CYSTS OF DANISH GYMNODINIUM-NOLLERI ELLEGAARD ET MOESTRUP SP. INED. (DINOPHYCEAE) - STUDIES ON ENCYSTMENT, EXCYSTMENT AND TOXICITY

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