Assistant Professor Brandon M. Stephens

Institute of Oceanography, Nation Taiwan University

Abstract :
Heterotrophic bacterioplankton use oxygen and dissolved organic matter (DOM) to acquire energy, carbon and nutrients necessary for growth; however, the impacts of the chemical composition of DOM on the ratio of oxygen uptake to carbon respiration (i.e., respiratory quotient, RQ) and bacterioplankton growth efficiencies (BGEs) are not well constrained, particularly for nutrient-limited regions such as open oceans. To investigate the influence of DOM composition on RQ and BGEs we performed DOM remineralization bioassays over a senescing phytoplankton bloom in the eastern North Atlantic Ocean. We found that RQs averaged 1.39 ± 0.14 and that more oxidized DOM and nitrogen-containing compounds were utilized at elevated RQs and lower BGEs, which we hypothesized to be due to shifts in the energy yield per carbon atom. Results also suggest that bacterioplankton and archaea could be using oxygen in excess of predicted RQs via a combination of nitrification and partial oxidation reactions, with implications for future field studies seeking to derive RQs for bacterioplankton use of DOM.

Contact : Cheng-Shiuan Lee