Abstract
I developed a method to quantify environmental adenylate concentrations and production rates, using an optimized high pressure liquid chromatography (HPLC) protocol with brief radiolabled phosphate (32P) incubations.This high-throughput method greatly improved previously developed approaches, which only quantified ATP concentrations or were too laborious for extensive application. I completed the first comprehensive transect survey quantifying particulate ATP. I sampled along 32.5° S in the Pacific Ocean, from the subtropical gyre to the upwelling waters near Chile, with the Global Ocean Ship-based Hydrographic Investigations Program. I observed significantly greater concentrations of ATP per measured biomass below the deep chlorophyll maximum than in the euphotic zone, indicative of changes in microbial energy storage. I hypothesized this greater biomass normalized ATP was due to lower availability of external energy sources and greater abundances of chemoautotrophs in subeuphotic waters; future studies are needed to fully assess these hypotheses. Our findings suggested that stored energy, in the form of ATP, was more important for deeper microbes and can provide more nuanced insights into the microbial system in natural seawater than previously thought. I applied the adenylate HPLC and radioisotope methods to measure responses of the natural coastal microbial communities to changing environmental conditions in Biscayne Bay, Florida. I conducted an array of multiday incubations assessing the impact of temperature on the growth and metabolic rates of the microbial community. Microbial communities under increased temperature conditions exhibited faster dissolved phosphate turnover and quicker metabolic turnover rates compared to those held at ambient seawater temperatures. However, I did not observe any significant differences in growth rates between the two conditions. The work completed in this dissertation demonstrates the application of a new technique for understanding the metabolic activity of microbes and flow of energy and phosphorus in the ocean.