Title: The role of zooplankton in cyanobacteria bloom development in Australian reservoirs
Supervisors: Dr Martina Doblin, UTS and Assoc Prof Peter Ralph, UTS
PhD conferred: 2013
Cyanobacteria (blue-green algae) are becoming increasingly abundant in freshwater ecosystems worldwide¹. They are favoured in nutrient-enriched, stratified environments and when toxic, can be fatal to humans and animals. Cyanobacteria are also prevalent in Australia’s subtropical reservoirs²‚³.
Two main approaches have been mooted for preventing or controlling cyanobacterial blooms: the bottom-up approach restricts the supply of essential nutrients for algal growth, and the top-down approach restructures the food web to maximize consumption of cyanobacteria by herbivorous zooplankton. The relative importance of top-down grazing processes for controlling cyanobacterial growth has been debated (4), as some zooplankton are selective consumers and avoid ingesting cyanobacteria. Furthermore, under nutrient-limited conditions, zooplankton may have positive impact on cyanobacterial growth by regenerating nutrients through consumption of other; more palatable algae(5).
This project aims to resolve the role of zooplankton in the development of cyanobacterial blooms by testing these alternative hypotheses simultaneously. The project outcome will be a process-based model to predict the likelihood of cyanobacterial bloom formation under different environmental conditions, significantly improving the management capacity for intervention and mitigation, with significant water treatment savings.
The objectives of this project are to:
1. Estimate nutrient release rates by zooplankton feeding on phytoplankton communities in freshwater reservoirs with different nutrient enrichment (bottom up), and assess the magnitude of zooplankton-derived nutrients compared to other nutrient sources
2. Determine zooplankton secondary production, trophic position and grazing rate (top-down) on freshwater phytoplankton communities with different cyanobacterial abundances.
3. Build a process-based nutrient-phytoplankton-zooplankton model using understanding from aims 1 and 2 to provide a strategic tool for water resource protection and management.
1. Paerl, H.W. (1988) Limnol. Oceanogr. 33: 823-847
2. Burford, M. and O’Donohue, M. (2006) Freshwater Biology 51: 973-982
3. Burford, M., Johnston, S.A., Cook, A.J., Packer, T.V., Taylor, B.M., Townsley, E.R. (2007) Water Research 41: 4204-4114
4. Boon, P.I., Bunn, S.E., Green, J.D., Shiel, R.A. (1994) Australian Journal of Marine and Freshwater Research 45(5): 875-887
5. Havens, K., East, T. And Beaver, J. (1996) Freshwater Biology 36: 579-597.