Suspected algal bloom at Quarry Lake

February 21, 2006

North Shore City Council is advising people not to use the Quarry Lake next to Lake Pupuke because of a suspected algal bloom problem.

Public health warning signs have been erected around the lake area after the council's Swimsafe helicopter sampler noticed discolouration of the water and testing revealed high levels of blue-green algae.

"Blue-green algae blooms are a naturally occurring phenomena but can be toxic to humans, so we are advising the public not to swim while warning signs are in place," says North Shore City's pollution prevention coordinator, Natalie Managh.

"Algal concentrations will be retested weekly until they are within safe levels when the signs will be taken down," she says.

Although it has not been confirmed that this particular algal bloom is toxic, about 20 percent of blue-green algae blooms are toxic and can cause numerous health problems including skin irritation, fever, fatigue, vomiting, diarrhoea, abdominal pain, cramping and nausea. Toxins can also affect the liver and nervous system.

Algal blooms occur naturally and there is no way of preventing or getting rid of them. They can be triggered by short bursts of warm weather, low rainfall and high nutrient levels. There was a similar problem at Quarry Lake last year, which lasted for about a month before clearing.

"There is no sign the bloom has affected Lake Pupuke and testing shows it to be safe at present," says Ms Managh.

Samples from recreational water areas are taken weekly over summer as part of the Safeswim Programme.

People can contact North Shore City Council's Actionline on 486 8600 for more information or ring 0800SAFESWIM for general information regarding bathing water quality at our city's beaches and lakes. Safeswim weekly results are also posted on the council's website at www.northshorecity.govt.nz

ENDS

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