Cysts of Danish Gymnodinium nolleri ellegaard et moestrup sp. ined. (Dinophyceae): Studies on encystment, excystment and toxicity

Abstract

Life cycle dynamics of Gymnodinium nolleri Ellegaard et Moestrup sp. ined. were studied under different temperature and nutrient conditions. Five culture strains originating from cysts found in Danish marine sediments were used for the experiments. Both encystment and excystment were found to vary with temperature. Maximal encystment occurred at 22-28°C, with no cysts formed below 13°C or above 33°C. Cyst production was slightly higher under phosphorus limitation than under combined nitrogen and phosphorus limitation. Maximal excystment occurred at 26.5°C with negligible excystment under 11°C and over 35°C. The resting period for cyst maturation was typically 3-4 weeks. Cysts produced under both phosphorus and nitrogen limitation were tested for paralytic shellfish poisoning (PSP) toxins by HPLC, and none were detected. It remains unclear why vegetative cells of this species have not yet been recorded in plankton samples from Scandinavia, despite the widespread distribution of the cysts.