PhD Proposal Defense: Alexandria Hounshell

The Ph.D. Proposal Defense of Alexandria Hounshell will be presented before the UNC Institute of Marine Sciences in seminar room 222 in Morehead City, NC and live broadcast to UNC Department of Marine Sciences conference room 3204 on the 3rd floor of Murray Hall in Chapel Hill, NC. This event will be held on Wednesday, September 6th, 2017 from 9:00 am until 10:00 am.

Title: Tracking the sources and fates of fluorescent organic matter in the eutrophic, anthropogenically impacted Neuse River Estuary, NC

Abstract: The role of organic matter (OM) in aquatic systems has received increasing attention in the past few decades as a carbon substrate for bacterial degradation, a potential nutrient (as nitrogen, N) source for phytoplankton production, and as a factor in the cultural eutrophication of anthropogenically impacted systems. The proposed dissertation will constrain the role of terrestrially loaded and autochthonously produced OM in estuarine systems through environmental surveys and OM addition bioassays. Broad classes of terrestrial and autochthonous fluorescent OM will be identified and tracked using optical techniques (excitation emission matrices, EEMs, coupled with parallel factor analysis, PARAFAC) to better understand the sources, transport, and fate of fluorescent OM in these systems. The study will be conducted in the eutrophic Neuse River Estuary (NRE), NC which has been experiencing urbanization and agricultural development in its watershed since the 1970s. Despite successful reductions in total N loading due to the introduction of a total maximum daily N load (TMDL), the estuary still exhibits symptoms of eutrophication (nuisance phytoplankton blooms; water quality degradation; fish kills), making it an ideal study site to understand the role terrestrial and autochthonous fluorescent OM plays in eutrophication dynamics. An environmental survey was conducted from July 2015 to July 2016 and will allow for spatial and temporal analysis of terrestrial fluorescent OM loading and autochthonous fluorescent OM production in the system. Results will be compared to an environmental survey conducted following Hurricane Matthew from October – December 2016 to explore how extreme precipitation events alter terrestrial fluorescent OM loading and cycling in estuarine systems. Finally, OM addition bioassays will be used to understand the role terrestrial OM sources play in stimulating phytoplankton production in the N-limited NRE. Results from the proposed dissertation have important implications for the management and sustainability of eutrophying, estuarine systems worldwide and will allow for a better understanding of the role terrestrial and autochthonous fluorescent OM sources may play in eutrophication dynamics in these impaired systems.