Cascade damming impacts on microbial mediated nitrogen cycling in rivers

Xun Wang; Peifang Wang; Chao Wang; Juan Chen; Bin Hu; Qiusheng Yuan; Chenggong Du; Xiaolei Xing

doi:10.1016/j.scitotenv.2023.166533

Cascade damming impacts on microbial mediated nitrogen cycling in rivers

Sci Total Environ. 2023 Dec 10:903:166533. doi: 10.1016/j.scitotenv.2023.166533. Epub 2023 Aug 23.

Authors

Xun Wang¹, Peifang Wang², Chao Wang¹, Juan Chen¹, Bin Hu¹, Qiusheng Yuan¹, Chenggong Du³, Xiaolei Xing¹

Affiliations

¹ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
² Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China. Electronic address: pfwang2005@hhu.edu.cn.
³ Jiangsu Key Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal University, Huai'an, Jiangsu 223300, China.

PMID: 37625716
DOI: 10.1016/j.scitotenv.2023.166533

Abstract

Rivers display essential role in nitrogen (N) cycling in terrestrial and aquatic ecosystems, but now they are suffering from damming worldwide, especially from cascade damming. Despite of the importance of microorganisms in biogeochemical nutrient cycling, little attention has been paid to microbial functional biogeography under damming disturbances. Here, the Geochip microarray was applied to investigate the microbial mediated N cycling across the single-dammed Yarlung Tsangpo-Brahmaputra River and the cascade-dammed Lancang-Mekong River in southwest China. Our results showed that the N cycling processes (nitrogen fixation, ammonification, denitrification, nitrification and anammox) were stimulated in reservoirs in both rivers and the enhancement was inversely coupled with hydraulic retention time, but the recovery of N-cycling gene abundance in downstream of dam was intervened by cascade damming. Moreover, N-cycling gene composition was significantly altered in the single-dammed river, while no remarkable change was found in the cascade-dammed reaches. However, different from the unvaried gene composition, cascade damming intervened the recovery of N-cycling gene flow connectivity and resulted in the continuous decrease of connectivity in cascade damming reaches. In addition, in the single-dammed river, nutrients were the important drivers for variation in gene abundance, while they did not influence gene composition. Meanwhile, the abundance and composition of N-cycling genes in the cascade-dammed river were both significantly correlated to geographical parameters and water physical characteristics. Therefore, our study has vital implications for anticipating microbial functional response and biogeochemical feedback to ongoing cascade damming, contributing to the protection of river ecosystems under river regulation.

Keywords: Gene abundance; Gene flow connectivity; Hydraulic retention time; Nitrogen-cycling gene; River damming.