Interactive effects of nutrients, oxygen, and composition on estuarine DOM biodegradation

Biodegradation of dissolved organic matter (DOM) fuels aquatic biogeochemistry and is controlled by interacting environmental and chemical factors. We investigated how nutrients, oxygen, and DOM composition alter rates of biodegradation in the Chesapeake Bay, USA, an estuary impacted by nutrient pollution and hypoxia that receives considerable terrestrial and freshwater DOM. Building on previous work, we predicted that nutrient and dissolved organic carbon (DOC) additions would stimulate biodegradation under aerobic and anaerobic conditions, and DOM composition would strongly influence rates of biodegradation and humification. 4-day respirometry experiments using Chesapeake Bay water were conducted to monitor changes in DOC concentration, carbon dioxide (CO₂) production, and DOM composition measured by optical properties. While nutrient additions did not alter total CO₂ accumulation, nitrogen and phosphorus additions reduced the time to peak CO₂ accumulation rates by ~2 hours, and algal-derived DOM led to ~50% more CO₂ accumulation than soil-derived DOM. Total CO₂ accumulation was approximately 10% higher under aerobic than anaerobic conditions. This suggests DOM biodegradation can be supported by alternative electron acceptors supplied by nutrient additions. These results demonstrate that interactions between controlling factors may lead to unanticipated changes in DOM biodegradation under shifting environmental conditions.

Presentation Preference: Poster

Primary Presenter: Lily Karg, Michigan Technological University (lilynoelkarg@gmail.com)

Authors:

Lily Karg, Michigan Technological University  (lnkarg@mtu.edu)

Amy Marcarelli, Michigan Technological University  (ammarcar@mtu.edu)

Steve Techtmann, Ohio State University  (techtmann.2@osu.edu)

Juliana D’Andrilli, University of North Texas  (Juliana.D'andrilli@unt.edu)