Title: Patterns and Impacts of Microalgal Blooms in Lower Chesapeake Bay
Speaker: Dr. Kimberly Reece (Chair and Professor, Aquatic Health Sciences, Virginia Institute of Marine Science)
Abstract: A relatively consistent pattern of microalgal blooms takes place in lower Chesapeake Bay, although year to year variations in rainfall, temperature, wind, salinity and other environmental parameters can effect timing, densities, distributions, and even bloom occurrence in a given year. Late summer blooms of the harmful algal bloom (HAB) species Margalefidinium (formerly Cochlodinium) polykrikoides have happened almost annually for many decades and for the past decade the HAB species Alexandrium monilatum also has been blooming in the region. Both species have been increasing in density and distribution throughout lower Chesapeake Bay in recent years. A predictable population progression typically occurs with peak cell concentrations of M. polykrikoides followed a few weeks later by peak concentrations of A. monilatum. Reports of juvenile oyster mortalities from local shellfish aquaculturists during and immediately following these blooms have prompted studies with adult and juvenile oysters with an aim toward identifying mitigation strategies. Field studies are examining the impacts of these HABs and other stressors, including temperature and low dissolved oxygen, on various oyster life stages using different grow-out strategies. The toxin goniodomin A was isolated from water samples collected during A. monilatum blooms and was found to cause rapid mortality in larval shellfish and finfish in laboratory studies. Field studies showed that mortality was slightly higher for oysters grown intertidally at bloom exposed sites during the blooms than for those grown at a reference site. Bottom sediment samples were collected from 2014-2018 to map and quantify A. monilatum cysts by qPCR and cysts were found to be widespread in the region with increasing densities over time.
Host: Dr. Colleen Burge
