Photo: ORC

The Otago Regional Council (ORC) is warning people and their dogs to stay away from the water of Tomahawk Lagoon in Dunedin, after potentially poisonous blue-green algae was found.

The ORC collected a sample from the water yesterday after it was alerted to the presence of the algae bloom by a citizen scientist who was working there.

There were signs in place near the beach access to warn the public of the risks associated with the algae, which was located mainly at the bottom lagoon and contained a high level of cyanobacteria.

"The lagoon discharges into the stream running onto the beach, so beachgoers should take care in this area."

Cyanobacteria can produce toxins that are harmful to humans and animals if swallowed or through contact with skin. Exposure to cyanobacteria may cause symptoms such as skin rashes, nausea, tummy upset, and tingling and numbness around the mouth or tips of fingers.

"If the water is green or has floating bright green or blue scums, all contact should be avoided."

Anyone experiencing health symptoms after contact with contaminated water should visit their doctor. Public Health South is available on (03) 4769800 to provide health professionals with information about those symptoms.

Cyanobacteria occur naturally but can increase rapidly during summer months.

The Otago Regional Council said it would continue to monitor the situation and update the public as the algae bloomk changes.