| Abstrakt: |
Purpose: The aim of this work was to determine the contributions of denitrification and anammox to nitrogen loss in the sediments of the Yellow River wetland and to explore the abundance of functional genes involved in these two processes. Methods: Three samples were collected from areas with different vegetation covers: a P. australis-covered site (LW), a T. orientalis-covered site (XP), and a site without vegetation coverage (GT). The potential anammox and denitrification rates were estimated using nitrogen isotope tracer technology by quantifying 29N2 and 30N2 produced in a strictly anaerobic incubation of sediment with labeled 15NO3− as the reactive substrate. According to the production rates of 29N2 and 30N2, denitrification and anammox rates were simultaneously measured. Metagenomic sequencing was used to analyze the abundances of functional microbes and functional genes. Results: The total nitrogen removal rates (denitrification + anammox) in the vegetation-covered sites were three to six times that in the GT (GT: 0.28 mg N kg−1 d−1; LW: 1.73 mg N kg−1 d−1; XP: 0.94 mg N kg−1 d−1). The denitrification rates at the LW, XP, and GT were 1.50 mg N kg−1 d−1, 0.80 mg N kg−1 d−1, and 0.07 mg N kg−1 d−1, respectively. The anammox rates at the GT, LW, and XP were 0.21 mg N kg−1 d−1, 0.23 mg N kg−1 d−1, and 0.14 mg N kg−1 d−1, respectively. The denitrification rates were six times higher than the anammox rates in the vegetation-covered sites and thus represented the dominant nitrogen removal pathway, accounting for 85% (LW) and 86% (XP) of nitrogen loss. However, anammox was the dominant process of N2 production at the GT. Metagenomic analysis showed that the GT did not meet the lower limit of gene abundance detection. The anammox gene was not detected, and the abundance of the denitrification gene was high, which was consistent with the denitrification rate. In addition, the continuous accumulation of 15NH4+ and the abundance of functional genes indicated the existence of the DNRA process in the Yellow River wetland. Conclusion: Denitrification is the main nitrogen removal pathway in Yellow River wetland sediment, and vegetation coverage accelerates the nitrogen removal rate. Moreover, the DNRA process is of great significance for the efficient utilization of nitrogen in the Yellow River wetland. [ABSTRACT FROM AUTHOR] |
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