Feeding, growth dynamics and behavior of the bioluminescent dinoflagellate, Polykrikos kofoidi




Schmidt, Richard Keith, 1969-

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The dinoflagellate Polykrikos kofoidi is a pseudocolonial, bioluminescent heterotrophic species which has been known to readily feed upon other nearshore dinoflagellate blooms, such as red tides. This heterotrophic dinoflagellate was found to feed preferentially on photosynthetic dinoflagellates with a diameter of 30 μm and greater, but at high food concentrations. For all food species tested, Gyrodinium dorsum, Gonyaulax polyedra and a 50/50 mixture (based on carbon content), growth rates reached maximal values at 4-6 mg C 1⁻¹ (μmax] = 0.8 d-1) . The feeding rate of P. kofoidi increased with food concentrations and did not appear to saturate at concentrations up to 8-10 mg C 1⁻¹, which was supported by encounter rates calculated for each food treatment. Encounters with food cells (cells/day) by each P. kofoidi were not significantly different (paired Student's t-test, α=0.05) from the number of cells ingested per day for each individual, which also indicates that P. kofoidi must contact a prey cell to feed and cannot locate prey using remote chemical cues in the water. A comparison of swimming behavior in the presence and absence of prey cells and prey exudate also supports the assumption of the inability of P. kofoidi to detect remote chemical cues in the water. The bioluminescent capacity of P. kofoidi exhibited a positive correlation with growth rate over varying food concentrations. The constant increase in ingestion of food, even in concentrations as high as 8-10 mg C 1⁻¹, coupled with a growth rate that exceeded that of its preferred food species, will allow P. kofoidi to exploit blooms of dinoflagellates and could serve as a biological control agent to help control red tides