Long-chain alkenes and alkenones in the marine coccolithophorid Emiliania huxleyi

Abstract Very long-chain n -alkenes and n -alkenones have been identified in the ubiquitous marine alga Emiliania huxleyi . The alkenes range from C 31 to C 38 and are almost exclusively odd-chain. Dienes, trienes and tetraenes were identified but no monoenes were found. The ketones ranged from C 37 to C 39 and consisted of both alken-2-ones and alken-3-ones, with trienes more abundant than dienes. Examination of three different forms of the alga, i.e. motile, sessile and coccolith, indicated that these ketones are formed throughout the growth cycle with only minor variations in the relative proportions of the individual compounds. Although these novel compounds have not been reported previously in organisms, they are widespread in marine sediments and may be useful biological markers for E. huxleyi input to sediments.