Lessons learnt from the 2016 blue-green algae outbreak

5 August 2016

You feel feverish… a headache arrives… then a runny nose and all of sudden you’ve got the flu. This is what happened to the River Murray and surrounding areas this year, only it wasn’t the flu — it was blue-green algae.

Blue-green algae is like a flu virus. It takes time to work its way out of the river system, and in fact, for aquatic life in the basin, it is a useful food source.

However it does have damaging effects on the community’s water quality, so there need to be strategies around how we minimise mass outbreaks and reduce the social, environmental and economic impacts.

Reflecting on the outbreak earlier this year helps to build our understanding of the way that it occurred and how future events could be mitigated.

Algal blooms. Photo by Arthur Mostead.
Algal blooms. Photo by Arthur Mostead.

This year we saw a new species of blue-green algae rear its head in the River Murray. It had previously been seen in tropical Queensland and other places such as the Mediterranean, but never bloomed in southern Australia.

The reason for this is still unknown, but climate change is thought to be a factor.  

What we do know are the circumstances that led to outbreak. Blue-green algae needs nutrients, plenty of sunlight, high temperatures, little rainfall and still water.

This year, in the Murray and surrounding areas, we saw all of these conditions. From the beginning of February, when the outbreak began, until May there was very little rainfall and the water temperature in the Murray was around 24°C, conditions which are optimal for algal blooms.

Meanwhile daily temperatures near the Hume Dam were up to 3.5°C above the historical monthly average. At the same time, solar irradiation was also higher than long-term average.

Together, these conditions resulted in the algal bloom along the Murray system and in the Goulburn valley.

Once a blue-green algal bloom forms, very little can be done to stop it. The scale of this year’s events meant that additional flows, were they available, would have been unlikely to significantly reduce the extent of the blooms. Instead the situation had to be managed.

Management of the outbreak was done by local authorities, with help of the MDBA and state governments. This involved signposting emergency meetings, monitoring local algae levels and keeping communities up to date. It was a matter of waiting for the cooler weather, rain and strong winds. Once they arrived, the blue-green algae dissipated.

To avoid this kind of impact on communities in the future, the MDBA is investigating whether the intensity and frequency of outbreaks could be reduced by developing early detection systems combined with targeted flows. We’ll keep you posted. 

*Note – Red alerts for blue-green algae persist at a few locations. See Goulburn-Murray Water and the NSW Office of Water for more information.

Algal blooms on Lodden river near Middle Lake. Photo by Arthur Mostead.
Algal blooms on Lodden river near Middle Lake. Photo by Arthur Mostead.

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