[PAST EVENT] Where does oyster poop go? Investigations of bivalve biodeposit dispersal from aquaculture farms

April 12, 2013
VIMS - Watermen's Hall, McHugh Auditorium
1375 Greate Road
Gloucester Point, VA 23062Map this location
Presenter: Dr. Larry Sanford, Professor at the University of Maryland Center for Environmental Sciences

Reception at 3:00 p.m. in the lobby of Watermen's Hall
Seminar from 3:30 p.m. to 4:30 p.m. in McHugh Auditorium

Dr. Sanford is a 1978 graduate of Brown University where he majored in Mechanical Engineering. He earned his Ph.D. in Oceanographic Engineering in 1984 from the Joint Program in Oceanography and Oceanographic Engineering between the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution. He joined the University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, MD, in 1984 as a Postdoctoral Research Associate. He was promoted to Assistant Professor in 1987, Associate Professor in 1993, and Professor in 2001. His general research interests are in fine sediment transport processes, coastal and estuarine physical oceanography, waves, and turbulence. He has a special interest in interdisciplinary studies involving interactions between fluid flow and estuarine ecology. He also has a special interest in collaborating with VIMS colleagues, having driven around Chesapeake Bay on numerous occasions in order to do so.

Bivalve aquaculture relies on naturally occurring phytoplankton as a food source, thereby avoiding external nutrient inputs associated with finfish aquaculture. However, high filtration rates and concentrated biomass of bivalves focus intense particle deposition on surrounding sediments, with potential adverse environmental impacts. We studied seasonal sediment-transport processes responsible for dispersal of biodeposits from the vicinity of an eastern oyster farm in the lower Choptank River, MD, USA. The farm is situated near the upriver tip of a headland in approximately 1 m of water. Approximately 2 million 1-yr old oysters lead to up to 1 cm per day local sediment accretion in summer. We performed sediment and bathymetric surveys, deployed arrays of current meters, wave gauges, and sediment traps, measured settling velocities and erodibility, modeled tidal flows and wind-waves, modeled particle dispersal, and measured/modeled benthic fluxes in and around the farm. Results indicate that the site is ebb-dominated, tending to disperse biodeposits towards the open estuary. However, tidal currents alone are not competent to transport the biodeposits beyond the near-field of the farm. Episodic wave events likely provide additional energy needed for dispersal and minimization of local impacts. Significant dispersal is required to match measured and modeled benthic fluxes.

[[seitz, Rochelle Seitz]] at 804-684-7698