FEWER toxic algae blooms at Lake Burley Griffin are the result of weather conditions rather than adequate water and nutrient pollution prevention, according to the professor of water science at the University of Canberra.
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Dr Ross Thompson said no claims about improving water quality could be made until there had been successive years without lake closures.
''We haven't dealt with the management issues of the lake. Last year was simply a time where conditions didn't lend themselves to blooms,'' he said. ''We may have individual years without blooms, but until we get a series of years in a row without blooms we can't confidently say we have dealt with water quality issues.''
The most recent water quality tests published on November 4 found that bacteria and algae levels were low. The highest readings of enterococci were found at Weston Park East and the highest level of blue-green algae cells was found at the east basin, 4348 cells per mL.
But National Capital Authority acting chief executive Andrew Smith said one of the best summers in terms of lake closures showed things were on the right track. The authority is responsible for the condition of the lake and is two years into a three-year trial that aims to improve the lake's water quality. Three solar-powered water circulators, costing $350,000 in the first year, were installed in 2011 to mix low oxygen water that is more acidic than the rest of the water column and makes phosphate available to blue-green algae.
''We haven't had a conclusive result one way or the other on that. It's not making water quality worse or making it better,'' Mr Smith said. He said the NCA had worked to improve water quality through capital works including fencing cattle away from the lake and releasing more than 40,000 fingerlings.