Overview: In this project, the fellow will conduct a study of the dynamics of community structure of coastal benthic systems, in situ, and under hypoxic conditions, the role of physiological adaptations in maintaining benthic services and functions, and the economic cost of hypoxia. This work will be undertaken under the mentorship of Professor Cindy Lee Van Dover at the Marine Laboratory of the Nicholas School of the Environment, Duke University.
Coastal hypoxia can have negative consequences on benthic community structure and function. While the effects of hypoxia on benthic community structure are well understood, less well known are impacts to community function. At the onset of hypoxia, mobile fauna are displaced, and, as the severity and duration of hypoxia increase, community structure of non-mobile infauna degrades (i.e., loss of biodiversity, biomass, activity). Impacts of hypoxia can have ecosystem-level consequences, including reductions in benthic fisheries that depend on infauna for their nutrition (e.g., demersal fish and epibenthic crustacean predators); degradation of the infauna community also reduces bioturbation rates, altering rates of biogenic remineralization of nutrients and pollutant sequestration.
Intellectual Merit: This study will take advantage of comparative systems that experience sustained (Chesapeake Bay, VA) and intermittent (Neuse River, NC) seasonal hypoxia to answer the following questions: 1) What is the relationship between hypoxia and bioturbation rates under sustained and intermittent conditions of hypoxia? This question will be addressed through 12-months of benthic observations in two systems using time-series (hourly) sediment profile imaging (SPI) and environmental sensing systems, together with monthly replicate sampling for spatial characterization of bioturbation rates (sediment profiles) and community structure (sediment grabs). Study locations will be chosen based on the history of hypoxia in each system, using data from the Chesapeake Bay Benthic Monitoring and Neuse River Estuary Modeling and Monitoring Programs of the Chesapeake Bay Program and University of North Carolina Chapel Hill's Institute of Marine Science, respectively. 2) What is the relationship between hypoxia and physiological response of key system organisms? This relationship will be examined using respirometry and gene expression methodologies in two benthic polychaete species, and will test the hypothesis that there are significant differences in response between organisms cultured from Chesapeake Bay and the Neuse River. Cultured polychaetes from each system will be put through hypoxia trials using stop-flow respirometry to determine metabolic rate, O2 extraction, and the O2 saturation level that induces mortality. Subsamples of worms will be removed and frozen at intervals in the hypoxia trials for subsequent Restriction site Associated DNA sequencing to survey for differential gene expression. 3) What is the economic cost of coastal hypoxia. The fellow will develop a bioeconomic model that explores the economic costs of hypoxia in Chesapeake Bay by relating hypoxic affects to a benthic fishery (i.e. blue crabs), and compare those results with economic valuations of hypoxia previously conducted in the Neuse River.
Broader Impacts: Research results will be disseminated in the scientific literature and will provide new knowledge useful to coastal environmental managers. The fellow will expand efforts to broaden the participation of minorities in ocean science through mentoring programs at Duke University, in the ASLO Multicultural Program, and in the annual Youth Education Summit of the National Association of Black Scuba Divers, which targets grade school minorities with an interest in ocean science.
