Results from carbon-14 studies of biochemical classes of dissolved organic carbon (DOC) and particulate organic carbon (POC) have shown that carbohydrate and protein derive from carbon dioxide that has been recently fixed into organic matter (i.e., modern in age), whereas the lipid fraction is the most highly aged (~103-104 yrs BP) component of both DOC and POC. The older age of the lipid fraction is believed to be due to differences in organic matter sources, residence times, and/or reactivity. However, more studies are needed to understand the age of the lipid fraction and its contribution to the average age of oceanic DOC and POC. For this reason, a scientist from the College of William and Mary Virginia Institute of Marine Science and her collaborator from Ohio State University plan to examine the sources (i.e., terrigenous, marine, natural, anthropogenic), transformations, and fate of lipophilic organic matter across the land-ocean boundary of Delaware Bay and its adjacent coastal waters. To attain their goal, the researcher will carry out a geochemical evaluation of the conservative vs. non-conservative behavior of different organic constituents (i.e., bulk DOC and POC and their lipid components) and their isotopic (delta14C and del13C) signatures as a function of salinity. This will provide information on the overall mean inputs and sinks of each constituent on the scale of the entire estuary. In addition, the photochemical and microbial reactivity of DOC, POC and lipid components will be evaluated in controlled incubation experiments on timescales relevant to estuarine mixing and residence times. It is anticipated that this study will provide new insights on how the lipophilic organic matter contributes to the age, reactivity, and cycling of DOC and POC in estuarine and coastal waters.
In terms of the broader impacts, at no cost to the project, the scientist from the College of William and Mary Virginia Institute of Marine Science plans to involve graduate students from the Universidade do Estado do Rio de Janeiro in the research project, thereby building a collaboration between U.S. and Brazilian scientists. One graduate student from the College of William and Mary Virginia Institute of Marine Science and one graduate student from Ohio State University would be supported and trained as part of this project.
