Ford, P. W. CSIRO Land and Water, Phillip.Ford@cbr.clw.csiro.au
Bormans, M. CSIRO Land and Water, Myriam.Bormans@cbr.clw.csiro.au

 
NUTRIENT AND CYANOBACTERIAL DYNAMICS IN A STRATIFIED TROPICAL BARRAGE
 
The Fitzroy Barrage ( capacity 60,000ML ) is a 50 km long impoundment in tropical Australia subject to blooms of toxic cyanobacteria. Infrequent monsoonal rains fill the barrage with highly turbid water. The initially well-mixed storage gradually stratifies and the water column slowly clears (in approx. 100 days) by settling of the fine particles ( 80% < 1 um ). Nutrients ( especially ammonia ) are scavenged by the settling particles. Only small algal species with high specific uptake rates can grow then. They use nutrients diffusing from the hypolimnion supplemented by episodic pulses from intermittent mixed layer deepening. Benthic fluxes are sufficient to keep hypolimnetic nutrient concentrations in balance. Observations at the 2 ends of the barrage differ temporally reflecting local topography and meteorology. We report on the interacting physical, chemical, and biological processes which ultimately create conditions favourable to cyanobacterial growth.
 
Day: Friday, Feb. 5
Time: 11:45 - 12:00pm
Location: Eldorado Hotel
 
Code: SS42FR1145E