Ph.D Defense Seminar


Seth Thompson
Doctoral Candidate, Water Resources Science

June 6, 2019


Degradation and Production of Dissolved Organic Matter by Heterotrophic Bacteria

Aquatic ecosystems transport large amounts of organic matter from the landscape to the oceans. Along this pathway, heterotrophic bacteria rapidly cycle these compounds by acting as both degraders and producers of organic compounds. Understanding the ultimate fate of the organic matter and predicting how increased organic matter exports from terrestrial ecosystems will impact its delivery to the ocean, requires a better understanding of the factors that influence organic matter degradation and production in freshwater systems. While many scientists have approached this problem by focusing on microbial modifications of carbon (C), much less attention has been paid to other major elements found in organic molecules (namely nitrogen (N) and phosphorus (P)). A more integrated approach that incorporates microbial processing of both C and major macronutrients such as N and P is needed to describe the biogeochemical transformations of organic matter in freshwaters. Here I present work from my dissertation examining the degradation and production of dissolved organic matter by heterotrophic bacteria, specifically focusing on dissolved organic phosphorus (DOP). I quantified the degradation rates and overall bioavailability of DOP across 27 unique aquatic systems and explore important environmental and chemical regulators of these rates. Additionally I explore the production of organic matter by heterotrophic bacteria using laboratory cultures. I end with a transition away from research on aquatic ecology into what I consider to be another fundamental aspect of being a scientist: training the next generation of scientific thinkers.