New Zealand Journal of Marine and Freshwater Research abstracts

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Insights into zooplankton-cyanobacteria interactions derived from enclosure studies

CAROLYN W. BURNS

Department of Zoology University of Otago Dunedin, New Zealand

Abstract Few workers have used enclosures specifically to study interactions between zoo-plankton and cyanobacteria. Differences among studies in enclosure size, nutrient level, plankton abundance and species composition, presence or absence of fish, and length of experiments make generalisations difficult. Zooplankton had no direct effect on the growth of ungrazed cyanobacteria (Anabaena flos-aquae, Aphanizomenon flos-aquae, large Microcystis colonies) in short-term (<5 days) and long-term (> 1 month) enclosure studies. When large cyanobacteria were abundant, some Daphnia spp. snowed reduced reproduction and development. When large grazers were abundant they suppressed the growth of edible, colonial cyanobacteria {Aphanizomenon elenkinii, small Microcystis colonies). By altering the ambient light and nutrient environment, large zooplankton may suppress cyanobacteria; evidence for the importance of grazers in promoting cyanobacterial dominance by removing competing phytoplankton species is equivocal. Zooplankton may suppress nitrogen fixation by cyanobacteria through ammonia excretion and may promote a change in dominance from diatoms to cyanobacteria through recycling phosphorus but not silicon.

Keywords blue-green algae; cyanobacteria; enclosures; grazing; interactions; nutrient cycling; species composition; zooplankton

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 477-482 0028-8330/87/2103-0477$2.50/0 © Crown copyright 1987 Received 19 February 1987; accepted 7 April 1987

PDF file of entire paper: medium quality (528K); (scanned from paper original: notes about this process)

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