Aerobic methane oxidation under distinct shrinkage scenario of Lake Ganggeng in Inner Mongolia Autonomous Region

Abstract:

[Objective] To elucidate the variation patterns of aerobic methanotrophy under the shrinkage process from sediment to saline land and grassland. [Methods] Lake sediment, saline and grassland soils were collected from the shrinkage gradient of Lake Ganggeng in Inner Mongolia, and incubated under different initial CH₄ concentrations to determine their CH₄ oxidation potentials. We analyzed methanotrophic community composition and their abundance change by real-time quantitative PCR and high-throughput sequencing techniques. [Results] During lake shrinkage, soil properties of lake sediment and saline soil showed similar variation trends with methane oxidation rates, and were significantly different from that of grassland soil. In response to shrinkage, the relative abundance of Methylococcus increased significantly (with the relative abundance of 19.2%, 48.8% and 78.3% in lake sediment, saline and grassland soils, respectively), whereas Crenothrix decreased from 54.7% to 32.1% and 13.9%. Microcosm incubation of these samples under different initial CH₄ concentrations demonstrated the predominant increase of Crenothrix and Methylococcus in lake sediment; While Methylococcus and Methylomonas dominated the increase in saline soil; Crenothrix increased 7.81% in grassland soils (196 folds). [Conclusion] Lake shrinkage significantly decreased methane oxidation potential, and methanotrophic community also changed, with numerically dominant Methylococcus and Crenothrix in sediment and grassland respectively. However, it is noteworthy that under high CH₄ concentration, Crenothrix increased rapidly, most likely playing important roles during methane oxidation in all samples tested.

Key words:lake shrinkage;ecological succession;CH₄;methanotroph;pmoA gene