Autoecology and morphological variability of Dinophysis sacculus (Dinophyceae: Dinophysiaceae) in a Mediterranean lagoon.

Dinophysis sacculus Stein (Dinophyceae) is a potential producer of diarrhetic shellfish poisoning (DSP). Population dynamics of this dinoflagellate was followed in the Varano lagoon, SE Italy, with the objective of determining the seasonal abundance of Dinophysis sacculus and the relationship to environmental factors. The seasonal occurrence of this dinoflagellate showed a rather wide temporal distribution and increases in cell numbers was observed in late June and November. Dinophysis numbers seasonal changes appeared to be dependent on chemico-physical factors and dissolved nutrients. Three morphologically distinct forms of Dinophysis sacculus were found during the sampling period (March 1997 – February 1998) related to the life history of the species and not to environmental conditions. In this mussel fishery, D. sacculus presence and proliferation was not associated with biotoxicity.