Current Conditions in the Wakool River System and the potential for a blackwater event resulting in fish deaths

"February 2009".

Project Number: MDFRC Core Project.

MDFRC item.

00000nam a22000002a 4500 20uu9999 |||||s|||||00| 0|eng d report local Murray-Darling Freshwater Research Centre, 2009. Funding agency: The Murray-Darling Freshwater Research Centre - Pro bono Client: The Murray-Darling Freshwater Research Centre "February 2009". MDFRC project number: MDFRC Core Project MDFRC publication number: MDFRC Technical Report en Current Conditions in the Wakool River System and the potential for a blackwater event resulting in fish deaths MDFRC item. Blackwater events are a natural part of the ecology of lowland river systems. During a flood, carbon compounds are leached from leaf litter laying on the floodplain or dry flood runners/creek channels in much the same way that tea is leached from tea leaves. However, blackwater events can markedly change water quality. Microbes can immediately use about one-third of the carbon leached from the leaf litter. As the microorganisms consume the dissolved carbon they use up oxygen in the water – often at a rate faster than the oxygen can be replenished. Therefore, blackwater plumes often have very low levels of dissolved oxygen. The lack of dissolved oxygen can cause the death of fish and other aquatic animals in the plume. Native fish and other large aquatic organisms require at least 2 mg/L of oxygen in the water to survive, but may begin to suffer at levels below 4-5 mg O2/L (Gerhke, 1988). A number of factors are critical in determining whether or not a blackwater event will result in a fish kill. The two most important factors are water temperature and carbon loading. 6 p. 270000 Biological Sciences asrcfor Blackwater events Edwards-Wakool region Fish kills Colligen Creek Baldwin, Darren S. The Murray-Darling Freshwater Research Centre Whitworth, Kerry The Murray-Darling Freshwater Research Centre full rightsfull rightsfull rights Open Access.