Thousands of fish died in a Gold Coast lake due to a lack of oxygen in the water, tests have revealed.
Gold Coast City Council announced on Tuesday Griffith University tests of water near Clear Island Lake had shown oxygen starvation was the culprit of the die-off.
Mayor Tom Tate said the best indication was that the small bream and mullet were killed when the water "turned over" causing rising algae to diminish oxygen levels in the water.
"I'm advised cold water sinks during some cool weather periods and the muddy water and surrounds on the bottom of the water body then begin to rise," Cr Tate said.
"Algae rising through the water takes a lot of the oxygen and the fish die."
Council has undertaken its own tests on the water looking at oxygen levels as well as bacteria and other conditions.
Those test results are due back by Friday.
