Masterton District Council (MDC) has closed Henley Lake for recreational use and issued a health warning after tests showed high concentrations of cyanobacteria (toxic algae).

Toxic algae is found in the majority of lakes and rivers in New Zealand, and can increase to very high numbers during periods of warm temperatures, prolonged periods of sunshine, and low water flow through the lake.

The presence of toxic algae is a regular occurrence at this time of year.

Community Facilities and Activities Manager Andrea Jackson said people should avoid contact with the lake water and keep dogs clear.

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

“Exposure 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.”

While people were welcome to use the green space at the park, they should stay clear of the water’s edge.

“Dogs may also be at risk; keep your dogs out of the water and away from the edge. Anyone who believes their dog may have eaten algae or ingested water should contact their vet immediately,” Ms Jackson said.

Anyone experiencing symptoms after contact with the lake should consult a doctor, who will notify the Public Health Unit.

Masterton District Council monitors cyanobacteria weekly at Henley Lake during summer.

The public will be advised of any other changes in water quality that could represent a health risk.