Blooms of the Toxic Dinoflagellate Alexandrium fundyense in the Gulf of Maine: Investigations using a Physical-Biological Model

Charles A. Stock, Ph.D., 2005
Dennis McGillicuddy, Advisor

Blooms of the toxic dinoflagellate Alexandrium fundyense are annually recurrent in the western Gulf of Maine (WGOM) and pose a serious economic and public health threat. In this thesis, a biological model of the A. fundyense life cycle developed from laboratory and field data is combined with a circulation model to test hypotheses concerning the factors governing A. fundyense blooms in the springs of 1993 and 1994. Several biological model structures are tested against the 1993 observations using the method of maximum likelihood. Analysis suggests that either nitrogen limitation or mortality is needed to match observed patterns. Application of 1993 optimized values to 1994 shows similar fit is maintained only for those runs with nitrogen limitation. Model diagnosis suggests that cysts germinating offshore of Casco Bay provide a plausible source of cells for the blooms, although inputs from the eastern Gulf of Maine become significant as the season progresses. Net growth rates are generally low and have a limited influence on bloom magnitude. The model suggests that differences in shellfish toxicity during the two years result primarily from differences in the wind and its influence on along and cross-shore transport of cells.