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Phytoplankton blooms in the Huon Estuary, Tasmania: top-down or bottom-up control?


Thompson, PA and Bonham, PI and Swadling, KM, Phytoplankton blooms in the Huon Estuary, Tasmania: top-down or bottom-up control?, Journal of Plankton Research, 30, (7) pp. 735-753. ISSN 0142-7873 (2008) [Refereed Article]

DOI: doi:10.1093/plankt/fbn044


The roles of "top-down" and "bottom-up" factors were investigated in terms of their influence on the diatom and dinoflagellate abundances in the microtidal, salt wedge Huon Estuary, Tasmania, Australia. Long-term (1996-2005) changes in Chl a, the peridinin:Chl a ratio and the abundance of autotrophic dinoflagellates were observed to coincide with the warming of regional surface waters. There were significant seasonal differences in pigment-specific net growth rates for Chl a, peridinin and fucoxanthin. Diatoms dominated the spring bloom when species such as Skeletonema costatum had the highest net growth rates and fucoxanthin-specific gross growth rates were ∼0.9 day-1. During late summer, the peridinin-specific grazing mortality was significantly less than the fucoxanthin-specific grazing mortality and dinoflagellates increased their dominance of the phytoplankton community. This late summer relaxation of grazing pressure on dinoflagellates was associated with a decline in the overall abundance of microheterotroph (MH) grazers and a peak in the abundance, biomass and estimated grazing rates of mesozooplankton. We suggest the composition of the autumn phytoplankton community was dependent upon a trophic cascade where mesozooplankton, such as Noctiluca scintillans, preyed upon MHs and reduced their grazing upon some species of dinoflagellates.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Coastal or estuarine biodiversity
UTAS Author:Swadling, KM (Associate Professor Kerrie Swadling)
ID Code:54490
Year Published:2008
Web of Science® Times Cited:33
Deposited By:TAFI - Marine Research Laboratory
Deposited On:2009-02-24
Last Modified:2019-03-31

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