Inland waters are the important sources of the greenhouse gas methane (CH4). The production of CH4 is influenced by various factors, including the concentration of dissolved organic matter (DOM), redox conditions, and the composition of microbial communities, which exhibits obviously spatiotemporal heterogeneity in inland waters. Refractory DOM (RDOM) can resist rapid biodegradation and preserve up to thousands of years; therefore, it is important for assessing the natural carbon sequestration potential of aquatic ecosystems. As a critical part of carbon biogeochemical processes in inland waters, the production of CH4 and RDOM depends on the microbial successive processing of organic carbon. However, it is unclear yet the link of these two processes and the underlying microbial regulation mechanisms.
Prof. Baoli Wang's group conducted a large-scale environmental gradient survey across China's inland waters (Figure 1), with the measurement of CH4 concentration, DOM chemical composition, microbial community composition, carbon-cycling functional genes and related environmental parameters mainly by chromatographic, optical, mass spectrometric, and high-throughput sequencing analyses. This study preliminarily explored the microbial-driven mechanisms on carbon turnover in inland waters, highlighted the role of microbial keystone taxa, and will provide some references for the future laboratory experiments (e.g., the selection of microbial species).
Figure 1. Sampling sites, CH4 concentration and DOM composition characteristics in China’s inland waters
Figure 2. Keystone taxa drive the synchronous production of methane and refractory dissolved organic matter
This study found that CH4 and RDOM had a similar spatial distribution pattern in China's inland waters (Figure 1). In the studied inland waters (including lakes, rivers, wetlands, and reservoirs), keystone taxa (i.e., Fluviicola and Polynucleobacter) were universally present and drove the synchronous production of CH4 and RDOM. Keystone taxa played an important role in enhancing microbial cooperation, which could promote the transformation of labile DOM into RDOM and meanwhile benefit methanogenic microbial communities to produce CH4. This process was also influenced by environmental factors such as total nitrogen and dissolved oxygen concentrations (Figure 2). Future studies need to combine more field investigations and laboratory control experiments to fully understand these complex processes.
Considering that CH4 emission and RDOM production are closely related to the carbon source-sink relationship, this study will help to accurately evaluate the carbon budget in inland aquatic ecosystems. This study has been published in Water Research. PhD. Xinjie Shi is the first author, Prof. Baoli Wang and Dr. Wanzhu Li are the corresponding authors. This work was supported by the National Natural Science Foundation of China (42293264 and 42293262) and the Postdoctoral Fellowship Program of CPSF (GZC20241196).
Paper Information: Xinjie Shi, Wanzhu Li*, Baoli Wang*, Na Liu, Xia Liang, Meiling Yang, Cong-Qiang Liu. 2024. Keystone taxa drive the synchronous production of methane and refractory dissolved organic matter in inland waters. Water Research. https://doi.org/10.1016/j.watres.2024.122821
