THE LIPID-COMPOSITION OF THE COCCOLITHOPHORE EMILIANIA-HUXLEYI AND ITS POSSIBLE ECOPHYSIOLOGICAL SIGNIFICANCE

The lipid class and fatty acid composition of eight geographically dis perse isolates of Emiliania huxleyi, grown under 12 h L:D cycles and h arvested during logarithmic and stationary growth phases, were examine d. Cell size and chlorophyll content tended to decrease from logarithm ic to stationary growth phase, Methyl and ethyl ketones were the domin ant lipid classes, although proportions exhibited no clear pattern eit her between strains or growth phases. Neutral lipid hardly accumulated over the course of the growth experiments, and triacylglycerol was ei ther absent or only present at low levels. In all strains with the exc eption of a South African isolate, levels of total fatty acid per cell decreased markedly between logarithmic and stationary phases, primari ly attributable to reductions in the levels of saturated and monounsat urated fatty acids. Major fatty acids in all strains during both growt h phases were 14:0, 16:0, 18:1 (n-9), 18:4 (n-3), 18:5 (n-3) and 22:6 (n-3). Although all strains were rich in polyunsaturated fatty acids ( 47-72% of total fatty acids) stationary phase cultures consistently co ntained the highest proportions. The polyunsaturated fatty acid docosa hexanoic acid (22:6, n-3) was the most abundant fatty acid in all stra ins, comprising a maximum of 38 . 4% of total fatty acids in strain M1 81 during stationary phase. Multivariate analysis (PCA) allowed logari thmic and stationary phase cultures to be distinguished although no ob vious intra-isolate variability was apparent. The results are discusse d in terms of the importance of lipids for the ecophysiology of E. hux leyi and the role of this dominant coccolithophore in the marine food chain.