Bay of Plenty Regional Council is treating Okawa Bay on Lake Rotoiti with a product to prevent potentially toxic blue-green algae blooming on the lake.

The council's lake operations manager Andy Bruere says the council was alerted to a risk of the harmful algae forming during its routine monitoring, and from its environmental advisors, including Waikato University professor David Hamilton.

File picture.

The aim of the treatment – with a modified zeolite product called Aqual P – is to avert the need for health warnings on the lake if a predicted bloom occurs.

The presence of blue-green algae can close the lake to swimmers and boaties.

'The regional council has experience with the application of Aqual P on Lake Okaro and tests have shown it is safe to use in the natural environment,” says Andy.

'It was applied to that lake in 2007 and 2009 to deal with eutrophication problems (where nutrients enter the lake and deplete oxygen).

'The product will rapidly settle and flocculate algae, and lock up phosphorus in the water column.”

Andy says the product is not expected to cause any ill health effects for animals.

Monitoring after applications at Lake Okaro has identified no harmful effects from the use of this product.

'This option is being trialled at Okawa Bay because the algae is potentially toxic and the location is conducive to the technique.

'We have needed to move quickly due to the potential for algae numbers to increase rapidly under current weather conditions.

'We plan to apply a slurry to Okawa Bay which will lock up phosphorous and drop the algae to the bottom of the lake.”

Council staff met with Okawa Bay residents on Sunday to explain the process and are working with trustees of Maori trust land being used as a base for the operation.

The slurry will be applied from a helicopter and should be completed within two hours.

A comprehensive monitoring programme has been designed to determine the success of the application and ensure any effects are identified.