A Mixotropic Model for Toxigenic Karlodinimum veneficum Blooms in Chesapeake Bay

NOAA Science Seminar Series
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Title: A Mixotropic Model for Toxigenic Karlodinimum veneficum Blooms in Chesapeake Bay  

Presenters: 
Ming Li, Professor, University of Maryland Center for Environmental Science and
Patricia M. Glibert, Professor, University of Maryland Center for Environmental Science

Sponsor: NOAA's National Ocean Service (NOS) Science Seminar Series

Seminar Contact: Quay.Dortch@noaa.gov and Tracy.Gill@noaa.gov 

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Abstract: Blooms of dinoflagellate Karlodinium veneficumare widely distributed in estuarine and coastal waters and have been found to cause fish kills worldwide. K. veneficum has a mixed nutritional mode and relies on both photosynthesis and phagotrophy for growth. Mixotrophic plankton are ubiquitous in the ocean and fundamentally change the flows of energy in the marine food chain, but their important role in marine ecology has only been recognized over the past decade. Many Harmful Algal Bloom (HAB)species deploy a mixotrophic strategy to gain a competitive advantage, but a mechanistic understanding of these blooms is often lacking, making it challenging to predict the HAB impacts on marine ecosystem and human health. Here we report the development of 3D coupled hydrodynamic (ROMS)-biogeochemical(RCA)-mixotrophic (MIXO) models of K. veneficum and their prey Cryptomonas in Chesapeake Bay. MIXOis based on the “perfect beast” model of Flynn and Mitra and has been calibrated against physiological experiments of these species grown inmixed-batch cultures and under varying nitrogen (N):phosphorus (P)stoichiometry ratios. Hindcast simulations showed that K. veneficum blooms occurred during June-August and were confined to the upper and middle Bay. The numbers of prey ingested by K. veneficum varied from 0.1 to 0.6 per day and the food vacuole content reached up to 50% of the core mixotroph biomass. The ingestion rate increased with prey density but dropped sharply when P:N ratio exceeded 0.03, indicating that K. veneficum only switched to mixotrophic feeding in phosphorus-deficient waters. The digestion rate increased with both the food vacuole content and temperature. Autotrophic growth dominated in late spring and early fall but heterotrophic growth dominated during the summer. The modeling analysis affirms K. veneficum as a phagotropic ‘algae’ which is primarily photosynthetic but switches to mixotrophic feeding under nutrient deficient conditions.

Bio(s): Ming Li is a Professor at the University of Maryland Center for Environmental Science. He obtained B.Eng from Hohai University and Ph.D from University of Oxford. His research spans several areas in physical oceanography, including estuarine and coastal dynamics, sea level rise, and storm surge. He is actively engaged in interdisciplinary research such as hypoxia, ocean acidification, and harmful algal blooms. A major focus of his current research is the regional impact of climate change.

Patricia Glibert is also a Professor with the University of Maryland Center for Environmental Science. She obtained a B.A. from Skidmore College, an M.S. from the University of New Hampshire and a Ph.D. from Harvard University. She also holds an Honorary Doctorate from Linnaeus University, Sweden. Her work is focused on the fate and transformation of nutrients in marine and estuarine waters, eutrophication, and the ecology and physiology of phytoplankton, including harmful algae. 

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{Ming Li, Professor, University of Maryland Center for Environmental Science and Patricia M. Glibert, Professor, University of Maryland Center for Environmental Science}