Dinoflagellate Blooms and Physical Systems in the Gulf of Maine
1990
Franks, Peter J.
Blooms of the toxic dinoflagellate Alexandrium tamarense have been nearly annual occurrences along the coast of Maine, New Hampshire and Massachusetts since 1972. However, the mechanisms controlling the timing and spread of these blooms have not been well understood. Based on intense hydrographic and biological sampling from 1987 to 1989 in the affected region, I concluded that blooms of A. tamartense were advected alongshore in a coastally trapped buoyant plume formed by the outflow of the Androscoggin and Kennebec Rivers in Maine. Tests of this 'plume advection' hypothesis using historical records of shellfish toxicity, wind speed and direction, and river flow rates supported its validity. The plume-advection hypothesis was found to explain many of the details of the timing and location of toxic outbreaks. These included the annual north-to-south progression of toxicity, the relationship of the speed of the alongshore progression of toxicity with river flow rates, the influence of alongshore wind stress on the distribution of low-salinity water and A. tamarense cells, and the presence of a toxin-free zone south of Cape Ann, MA.
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