Aquatic Sciences Meeting, Albuquerque 2001

SS20 Biological Control of Harmful Algal Blooms: Role of Grazers, Parasites, Viruses and Bacteria

Date: Monday, February 12, 2001, Time: 4:30:00 PM

Location: Cochiti/Taos

Reckermann, M, , FTZ Westcoast of Kiel University, Buesum, Germany, recker@ftz-west.uni-kiel.de

Tillmann, U, , Alfred-Wegener-Institute, Bremerhaven, Germany, utillmann@awi-bremerhaven.de

Grazing impact on the toxic raphidophyte Fibrocapsa japonica by natural zooplankton communities

The toxic raphidophyte flagellate Fibrocapsa japonica appears in European waters in increasing numbers. To estimate the extent of biological control of F. japonica by grazing in situ, we carried out combined laboratory and field experiments with natural grazer populations (individually picked copepods and natural mixtures from 200µm net hauls). Grazing on F. japonica was positive in both experiments, with a maximum ingestion rate rate of 2733 cells / copepod * d (resp. 1.32 µg C / copepod * d) in the experiment with individual copepods as grazers. In the second experiment, F. japonica was added to natural North Sea water and exposed to different grazer size classes. Grazing was highest in the water with mesozooplankton added (3110 cells / grazer * d, resp. 1.50 µg C / grazer * d), but also high in the microzooplankton (<200µm) fraction. F. japonica cell numbers in the size fraction <20µm did not significantly change relative to the control (GFF filtered experimental water). It is concluded that zooplankton may significantly contribute to the biological control of F. japonica in North Sea waters.

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Aquatic Sciences Meeting, Albuquerque 2001

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