Collaborative Research: Formation of Modified Biochemicals and their Contribution to Dissolved Organic Nitrogen in Marine Ecosystems

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ABSTRACTOCE-9907069 & OCE-9908808Although dissolved organic nitrogen is known to be the largest reservoir of reduced nitrogen in the world ocean, little is known about its origin, reactivity, and long-term fate. Recent research indicates that high-molecular-weight dissolved organic nitrogen is dominated by compounds with amide linkages - like those found in biogenic protein molecules. The sources of these amides are unknown, but proteins and chitins (reaction products between amino acid and sugar monomers) are considered prime candidates. In this study, an organic geochemist at the University of Maryland Center for Environmental Studies and a microbial ecologist at the University of Delaware will combine talents to investigate the mechanisms by which this DON is formed. There are three major research questions: (1) Is protein or chitin modified to forms unrecognizable as amino acid or amino sugar-containing polymers?; (2) Does the physical matrix surrounding these compounds enhance or inhibit chemical/microbiological processes?; and (3) What is the contribution of these modified byproducts to the high molecular weight dissolved and particulate organic matter in the Delaware estuary and coastal ocean? A variety of state-of-the art techniques of organic analysis and microbial biochemistry will be employed to address these questions. The investigators anticipate that this study will significantly expand our understanding of the processes responsible for the presence and persistence of these nitrogenous substances in marine waters.