.