Center for Coastal Physical Oceanography & ODU Resilience Collaborative

Fall 2019 Seminar Series


Brynn Pecher

Monday, November 11, 2019
3:30 PM
Conference Center, Innovation Research Building II
4211 Monarch Way, Norfolk, VA 23508


The occurrence and progression of blooms of the harmful algae, Margalefidinium polykrikoides, in the lower Chesapeake Bay show considerable interannual variability. The relative contributions of environmental conditions in producing the observed variability are evaluated with a three-component, time-dependent model that uses observed time series of light, temperature, nutrients, and meteorological conditions to simulate algal growth and biomass. The model components include cysts and algal cells in the water column and a bottom reservoir of cysts. The algal growth parameterization includes autotrophic and mixotrophic processes. The cysts suspended in the water column undergo excystment, which adds algal cells, and encystment, which removes algal cells. Cysts that sink to the bottom can be resuspended via wind events. The model parameterizations are constrained by field and laboratory measurements of Margalefidinium polykrikoides processes. The simulated time evolution of algal production follows the timing and magnitude of the observed bloom cycle of rapid growth, persistence, and decay. For optimal nutrient conditions, the bloom is constrained by temperature, the degree of mixotrophy, and the rates of excystment and encystment. The onset of a bloom occurs at 23°C to 24°C and maximum growth occurs at 26°C to 28°C. Variability in bloom maximum concentrations is related to temperature fluctuations. Nutrient limitation reduces the magnitude of the bloom and shifts the timing of the maximum concentration. This model provides a preliminary step towards development of a tool that can be used to assess the potential for harmful algal blooms in the lower Chesapeake Bay.


Brynn (Davis) Pecher is a research associate at the Center for Coastal Physical Oceanography. She received her B.S. degree in Ocean, Earth and Atmospheric Sciences (Biological Oceanography concentration) in 2014 from Old Dominion University and her M.S. degree in Ocean, Earth and Atmospheric Sciences (Biological and Physical Oceanography concentrations) from Old Dominion University in 2016 under the supervision of Dr. Eileen E. Hofmann. Brynn's research is focused on the development of a biological model for understanding the environmental drivers that induce local Margalefidinium polykrikoides blooms in the Lafayette River. Aside from her current project, her interests include the biological relationships of Southern Ocean food webs, with emphasis on krill, and the Antarctic silverfish in the Ross Sea, Antarctica and understanding their distributions in the newly established Marine Protected Area.

Reception before seminar at 3:00 PM

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Innovation Research Park Building I
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