Aquatic Sciences Meeting, Albuquerque 2001

PC01 Harmful Algal Blooms

Date: Tuesday, February 13, 2001

Location: Southwest Hall

Clough, J, S, Western Washington University, Bellingham, USA, cloughj@cc.wwu.edu

EFFECTS OF HETEROSIGMA AKASHIWO ON GROWTH AND GRAZING RATES OF PROTOZOANS

Protozoans have been demonstrated to be the major grazers of algae in many regions, but the formation of dense harmful algal blooms suggests an uncoupling of this relationship. A possible reason for this discrepancy is inhibition of grazing by the bloom-forming alga. To examine this possibility, two strains of Heterosigma akashiwo (CCMP452 and CCMP1914) were fed, alone and in combination with a preferred food, to a variety of ciliate and dinoflagellate grazers. Growth and ingestion rates were measured and compared to controls fed the preferred food alone or starved. Preliminary results indicate that growth of Coxliella sp., a tintinnid ciliate, is inhibited in treatments containing Heterosigma akashiwo, even when there is a sufficient amount of preferred food for ciliate growth. If this effect is also seen in other taxa, it suggests interesting consequences for trophic structures in coastal waters during a Heterosigma bloom.

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Aquatic Sciences Meeting, Albuquerque 2001

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