Resilience of methane cycle and microbial functional genes to drought and flood in an alkaline wetland: A metagenomic analysis

Alkaline wetlands distributed in arid or semi-arid areas are hotspots of methane (CH4) emissions. Periods of drought and flood, although regular, are stressful events encountered by methanogenic anaerobes in alkaline wetlands. To investigate the response of the CH4 cycle of alkaline wetlands to such stresses, we take Zhalong wetland as an example, then determined the CH4 flux and soil microbiomes in the wetland during wet, dry, and flooded periods. The in-situ CH4 flux in the wet period was 9.55-17.29 mg.m(-2).h(-1), but sharply degraded to 3.37-6.61 mg.m(-2).h(-1) in the dry period. It resumed to 4.51-20.80 mg.m(-2).h(-1) when the wetland was flooded again, which indicated that methanogenesis is quite resilient to drought. Syntrophic acetogenesis, and subsequently aceticlastic methanogenesis, were the dominant methanogenic pathways and resisted drought. Members belonging to Syntrophobacterales were the dominant syntrophic acetogens. They enter a viable but non-culturable (VBNC) state to resist drought. The dominant Methanosarcinales have the ability to repair reactive oxygen species damage during dry periods. The community of CH4 sink was governed by anaerobic methanotrophs, which entered a VBNC state or used repair systems to survive dry periods. This study revealed the responses of the CH4 cycle and microbial functional genes to drought and flood in alkaline wetlands. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the response of the CH4 cycle in alkaline wetlands, using Zhalong wetland as an example. The research found that methanogenesis is quite resilient to drought, with syntrophic acetogenesis and aceticlastic methanogenesis as dominant pathways. The study also revealed the role of microbial functional genes in surviving drought and flood periods in alkaline wetlands.