A. Project Summary. ECOHAB-GOM: The ecology and oceanography of toxic Alexandrium blooms in the Gulf of Maine.

Principal Investigators: Donald. M. Anderson (Woods Hole Oceanographic Institution), David W. Townsend (University of Maine), James H. Churchill (Woods Hole Oceanographic Institution), John J. Cullen (Dalhousie University), Gregory J. Doucette (Medical Univ. of South Carolina), Wayne R. Geyer (Woods Hole Oceanographic Institution), Maureen D. Keller (Bigelow Laboratory for Ocean Sciences), Theodore C. Loder III (University of New Hampshire), Daniel R. Lynch (Dartmouth College), Jennifer L. Martin (Canadian Dept. of Fisheries and Oceans), Dennis J. McGillicuddy (Woods Hole Oceanographic Institution), John E. O'Reilly (National Marine Fisheries Service), Neal R. Pettigrew (University of Maine), Richard P. Signell (U.S. Geological Survey), Andrew C. Thomas (University of Maine), Jefferson T. Turner (University of Massachusetts Dartmouth).

Associate Investigator: John Hurst (State of Maine Dept. of Marine Resources).

Proposed Cost: $5,100,328 Budget Period: September 1, 1997 - August 31, 2002

Harmful algal blooms, commonly called "red tides" or HABs, are a serious economic and public health problem throughout the world. In the U.S., the most serious HAB problem is paralytic shellfish poisoning (PSP), a potentially fatal neurological disorder caused by human ingestion of shellfish that accumulate toxins as they feed on dinoflagellates of the genus Alexandrium. These organisms cause human illness and death due to PSP, repeated shellfish harvest quarantines, and the mortality of fish and marine mammals. This phenomenon, which affects thousands of miles of U.S. coastline and numerous fisheries resources, has expanded dramatically in the last two decades, especially in the Gulf of Maine. Here we propose ECOHAB-GOM, a project that addresses several fundamental issues regarding Alexandrium blooms in the Gulf of Maine: 1) the source of the Alexandrium cells that appear in the fresh water plumes in the western Maine coastal current (WMCC); 2) Alexandrium cell distribution and dynamics in the eastern Maine coastal current (EMCC); and 3) linkages among blooms in the WMCC, the EMCC and on Georges Bank. Utilizing a combination of numerical modeling, hydrographic, chemical, and biological measurements, moored and drifting current measurements, and satellite imagery, we will characterize the structure, variability and autecology of the major Alexandrium habitats in the Gulf of Maine.

In the western Gulf, Alexandrium blooms and patterns of PSP have been linked to a coastal current or plume of low salinity river outflow (the WMCC). One major project goal is to investigate the area implicated as the major "source region" for the toxic cells that populate that coastal current. We will elucidate the biological, chemical, and physical processes that control bloom initiation and development, the delivery of cells from that source region into the WMCC, and the manner in which late-season, localized blooms are retained there to re-seed future blooms with cysts. Our second major set of objectives is to characterize the linkage between toxic blooms and the EMCC, to investigate the role of tidal mixing, frontal systems, and upwelling / downwelling in Alexandrium dynamics, and to define the linkage between EMCC Alexandrium populations and those in both the WMCC (downstream) and the Bay of Fundy (upstream). Another project element will examine toxicity on Georges Bank, a rich shellfish resource that is a downstream delivery site for toxic cells from both coastal currents. A unique set of "process" studies will focus on discrete blooms or patches of cells and quantify such parameters as in situ growth rates and grazing losses of Alexandrium, the nutritional physiology, vertical migration behavior and transport of this species, the partitioning of toxins within the food web, and the extent to which mixotrophy supplements photosynthesis. A hierarchy of coupled physical-biological models will be used together with ECOHAB-GOM data for investigation of:

1) detailed structure within each habitat; 2) interconnections among habitats; and 3) the role of the larger Gulf-scale circulation in the long-term maintenance of Alexandrium populations in the region. Advances in our understanding of the underlying mechanisms controlling the population dynamics of Alexandrium will be distilled into simple predictive models of PSP toxicity which can be driven by a relatively small number of observable parameters. ECOHAB-GOM is thus a combined modeling/observational program, utilizing the most current and innovative technologies in an approach commensurate with the multiple scales and oceanographic complexity of PSP phenomena in the Gulf of Maine.