A survey of the sterol composition of the marine dinoflagellates Karenia brevis, Karenia mikimotoi, and Karlodinium micrum distribution of sterols within other members of the class Dinophyceae

The sterol composition of different marine microalgae has been examined to determine the utility of sterols as biomarkers to distinguish members of various algal classes. For example, members of the class Dinophyceae possess certain 4-methyl sterols, such as dinosterol, which are rarely found in other classes of algae. The ability to use sterol biomarkers to distinguish certain dinoflagellates such as the toxic species Karenia brevis Hansen and Moestrup, responsible for red tide events in the Gulf of Mexico, from other species within the same class would be of considerable scientific and economic value. Karenia brevis has been shown by others to possess two major sterols, (24S)-4alpha-methyl-5alpha-ergosta 8(14),22-dien-3beta-ol (ED) and its 27-nor derivative (NED), having novel structures not previously known to be present in other dinoflagellates. This prompted the present study of the sterol signatures of more than 40 dinoflagellates. In this survey, sterols with the properties of ED and NED were found in cultures of K brevis and shown also to be the principal sterols of Karenia mikimotoi Hansen and Moestrup and Karlodinium micrum Larsen, two dinoflagellates closely related to K brevis. They are also found as minor components of the more complex sterol profiles of other members of the Gymnodinium/Peridinium/Prorocentrum (GPP) taxonomic group. The distribution of these sterols is consistent with the known close relationship between K brevis, K mikimotoi, and K micrum and serves to limit the use of these sterols as lipid biomarkers to a few related species of dinoflagellates.