Research Seminar: Alexandria Hounshell, IMS; UNC-CH

“Using fluorescence to determine dissolved and particulate organic matter dynamics in aquatic systems.” Rapid urban, agricultural, and industrial expansion in coastal plain watersheds has led to increased nutrient loading and over-enrichment (i.e., eutrophication) in freshwater and estuarine ecosystems worldwide. Harmful effects include fish kills, hypoxia/anoxia, and harmful algal blooms which disrupt both the resources (drinking water, fisheries, recreation, tourism) and sustainability of impacted systems. Historically, research and management strategies have focused on controlling inorganic nutrient loading (as nitrogen [N] and phosphorous). In recent years, the role of organic matter (OM) as a N source for primary production and microbial metabolism in N-limited waters, has been recognized. Evidence suggests anthropogenic OM and organic N (ON) constituents, from urban runoff, agriculture, industrial, and wastewater treatment effluent will promote algal and bacterial growth. The development of optical techniques (excitation emission matrices coupled with parallel factor analysis, EEM-PARAFAC) to identify and track both dissolved and particulate OM fluorescent signatures through aquatic ecosystems has allowed for rapid and detailed information on OM dynamics in these systems. Using both field monitoring studies and nutrient addition bioassays coupled with the EEM-PARAFAC technique, I will explore the bio-reactivity and fate of identified ON sources to coastal plain ecosystems. The proposed studies will seek to delineate the biological and chemical pathways of ON in aquatic systems and demonstrate the importance of ON to phytoplankton and bacterial community dynamics and the ultimate ecological health of freshwater and estuarine ecosystems.