Heil, C. A.. Department of Botany, University of Queensland, C.Heil@botany.uq.edu.au
O'Donohue, M. A.. Department of Botany, University of Queensland, M.Odonohue@botany.uq.edu.au
Dennison, W. C.. Department of Botany, University of Queensland, W.Dennison@botany.uq.edu.au
Moss, A. Queensland Department of Environment, andrew.moss@env.qld.gov.au

 
THE IMPACT OF A FLOOD EVENT ON AN AUSTRALIAN COASTAL ECOSYSTEM
 
East Australian coastal waters, while generally oligotrophic, are subject to unpredictable episodic flood events which can introduce large amounts of inorganic nutrients and suspended sediments into coastal ecosystems. In May of 1996 Moreton Bay, a shallow (8 m), estuarine embayment in southeastern Queensland, Australia, experienced a one in twenty year flood event. Flood inputs (equivalent to 13% of total Bay volume) were sufficient to breakdown the strong nutrient and turbidity gradients which characterise Moreton Bay under non-flood conditions. During the two week flood event, approximately one million tonnes of suspended sediments, 2250 tonnes of nitrogen (N) and 270 tonnes of phosphorus (P) were delivered to the Bay. These nutrient loads represented 110% and 36% of annual average point-source N and P contributions to the Bay. Flood effects upon the marine plant biota of Moreton Bay (ie. a Bay-wide phytoplankton bloom, reduction in seagrass depth range, increased macroalgal nutrient content and saturation of phytoplankton responses to nutrient additions) were short-term; pre-flood gradients in biotic and abiotic indicators of water quality were re-established four months after the flood. This rapid re-establishment of pre-flood conditions suggests that marine plants within subtropical estuaries such as Moreton Bay are resilient to the impacts of single pulsed flood events.
 
Day: Thursday, Feb. 4
Time: 02:00 - 02:15pm
Location: Eldorado Hotel
 
Code: SS52TH0200E