AME 28:79-85 (2002)  -  doi:10.3354/ame028079

Grazing by microzooplankton on Pfiesteria piscicida cultures with different histories of toxicity

Diane K. Stoecker1,*, Matthew W. Parrow2, JoAnn M. Burkholder2, Howard B. Glasgow Jr.2

1University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, USA
2Center for Applied Aquatic Ecology, North Carolina State University, Raleigh, North Carolina 27695, USA

ABSTRACT: Susceptibility of actively toxic (TOX-A) zoospores, temporarily non-toxic (TOX-B) zoospores, and zoospores non-inducible to toxicity (NON-IND) of Pfiesteria piscicida to microzooplankton grazing was compared in a laboratory experiment. Zoospores from all cultures were ingested by microzooplankton, but community grazing coefficients for TOX-A were <20% of those for TOX-B or NON-IND zoospores in 6 h incubations. Tintinnids and strobilidiid ciliates that fed on P. piscicida declined in incubations containing TOX-A zoospores. There was no decline in a strombidiid ciliate or heterotrophic dinoflagellate populations that fed on TOX-A zoospores. These data suggest that, although microzooplankton grazing on non-toxic zoospores can be a significant source of mortality to planktonic populations of P. piscicida, grazing on toxic or very recently toxic zoospores is relatively low.

KEY WORDS: Pfiesteria piscicida · Zoospores · Toxicity · Microzooplankton · Grazing

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