Time courses of intracellular and extracellular lipid classes in batch cultures of the toxic dinoflagellate, Gymnodinium cf. nagasakiense

The effect of temperature and light on lipid production was determined for an isolate of Gymnodinium cf. nagasakiense which is known to be toxic. Samples were taken in a time course in cultures grown at 13 or 18°C and at 35 or 75 μE•m−2•s−1. The lipid class composition of Gymnodinium cf. nagasakiense cells and their exudates were analyzed with the Chromarod-Iatroscan system. The main intracellular lipid class, glycolipid, was present at similar concentrations in the cells in all three cultures. Maxima in intracellular concentrations of triacylglycerol, and minima in intracellular free fatty acid concentrations occurred near the time of maximum culture density. Dissolved free fatty acid concentrations were higher during the first 20 days than in the following 10 days of each culture. The culture grown at 13°C had the highest intracellular triacylglycerol concentration and the highest extracellular free fatty acid concentration. The culture grown at 35 μE•m−2•s−1 had the highest extracellular glycolipid concentration. Gas chromatographic analyses at the end of the growth experiments showed that pentaenoic fatty acids consisting mainly of 18:5n3 were twice as prominent in cells grown at the lower light level. However, the amount of 18:5n3 released into the surrounding medium in this culture was negligible.