Shellfish Toxicity and Dormant Cysts in Toxic Dinoflagellate Blooms

Several of the dinoflagellates responsible for toxic blooms include a dormant cyst stage in their life cycles. These resistant cells have a variety of potential functions in the overall ecology of the toxic dinoflagellates. As Wall ( 1 ) discussed, cysts can theoretically act as "seed" populations to initiate blooms, as a survival mechanism through environmental extremes, as agents for species dispersal, and as means for genetic recombination through sexuality. Two additional functions can be added to this list: cysts can be direct sources of toxicity, and their formation can be a major factor in bloom termination. The purpose of this paper is to examine our present knowledge of the cysts of the toxic Gonyaulax species to see whether these hypothetical considerations are valid representations of the actual roles cysts play in toxic dinoflagellate blooms and shellfish toxicity.