Large blooms of Cochlodinium polykrikoides have occurred throughout the lower Chesapeake Bay and its tributaries in recent decades and appear to be followed by increasingly intense blooms of the ichthyotoxic Alexandrium monilatum. There is limited knowledge concerning the timing and nature of these blooms, which this project seeks to overcome with a retrospective analysis of physical and biological conditions associated with the blooms coupled to field and laboratory efforts to understand controls on HAB seed germination and growth. A modeling tool will integrate knowledge from the retrospective analysis with formulations for mixotrophic growth and vertical migration to determine how climate variability affects blooms. 

Why We Care

Massive, months-long blooms of the dinoflagellate, Cochlodinium polykrikoides have occurred throughout lower Chesapeake Bay and its tributaries in most of the last 20 years and for the last eight years, subsequent blooms of the toxic Alexandrium monilatum have been increasing in intensity and duration. Despite their widespread and annual occurrence, efforts to prevent, control or mitigate blooms of these species have been stymied because of limited understanding of how and where blooms initiate and the factors that contribute to their ecosystem domination once blooms emerge. While mitigation and control of harmful algal bloom (HAB) proliferation is difficult in most situations, the localized nature of C. polykrikoides and A. monilatum bloom initiation provides the possibility of developing mitigation strategies to prevent these blooms. However, this requires understanding the factors contributing to bloom initiation, transport, magnitude, and duration.

Effective HAB prediction, management and regulatory interventions are hindered by the lack of a predictive understanding of how biological and physiological controls on bloom organisms, climatological and meteorological forcing, and estuarine circulation combine to control initiation and proliferation of blooms temporally and spatially.

What We Are Doing

This study is developed around a conceptual model of C. polykrikoides and A. monilatum blooms. The data collection and analyses are designed to focus on processes believed to be integral to bloom initiation and growth and are necessary to build a predictive understanding and model of bloom formation. Data collected and existing data will be incorporated into a one dimensional coupled physical-biological numerical model that will provide a framework for testing hypotheses about bloom processes and synthesis and integration of new and existing data sets. The goal is to provide a basis for a predictive model for HAB development that can be used by managers to develop prevention and mitigation strategies.

To address fundamental gaps in knowledge, a combined observational and modeling study of a mid-Atlantic estuarine system impacted by blooms of C.polykrikoides and A. monilatum will be undertaken to determine: 1) meteorological, nutritional, and physical parameters governing bloom initiation, growth and proliferation of these organisms in a lower Chesapeake Bay estuary; 2) environmental triggers for excystment in laboratory and natural populations of C. polykrikoides and A. monilatum; 3) how behaviors, alternative metabolisms, and bottom-up controls contribute to initiation and maintenance of C. polykrikoides and A. monilatum blooms under field and laboratory conditions; 4) how grazing and top-down control modulates C. polykrikoides and A. monilatum population growth and expansion; 5) how climate variability affects bloom initiation, magnitude and duration. This model and project data will be shared with managers via the VA Harmful Algal Bloom Task Force, a collection of stakeholders and managers from the region, and VA Department of Environmental Quality.

Dr. Margaret Mulholland of Old Dominion University leads this project. Co-leads are Drs. Eileen Hofmann (Old Dominion University) and John Klinck (Old Dominion University). The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Bloom (ECOHAB) Program.