GREEN AND BLUE FLUORESCING DINOFLAGELLATES IN BAHAMIAN WATERS

At three stations in Bahamas waters, in 1989, 15 to 30% of all the dinoflagellates > 20-mu-m diameter observed in near-surface waters fluoresced green under blue excitation light, 55 to 66% fluoresced red, and the remainder did not fluroesce at all. The abundance of these green-fluorescing dinoflagellates ranged from ca 5 to 10 cells l-1 at the study sites. Under UV excitation, however, the dinoflagellates had a blue to blue-green appearance. Almost all the blue-green fluorescing dinoflagellates appeared to be heterotrophic, except for one species, Phalacroma rapa Stein, which also contained red-fluorescing (under blue light) chlorophyll a. The emission spectra from all species examined were of three basic types. Type 1 typically had two fluorescence emission peaks (ca 440 and ca 510 nm). Type 2 spectra possessed one sharp peak at 495 nm. Spectra belonging to Type 3 had a broad peak around 470 to 480 nm. The green fluorescence thus is likely caused by different substances in individual species. The attempt to reconstitute observed spectra with nicotinamide adenine dinucleotide (NADH) and riboflavin 5'-phosphate (FMN) solutions was unsuccessful.