What’s watery, green and stinks? The answer: Lake Tuggeranong. The pungent smell and bright green hue has scientists and researchers puzzled as to why the lake is presenting such an overwhelming feast for the senses.
For Southside locals, that eye-stinging smell wafting through the town centre is emanating from the lake and its massive algae bloom, which has been closed to primary contact activities – such as swimming and bathing – since December last year.
So what is causing this extreme bloom? University of Canberra water ecologist Ross Thompson is currently doing studies on the lake’s water quality, hoping to find an answer – and a way to treat it.
He said it was the worst algae case he had seen in the nation’s capital and as the nights start to get cooler, he believes the algae will only get worse.
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“This algae case in Tuggeranong is now worse than a lot of the pictures that we see in a lot of textbooks showing what a blue-green algae bloom looks like,” Mr Thompson shared.
“I have taken a lot of photos and shown students that this is what blue-green algae look like. It has even got the perfect blue-green colour.”
Put simply in layman’s terms, the combination of warm days followed by cold nights is what causes blue-green algae in the lake.
According to Mr Thompson, the warmer top of the lake and the colder bottom keep the nutrients separate thanks to the warm summer months, but as the warmer top of the lake starts to cool, the water mixes, bringing the nutrients and the algae.
“Everyone will have noticed that we have had a prolonged warm spell where the days have been much warmer then we would have expected for this time of year,” he shared with Region Media.
“Now we are getting cold nights as well so when we have prolonged warm conditions, all of the nutrients tittle out of the warm water and plop into the cold water at the bottom.
“When you have a cold night, the cold water and the warm water mix together, causing the blooming of blue-green algae.”
Mr Thompson said once the air temperatures start to drop in the coming month, the levels of algae will start to collapse but until then, he and his team of researchers will find out how to treat a bloom of this nature after it has started.
“Normally, if want to stop a big bloom like this, the reality is to go out and intervene early but the work that we have been doing at the moment is trying to treat the bloom after it has started,” he said.
Mr Thompson is also hoping to figure out why Lake Tuggeranong has such an excess nutrient problem.
“There is a high-nutrient load to the lake and we are still trying to get a handle on where that is coming from. We are running a program this year where we have been looking at the inflows to the lake, which has shown large amounts of phosphorous and nitrogen, loads which we can’t explain with a simple explanation.
“Our ongoing work is going back up into the catchment and trying to work out what the sources are for the nutrients.”
Anyone concerned about possible symptoms of blue-green algae exposure following water exposure should contact their GP.
For more information on blue-green algae and alert levels, click here or contact the Environment Protection Authority through Access Canberra on 13 22 81.