Environmental and Microbial Interactions Shape Methane-Oxidizing Bacterial Communities in a Stratified Lake

Area of Science:

• Environmental microbiology
• Aquatic microbial ecology
• Biogeochemistry

Background:

• Stratified lakes harbor methane-oxidizing bacteria (MOB) crucial for mitigating atmospheric methane release.
• Understanding MOB community dynamics and their environmental drivers is essential for predicting methane fluxes.
• Previous research has not fully explored the spatio-temporal dynamics of MOB and their interactions within the water column.

Purpose of the Study:

• To investigate the spatio-temporal dynamics of MOB and total bacterial communities in a stratified lake.
• To identify key physico-chemical parameters and microbial interactions structuring MOB communities.
• To assess the influence of the broader bacterial community on MOB composition.

Main Methods:

• Sampling of four highly resolved vertical profiles across three years in a shallow, sub-alpine lake.
• Analysis of MOB and bacterial community composition using molecular techniques.
• Measurement of a comprehensive set of physico-chemical parameters (e.g., methane, oxygen, pH, nutrients, metals).
• Application of network analysis and partial redundancy analysis to explore community assembly drivers.

Main Results:

• Non-randomly assembled MOB communities were consistently detected across all lake compartments.
• Methane and oxygen gradients, pH, light, copper, iron, and dissolved nitrogen significantly influenced MOB structure.
• A bacterial-environmental network explained up to 84% of MOB abundances.
• Spatio-temporal MOB community shifts were congruent with total bacterial community changes (51%).
• Bacterial community composition exclusively explained 22% of MOB abundance variance.

Conclusions:

• MOB communities in stratified lakes are structured by both environmental gradients and microbial interactions.
• Microbial interactions are significant drivers of MOB community assembly along the lake's depth gradient.
• This study highlights the complex interplay of factors governing methane cycling in aquatic ecosystems.