Dry-season precipitation reshapes functional gene composition and modulates ecosystem functioning in the tropical...

Area of Science:

• Freshwater microbial ecology
• Biogeochemical cycling
• Ecosystem resilience

Background:

• Pulsed hydrological disturbances like alternating drought and precipitation reshape freshwater ecosystems.
• Microbial communities drive carbon (C), nitrogen (N), and phosphorus (P) cycling but their responses to disturbances are complex and poorly understood.

Purpose of the Study:

• To systematically compare microbial functional gene dynamics before and after precipitation events during the dry season in a tropical river.
• To elucidate the regulatory mechanisms of microbial functional responses to pulsed hydrological disturbances.

Main Methods:

• Comparative analysis of microbial functional gene composition and diversity (Shannon diversity, spatial similarity).
• Analysis of C, N, and P cycling pathways and their metabolic shifts.
• Co-occurrence network analysis to identify changes in microbial interactions and keystone taxa.
• Partial least squares path modeling (PLS-PM) to assess regulatory effects of environmental factors and diversity on microbial functions.

Main Results:

• Precipitation significantly reduced microbial diversity and spatial similarity of C and N cycling genes, altering overall functional gene composition.
• Carbon metabolism shifted towards heterotrophic pathways; phosphorus metabolism favored energy-efficient organic-phosphorus hydrolysis.
• Nitrogen cycling showed stage-specific responses, with increased denitrification but inhibited terminal reduction steps.
• Microbial co-occurrence networks showed fewer positive associations and a shift in keystone taxa.
• Precipitation amplified direct environmental regulation of microbial genes and reversed the effect of microbial diversity on P cycling.

Conclusions:

• Hydrological disturbances profoundly impact microbial community structure and function in freshwater ecosystems.
• Post-precipitation, C-N-P cycling relies on a few dominant taxa, highlighting potential vulnerabilities in ecosystem stability.
• Findings offer insights into freshwater ecosystem management and resilience assessment under climate change-induced hydrological alterations.