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Masterton District Council has closed Henley Lake for recreational purposes and issued a health warning after tests show concentrations of cyanobacteria (toxic algae) to be at high levels.

Toxic algae (cyanobacteria) is found in the majority of lakes and rivers in New Zealand. Under certain conditions, including warm temperatures, prolonged periods of sunshine and low water flow through the lake, the algae can proliferate to very high numbers.

Masterton District Council Regulatory Services Manager, Steven May said the most recent testing at Henley Lake has confirmed very high concentrations of cyanobacteria (toxic algae).

“People should avoid all contact with water in Henley Lake – in particular children, pregnant women and the elderly,” Mr May said.

The greenspace around the lake if fine to use, but people should stick to the paths and stay away from the water’s edge,” he said.

Cyanobacteria is also a high risk for dogs, which should be kept out of the water and away from the lake’s edge.

“Anyone who believes their dog may have eaten algae or ingested water should contact their vet immediately,” Mr May said.

Cyanobacteria produce toxins that are harmful to humans and animals if swallowed or through contact with skin through activities such as during swimming or rowing.

Exposure to cyanobacteria may cause symptoms such as skin rashes, nausea, tummy upset, and tingling or numbness around the mouth or tips of fingers.  Pregnant women, children and the elderly are more likely to be affected.  If you experience health symptoms after contact with the Lake, consult a doctor.  Your doctor will notify the Public Health Unit.

Masterton District Council monitors cyanobacteria weekly at Henley Lake during the summer, with the public being advised of any other changes in water quality that could represent a health risk.

Current information on toxic algae levels at Henley Lake can be found on the front page of the Masterton District Council website alongside Greater Wellington Regional Council information on where it’s safe to swim at sites across the region.