FATTY-ACID COMPOSITION OF FRESH-WATER PHYTOPLANKTON DURING A RED TIDEEVENT

The fatty acid composition of phytoplankton in a freshwater reservoir in east Tennessee was investigated during a short-lived algal bloom. P hytoplankton were dominated by the euplankter dinoflagellate Peridinio psis penardii. The major fatty acids were (in decreasing order of abun dance), 16:1omega7, 16:0, 22:6omega3, 14:0, 20:5omega3, 24:1omega9, 16 :4omega1 and 16:3omega4. The phytoplankton lipids contain relatively l ow proportions of some of the typically major fatty acids of dinoflage llates (e.g. 18:1omega9 and 18:4omega3). Furthermore, the phytoplankto n lipids exhibited only trace amounts of 3,6,9,12,15-octadecapentaenoi c acid. Octadecapentaenoic acid (18:5omega3) is a predominant and pote ntially toxic fatty acid characteristic of dinoflagellates. This fatty acid profile differed substantially from those reported for marine an d cultivated dinoflagellate species.