New Zealand Journal of Marine and Freshwater Research abstracts

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Field studies on zooplankton-cyanobacteria interactions

JAMES F. HANEY

Department of Zoology University of New Hampshire Durham, New Hampshire 03824 U.S.A.

Abstract Correlative field evidence suggests that large grazers such as Daphnia pulex promote the growth of colonial cyanobacteria by selectively eating competitive phytoplankton. This is supported by experimental evidence that (1) in eutrophic lakes dominated by cyanobacteria grazing by zooplank-ton on small particles is often > 100% day¹, and (2) colonial cyanobacteria are generally not grazed as rapidly as smaller phytoplankton. Cyanobacteria generally have deleterious effects on grazing zooplankton. Filamentous cyanobacteria such as Anabaena and Oscillatoria can inhibit filtering by cladocerans, reducing growth and reproduction. Detrimental effects on zooplankton via nutritional deficiencies and toxins of cyanobacteria have been demonstrated in the laboratory but not in the field. Grazing on colonial cyanobacteria by zooplankton appears to be an important trophic link in tropical lakes. Generally, calanoid copepods seem best adapted to utilising large cyanobacteria. The generalisation that, with increasing eutrophication, zooplankton communities tend to shift from a dominance of calanoid copepods to cladocerans, does not apply to lakes in New Zealand.

Keywords algal blooms; Anabaena; Aphanizo-menon; blue-green algae; cladocerans; copepods; cyanobacteria; Daphnia; filter-feeding; grazing; herbivores; Microcystis; toxins; zooplankton

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 467-475 Received 19 February 1987; accepted 7 April 1987

PDF file of entire paper: medium quality (771K); (scanned from paper original: notes about this process)

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