Interactions Between Reactive Nitrogen and Manganese: Implications for Marine Nitrous Oxide Cycling

Amanda R. Cavazos
Friday, March 6, 2020 - 1:00pm
ES&T, Rm. L1205
Dr. Jennifer Glass (Advisor), Dr. Joel Kostka , Dr. Martial Taillefert, Dr. Yuanzhi Tang, and Dr. Jay Brandes (SkiO, UGA)

Nitrous oxide (N2O) is a potent greenhouse gas that can destroy stratospheric ozone. In marine environments, N2O is assumed to be produced and consumed solely by nitrogen-metabolizing microbes. It has been shown, however, that intermediate metabolites from these microbes can potentially leak out of cells and react with metal oxides to produce N2O. Recent studies have shown that the nitrification intermediate hydroxylamine (NH2OH) can chemically react with manganese (Mn) oxides in soils to yield N2O. Little is known about these interactions in marine systems. This dissertation aims to constrain the importance of coupled biotic/abiotic interactions between reactive nitrogenous intermediates and manganese oxides in marine systems by (1) characterizing the kinetics of NH2OH oxidation by an environmentally-relevant Mn oxide, (2) developing a rapid, readily-available, and cost-effective method to visualize associations of microbes and manganese oxide particles, and (3) developing a method to more rapidly and accurately measure NH2OH in water samples. My findings suggest that NH2OH chemo-oxidation is environmentally relevant in marine systems. The methods developed in this dissertation can be used to further build our understanding of N-Mn coupled biogeochemistry in marine systems. Future studies can accurately and rapidly measure marine NH2OH and other reactive intermediates to better constrain the biogeochemical role of coupled biotic-abiotic and N-Mn interactions.