Abstract
Dissolved organic matter (DOM) exists as various forms within seawater, which as a result may affect the surrounding
microbial communities. To understand how varying DOM substrates affect microbial assemblages, coastal seawater was amended with glucose, leucine, Macrocystis pyrifera exudate, or Thalassiosira weissflogii lysate. Key responses such as bacterial growth efficiency, oxygen utilization rates, Total Organic Carbon drawdown rates, and microbial community structures were analyzed over the period of one week for each treatment. We hypothesized that the glucose and leucine treatments would have the highest bacterial growth efficiency, highest oxygen utilization rates, and greatest change in bacterial carbon. The results indicated that due to nitrification leucine and T. weissflogii lysate treatments experienced highest oxygen utilization rates, while T. weissflogii lysate and M. pyrifera exudate treatments had similar Total Organic Carbon drawdown rates and bacterial abundance due to their heterogenous DOM nature. Microbial community structures varied over time, but at each time point remained similar comparing treatments. The experiment’s findings indicate that a variation of DOM substrates may affect microbial assemblages, and that these effects vary based on the analyzed measurement.
microbial communities. To understand how varying DOM substrates affect microbial assemblages, coastal seawater was amended with glucose, leucine, Macrocystis pyrifera exudate, or Thalassiosira weissflogii lysate. Key responses such as bacterial growth efficiency, oxygen utilization rates, Total Organic Carbon drawdown rates, and microbial community structures were analyzed over the period of one week for each treatment. We hypothesized that the glucose and leucine treatments would have the highest bacterial growth efficiency, highest oxygen utilization rates, and greatest change in bacterial carbon. The results indicated that due to nitrification leucine and T. weissflogii lysate treatments experienced highest oxygen utilization rates, while T. weissflogii lysate and M. pyrifera exudate treatments had similar Total Organic Carbon drawdown rates and bacterial abundance due to their heterogenous DOM nature. Microbial community structures varied over time, but at each time point remained similar comparing treatments. The experiment’s findings indicate that a variation of DOM substrates may affect microbial assemblages, and that these effects vary based on the analyzed measurement.
This project was completed in support of graduate student Rachel Sandquist and in submission of my final paper for my Microbiology Laboratory class. The assignment was to create a report formatted in the style of a peer-reviewed research journal. Each group of students were in charge of a certain DOM substrate for this experiment. I learned how to measure bacterial abundance and sample for microbial community compositions. Utilizing RStudio, I analyzed and visualized the data.
