Mixotrophy and Nitrogen Uptake by Pfiesteria Piscicida (Dinophyceae)

Abstract

The nutritional versatility of dinoflagellates is a complicating factor in identifying potential links between nutrient eurichment and the proliferation of harmful algal bloom. For exmaple, although dinoflagellates associated with hamful algal blooms (e.g. red tides) are generally considered to be phototrophic and we inorganic nutrients such as nitrate or phosphate, many of these species also have pronounced heterotrophic capabilities either as osmorophs or phagotrophs. Recently, the widespread occurrence of the heterotmpbic toxic dinoflagellate Pfiesteria piscidia Steidinger et Burkholder, has been documented in turbid estuarine waters. Pfiesteria piscidia has a relatively proficient gmziug ability, but also has an ability to function as a phototroph by acquiring chloroplasts from algal prey, a process termed kleptoplastidy. We tested the abilily df kleptoplastidic P. piscicida to take up ¹⁵N-labled NH^+₄, NO^-₃, urea, or glutamate. The photosynthetic activity of these cultures was verified,inpart by use of the fluorochrome, primulin which indicated a positive relationship between photosynthetic starch production and growth irradiance. All four N substrates were taken up by P. piscicido, and the highest uptake rates were in the range cited for phytoplankton aad were similar, to N uptake estimate for phototrophic P. piscicido. The demonstration of direct nutrient acquisition by kleptoplastidic P. piscicido suggests that the response of the dinoflagellate to nutrient enrichment complex, and that the specified pathway of nutrient stimulation (e.g. indirect stimulation through enhancement of phytoplankton prey abundance vs. direct stimulation by saprotrophic nutrient uptake) may depend on P. piscicida's nutrient state (phagotrophy vs. phototrophy).

Citation

Lewitus, Alan J.; Willis, Bonnie M.; Hayes, Kenneth C.; Burkholder, JoAnn M.; Gasgow, Howard B., Jr.; Gilbert, Patricia M.; Burke, Marianne K. 1999. Mixotrophy and Nitrogen Uptake by Pfiesteria Piscicida (Dinophyceae). J. Phycol. 35, 1430-1437 (1999)