Sin, Y. College of William & Mary, School of Marine Science/VIMS, yongsik@vims.edu
Wetzel, R. College of William & Mary, School of Marine Science/VIMS, dick@vims.edu
Anderson, I. C.. College of William & Mary, School of Marine Science/VIMS, iris@vims.edu

 
THE USE OF A PLANKTON ECOSYSTEM MODEL FOR THE STUDY OF SIZE-STRUCTURED PHYTOPLANKTON DYNAMICS IN THE YORK RIVER ESTUARY, VIRGINIA
 
A plankton ecosystem model was developed to investigate mechanisms controlling size-structured phytoplankton dynamics in the mesohaline zone of the York River estuary, Virginia. The model included 12 state variables in a unit volume (cubic m) describing the distribution of carbon and nutrients in the surface mixed layer. Groupings of autotrophs and heterotrophs were based on cell size and ecological hierarchy; mixotrophy was not considered. Forcing functions included incident radiation, temperature, wind stress, mean flow and tide which includes advective transport and turbulent mixing. The ecosystem model was developed in FORTRAN using differential equations that were solved using the 4th order Runge-Kutta technique. Model sensitivity tests showed that small cells (pico-, nano-sized) are more likely regulated by temperature and light whereas large cells (micro-sized) are regulated by physical processes such as advection and tidal mixing. Microphytoplankton blooms during winter-spring resulted from a combination of longitudinal advection and vertical diffusion of phytoplankton cells and nutrients. Model results supported the general view that phytoplankton dynamics are controlled by abiotic mechanisms (i.e. bottom-up control) rather than biotic, trophic interactions in the York River estuary, Virginia.
 
Day: Thursday, Feb. 4
Time: 11:30 - 11:45am
Location: Sweeney Center
 
Code: CS62TH1130S