Environment Southland monitoring has shown a high abundance of benthic cyanobacteria (blue-green algae) at two sites.

People and animals, in particular dogs, should avoid contact with reaches of the Hamilton Burn around Affleck Road and the Upukerora River around the Te Anau-Milford Road until health warnings are removed.

Public Health South medical officer of health Dr Derek Bell says cyanobacteria produce toxins that are harmful to people and animals if swallowed or through contact with skin. Boiling water does not remove toxins and drinking of the water should be avoided at all times.

“Exposure to cyanobacteria may cause symptoms such as skin rashes, nausea, tummy upset and tingling and numbness around the mouth or tips of fingers,” he says.

Cyanobacteria occur naturally but can increase rapidly during warmer periods of the year. Benthic cyanobacteria usually occur as dark brown/black mats which grow attached to rocks in the river or accumulate on the surface in shallow, slow-flowing areas. They often have a strong, musty smell.

If you experience health symptoms after contact with contaminated water, visit a doctor immediately. Animals that consume cyanobacteria should be taken to a vet immediately.

Environment Southland monitors cyanobacteria monthly at a number of sites across Southland and the public will be advised of any changes in water quality that are of public health significance. For further information, visit Environment Southland’s website.