LEBLOND, JEFFREY D.1* and PETER J. CHAPMAN2. 1Department of Biology, P.O. Box 60, Middle Tennessee State University, Murfreesboro, TN 37132; 2United States Environmental Protection Agency, Gulf Ecology Division, National Health Effects and Environment Research Laboratory, 1 Sabine Island Dr., Gulf Breeze, FL 32561. - Lipid biomarker analysis of the toxic dinoflagellate Pfiesteria piscicida : Distribution of sterols and fatty acids within the class Dinophyceae.
Within United States waters, regular blooms of harmful dinoflagellates
occur in the Gulf of Mexico and Chesapeake Bay regions. Although the
causes of blooms are not fully understood, events in Gulf of Mexico
waters have been recorded for over thirty years, and are almost
exclusively caused by the photosynthetic dinoflagellate, Karenia
brevis . Conversely, blooms in the Chesapeake Bay region, caused
by the heterotrophic dinoflagellate Pfiesteria piscicida ,
appear to be a relatively new phenomenon, and are hypothesized to be
linked to an increase in nutrient-rich runoff from chemical plants and
livestock farms along tributaries leading into the Chesapeake. Despite
the environmental, economic, and human health relevance of P.
piscicida , there appears to be no published work on the
characterization of its lipid composition. The objective of this study
was, therefore, to examine the sterol and fatty acid composition of
cultured P. piscicida isolates as a precursor to eventual
field studies of blooms of this organism. GC/MS analysis of
trimethylsilyl ether derivatives of sterols in free sterol and sterol
ester fractions revealed that the overwhelming majority of sterols was
found as free sterols. Furthermore, free sterols were found to
resemble those of other dinoflagellates, with the dominant compound
being the common dinoflagellate sterol, dinosterol; a number of other
4-methyl sterols common to other dinoflagellates were also identified.
The fatty acids of P. piscicida were found to be primarily
associated with a fraction containing cellular membrane phospholipids;
small amounts of the recently described highly-unsaturated fatty
acids, octacosaoctaenoic acid [28:8(n-3)] and octacosaheptaenoic acid
[28:7(n-6)], were observed in this fraction. The dominant fatty acid
(approximately 40-60% of the phospholipid fatty acids) was
docosahexaenoic acid [22:6(n-3)]. Unlike K. brevis (see
accompanying poster), P. piscicida does not appear to possess
significant amounts of unusual sterols or fatty acids which may serve
as potential biomarkers for this organism.
Key words: Pfiesteria , algae, dinoflagellate, fatty acids, lipids, sterols