Hydrogenotrophic pathway dominates methanogenesis along the river-estuary continuum of the Yangtze River

Biao Li; Hongwei Wang; Anxing Lai; Jingya Xue; Qiong Wu; Chunyan Yu; Ke Xie; Zhendu Mao; Huabing Li; Peng Xing; Qinglong L Wu

doi:10.1016/j.watres.2023.120096

Hydrogenotrophic pathway dominates methanogenesis along the river-estuary continuum of the Yangtze River

Water Res. 2023 Jul 15:240:120096. doi: 10.1016/j.watres.2023.120096. Epub 2023 May 20.

Authors

Biao Li¹, Hongwei Wang², Anxing Lai², Jingya Xue³, Qiong Wu⁴, Chunyan Yu⁴, Ke Xie², Zhendu Mao², Huabing Li⁵, Peng Xing⁶, Qinglong L Wu⁷

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
² State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100039, China.
³ School of Geographical Sciences, Nanjing Normal University, Nanjing 210023, China.
⁴ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; College of Life Sciences, Hebei University, Baoding 071002, China.
⁵ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
⁶ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: pxing@niglas.ac.cn.
⁷ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China; Sino-Danish Center for Education and Research, University of Chinese Academy of Sciences, Beijing 100039, China. Electronic address: qlwu@niglas.ac.cn.

PMID: 37229838
DOI: 10.1016/j.watres.2023.120096

Abstract

Rivers are considered as an important source of methane (CH₄) to the atmosphere, but our understanding for the methanogenic pathway in rivers and its linkage with CH₄ emission is very limited. Here, we investigated the diffusive flux of CH₄ and its stable carbon isotope signature (δ¹³C-CH₄) along the river-estuary continuum of the Yangtze River. The diffusive CH₄ flux was estimated to 27.9 ± 11.4 μmol/m²/d and 36.5 ± 24.4 μmol/m²/d in wet season and dry season, respectively. The δ¹³C-CH₄ values were generally lower than -60‰, with the fractionation factor (α_c) higher than 1.055 and the isotope separation factor (ε_c) ranged from 55 to 100. In situ microbial composition showed that hydrogenotrophic methanogens accounts for over 70% of the total reads. Moreover, the incubation test showed that the headspace CH₄ concentration by adding CO₂/H₂ to the sediment was orders of magnitude higher than that by adding trimethylamine and sodium acetate. These results jointly verified the river-estuary continuum is a minor CH₄ source and dominated by hydrogenotrophic pathway. Based on the methanogenic pathway here and previous reported data in the same region, the historical variation of diffusive CH₄ flux was calculated and results showed that CH₄ emission has reduced 82.5% since the construction of Three Gorges Dam (TGD). Our study verified the dominant methanogenic pathway in river ecosystems and clarified the effect and mechanism of dam construction on riverine CH₄ emission.

Keywords: Diffusive flux; Methanogenic pathway; Microbial community; River-estuary continuum; Stable carbon isotope.

MeSH terms

Carbon
Carbon Isotopes / analysis
Ecosystem
Estuaries*
Methane / metabolism
Rivers*

Substances

Carbon Isotopes
Carbon
Methane