Mon July 16, 2012 7:01pm
LARGE numbers of dead fish in northern NSW rivers following floods have prompted scientists to investigate.
Southern Cross University is looking at the Richmond River and the chemicals that entered it during floods.
They cause what is termed "blackwaters" to drain from coastal wetlands into the rivers, killing fish and other river life.
At Ballina there were hundreds of dead fish, yabbies and even bull sharks after the 2010 floods, and less serious events since then.
Associate Professor Andrew Rose says three key factors are being investigated.
Firstly it is believed that different types of soil have chemicals that can cause this consumption of oxygen.
Secondly, land use with regards to cropping, grazing and protected land practices can have adverse effects on the river system.
Finally, types of vegetation can break down in flooding providing food for bacteria that contributes to this oxygen consumption.
Prof Rose hopes the information collected will allow the development of a model to predict the effects of flooding and the chemicals that come with it.
"Hopefully it will be able to predict the outcomes of situations like if it rains this much, what will this do?" he said.
"Will we get enough rain to cause the release of these chemicals into the river?
"It could also allow us to deal with hypothetical questions like if we changed the land use of a particular patch of land, how would this affect the river?"
The study is being done in partnership with Richmond River County Council.