My training and research interests lie in the areas of marine organic geochemistry and chemical oceanography. I use chemical "signatures" present in environmental samples to obtain information about the sources of organic matter important to freshwater, estuarine and marine ecosystems. This information can be present in elemental ratios, the presence of specific organic compounds, and the natural and radiocarbon isotopic ratios of biologically-important elements (C, N, S) and organic compounds. Collectively, these geochemical tools are termed "biomarkers". Important characteristics of biomarkers are: (1) their source specificity and (2) the stability of the compounds. Data obtained through these studies can provide insights into the sources and reactivity of organic materials produced within complex marine and freshwater ecosystems. This information can tell us, for example, whether production is primarily supported by phytoplankton, terrigenous or marsh vascular plants, submerged aquatic vegetation (e.g., seagrass), or inputs from the rivers draining into the estuary.