Aerobic methane synthesis and dynamics in a river water environment

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• River Ecology

Background:

• Aerobic biogenic methane production is increasingly recognized as a significant process in natural environments.
• Understanding methane sources in rivers is crucial for accurate environmental assessments and climate modeling.
• Previous research has highlighted potential links between microbial activity, organic matter, and methane cycling.

Purpose of the Study:

• To investigate the phenomenon of aerobic biogenic methane production in a free-flowing river system.
• To determine the relationship between methane concentrations, environmental factors, phototrophic microorganisms, and methylated amines.
• To assess the metabolic potential of the river microbiome in methane synthesis.

Main Methods:

• Methane concentrations were monitored in the Yellowstone River, correlating with temperature, chlorophyll a (Chl a), and methylated amines.
• Diurnal measurements and surface flux assessments were conducted in different river zones (edge vs. open current).
• Laboratory experiments involved spiking river water with glycine betaine (GB) or methylamine (MMA) to evaluate methane production.

Main Results:

• Methane concentrations positively correlated with temperature and Chl a, peaking at night and lowest during peak sun.
• Higher methane efflux was observed in quiescent edge waters compared to the open flowing current.
• While methylated amines were present, their release during a microbial lytic event did not correlate with increased methane; however, spiking with GB or MMA significantly increased methane production.

Conclusions:

• Phototrophic microorganisms play a role in methane synthesis within riverine environments.
• The river's microbiome demonstrates a metabolic capability to convert methylated amines into methane.
• Riverine methane concentrations exhibit dynamic diurnal and seasonal variations.