JPR Advance Access originally published online on August 31, 2004
Journal of Plankton Research 2004 26(12):1507-1514; doi:10.1093/plankt/fbh139
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Journal of Plankton Research Vol. 26 No. 12 © Oxford University Press 2004; all rights reserved
Potential toxicity of chrysophytes affiliated with Poterioochromonas and related Spumella-like flagellates
Institute for Limnology, Austrian Academy of Sciences, Mondseestr. 9, 5310 Mondsee, Austria
* Corresponding Author: jens.boenigk{at}oeaw.ac.at
Received April 29, 2004; accepted in principle August 11, 2004; accepted for publication August 23, 2004; published online August 31, 2004
The chrysophyte genera Poterioochromonas and Ochromonas and their heterotrophic analogons, i.e. the Spumella-like flagellates, account for a significant and often dominating fraction of the pelagic nanoplankton. Even though several osmotrophically and autotrophically grown strains of Ochromonas and Poterioochromonas are assumed to produce toxins, the potential toxicity has been investigated neither for its association with bacterivorous nutrition nor within the related exclusively heterotrophic Spumella-like flagellates. We investigated the toxic potential of several flagellate strains using cultures of flagellates, cell extracts and filtrate of flagellate cultures. The effect on potential predators was exemplarily tested for the cladoceran Daphnia magna and the rotifer Platyias sp. All tested heterotrophic and mixotrophic flagellate strains were toxic to zooplankton at abundances exceeding 104 flagellates mL1. For the rotifers, survival on any of the flagellate strains was significantly lower than that in the control treatment (P < 0.001) already after 24 h. We conclude that (i) Spumella-like flagellates can be toxic to zooplankton, (ii) all tested flagellates, i.e. heterotrophic and mixotrophic flagellates, feeding phagotrophically can be toxic to zooplankton and (iii) sublethal effects may be observed at typical field abundances, even though acute toxicity seems to be restricted to flagellate abundances observed only at peak events.