LEGACY EFFECTS OF PLANT COMMUNITY STRUCTURE ARE MANIFESTED IN MICROBIAL BIOFILM DEVELOPMENT WITH CONSEQUENCES FOR ECOSYSTEM CO2 FLUXES

In this study, we evaluated how shifts in the vegetation community associated with long-term changes in water-table position influence aquatic biofilm development and carbon dioxide (CO₂) flux. We quantified seasonal variation in biofilm composition and CO₂ fluxes in response to lowered and raised water-table position (relative to a control) during years with varying levels of background dissolved organic carbon (DOC). We then used nutrient diffusing substrates to evaluate cause-effect relationships between changes in plant subsidies and biofilm composition among water-table treatments. We found that background concentration of DOC determined whether plant subsidies promoted net autotrophy or heterotrophy which had consequences for net CO₂ flux. In conditions where background DOC was ≤ 40 mg L^-1, plant subsidies promoted autotrophic biofilm development. When background DOC concentration was ≥ 50 mg L^-1, plant subsidies promoted heterotrophic biofilm development. Conditions that favored autotrophic biofilm development resulted in net CO₂ uptake among all water-table treatments, whereas the site was a net source of CO₂ to the atmosphere in conditions that supported greater heterotrophy. Our finding suggest that drainage history interacts with changes in dominant plant functional groups to alter biofilm composition, which has significant consequences for ecosystem CO₂ fluxes.

Primary Presenter: Allison Rober, Ball State University (arrober@bsu.edu)

Authors:

Allison Rober, Ball State University  (arrober@bsu.edu)

Catherine Dieleman, University of Guelph  (cdielema@uoguelph.ca)

Evan Kane, Michigan Technological University  (eskane@mtu.edu)

Merritt Turetsky, University of Colorado Boulder  (merritt.turetsky@colorado.edu)

Kevin Wyatt, Ball State University  (khwyatt@bsu.edu)