Legacy Effects of Plant Community Structure Are Manifested in Microbial Biofilm Development With Consequences for...

Area of Science:

• Environmental Science
• Ecology
• Biogeochemistry

Background:

• Northern aquatic ecosystems are sensitive to hydrological changes.
• Understanding carbon flux requires knowledge of plant-ecosystem interactions.
• Biofilm communities play a critical role in aquatic carbon cycling.

Purpose of the Study:

• To investigate the relationship between hydrology, plant communities, and carbon dioxide (CO2) exchange in an Alaskan fen.
• To determine how altered water tables and dissolved organic carbon (DOC) levels affect biofilm composition and function.
• To establish cause-effect relationships between plant subsidies and biofilm responses.

Main Methods:

• Quantified seasonal biofilm composition and CO2 exchange under varied water table positions.
• Utilized nutrient-diffusing substrates (NDS) to assess plant leachate impacts.
• Analyzed data in relation to background DOC concentrations.

Main Results:

• Background DOC concentration dictated whether plant subsidies promoted autotrophic or heterotrophic biofilms.
• Low DOC (≤40 mg L⁻¹) favored autotrophic biofilms; high DOC (≥50 mg L⁻¹) favored heterotrophic biofilms.
• Autotrophic conditions led to net CO2 uptake, while heterotrophic conditions resulted in net CO2 release.

Conclusions:

• Hydrology and plant functional groups interact to shape biofilm communities.
• Biofilm composition significantly impacts ecosystem-level CO2 exchange in fens.
• DOC levels are a critical factor mediating the effects of hydrology on carbon cycling.