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3 September 1998 |
Ref 98/206 |
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This summer, CSIRO scientists are planning to go to war against one of the most widespread threats to the health of the environment and community - toxic blue green algae.
With the return of the warm weather, algal blooms spread their insidious poison in many of Australia's city water supplies, rivers, irrigation and farm dams - but six years' intensive research is yielding an armoury of tactics to control the plague.
If the new methods work in the field this summer, it will make Australia a world leader in the race to develop broad control strategies against blue-green algae under a wide range of conditions, says CSIRO Land & Water program leader Dr Richard Davis.
"Up till now blue-green algae have posed constant problems in the warm months for urban water storages in Brisbane and Adelaide as well as regional cities. It has cost the community millions of dollars to keep the water supply clean," he says.
"We have large irrigation supply dams and weir pools in our major rivers that turn blue-green every summer, and there is a risk of water containing algal toxins going onto crops and even into the food chain.
"Farm dams are increasingly affected, and this poses problems for the livestock industries, especially dairying."
Blue-green algae are also a periodic threat to the health of urban lakes and rivers in summer, and to the thousands of citizens and their children who use them for recreation.
Dr Davis says that over the past six years a team of CSIRO water scientists has laboured to build up an understanding of the complex chain of events that leads to an algal bloom, and the aftermath of toxins released into the water.
"We now believe we have a toolkit of methods that can tackle the problem of algal blooms in a wide range of circumstances, and we are keen to put them to work in real life settings to see if we can fix the problem," he says.
The methods start with the sediments at the bottom of the water body: CSIRO scientists and the Western Australian Water and Rivers Commission have developed modified clays that can be spread to prevent the leaking of nutrients that feed the algae.
The ecology of the water can be altered, Dr Davis says. For example, one reason for algal blooms is that small fish eat the tiny creatures which normally keep the blooms in check. Introducing large predatory fish can reduce numbers of small fish, and so allow the tiny water creatures to survive and eat down the algae.
The balance of nutrients in the water can be shifted to favour diatoms and other microscopic life in preference to blue-green algae. Water weeds can be used to soak up the nutrients which blue-green algae depend on.
"There is also quite a lot we can do about catchment management to prevent fresh phosphorus from entering the water body and triggering algal blooms," he says.
CSIRO has developed a range of tools for tracing the sources of nutrients in a catchment, so they can be pinpointed and checked. These can show whether the blooms are feeding on nutrients from fertiliser runoff, sewage effluent, erosion, city stormwater or some other cause.
"We now have ways to find out where all the nutrients entering a water body are coming from, so we can nail them one by one," he explains.
"If, for instance, the nutrients are coming in on clay particles in eroded soil, we can put in place erosion control measures that suit the particular circumstances - tree and soil types, cause of the erosion and so on."
Dr Davis says that Australia has an unprecedented opportunity to package this array of techniques for preventing algal blooms.
"Many countries round the world are experiencing similar problems in their lakes, rivers and drinking water supplies, so there are large export opportunities for Australian companies specialising in ways to prevent outbreaks of toxic algae.
"CSIRO Land and Water is now keen to test out kit of
tools in as many situations as possible, and we would like to
hear from local authorities, landholders and water managers about
situations in which we can try them out," Dr Davis says.
More information from:
- Dr Richard Davis, CSIRO Land & Water 02 6246
5706
Margaret Bryant, CSIRO Land & Water 08 9333 6215
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