Depth induced assembly discrepancy of multitrophic microbial communities affect microbial nitrogen transformation...

Area of Science:

• Environmental Microbiology
• River Ecology
• Biogeochemistry

Background:

• River ecological functions depend on microbial community structures and functions.
• Understanding microbial variations within river cross-sections is crucial for accurate metabolic processing predictions.
• Previous studies lacked comprehensive analysis of microbial community dynamics across river depths.

Purpose of the Study:

• To investigate the distributions, co-occurrence networks, and assemblies of bacterial and microeukaryotic communities in river cross-sections.
• To determine the feedback of these microbial communities on nitrogen transformation.
• To identify the primary drivers of microbial community structure and function across varying depths.

Main Methods:

• Coupling ecological theory, biogeochemistry, and DNA meta-barcoding.
• Analysis of microbial community composition and co-occurrence networks.
• Quantification of microbial assembly processes using the β-nearest taxon index.
• Structural equation modeling to assess environmental drivers of nitrogen distribution.

Main Results:

• Cross-sectional depth was the primary factor regulating sediment bacterial and microeukaryotic communities.
• Microbial co-occurrence networks became simplified and less stable with increasing depth.
• The H2 layer (10-20 m) showed the highest variation in microbial selection processes and nitrogen removal potential.
• Sediment nitrogen distribution was depth-dependent, with the H2 layer primarily influenced by bacterial communities and particle size distribution.

Conclusions:

• Cross-sectional depth is a critical determinant of microbial community structure and nitrogen cycling in rivers.
• The H2 sediment layer plays a key role in microbial nitrogen removal, driven by specific environmental pathways.
• Findings enhance understanding for improved river management and ecological restoration strategies.