Dog owners need to keep their pets out of the water in Butchers Dam, near Alexadra, as toxic algae has been found there.

The Otago Regional Council (ORC) advised people yesterday (Wednesday November 15) to stay out of the dam and keep dogs well away from the water and dam edge.

Cyanobacteria, a blue-green algae, can potentially produce toxins harmful to humans and pets if swallowed, or through contact with skin, ORC water quality scientist Rachel Ozanne said.

The warning to keep clear of the dam will remain in place until weekly testing shows that the cyanobacteria is no longer a health risk.

Algae often begin blooming at this time of year from a combination of rising water temperatures, the increase of sunlight hours and nutrients in the waterways.

A member of the public alerted ORC that an unusual algae was present at Butchers Dam, and subsequent testing identified it was cyanobacteria. 

The algae bloom from above at Butchers Dam. PHOTO: ORC

“What’s happened at Butchers Dam is an indication that other lakes are likely to experience algae blooms too and the public should inform themselves of what to look for,” Rachel said.

Cyanobacterial blooms are generally green in colour and can give lakes a “pea soup” appearance; they can also persist outside of the summer months. 

“They can also form visible green to red films or scums on the water’s surface, especially at the water’s edge.”

There have been instances in the past where dogs, birds, cattle and other wildlife have died from exposure to cyanobacteria.

Symptoms can include lethargy, tremors, paralysis, foaming at the mouth or vomiting.

“Affected animals should be taken to a vet immediately,” Rachel said.

Anyone who suspects they are experiencing a reaction due to contact with toxic algae should seek medical attention.

If you spot green algae in lakes, or dark mats in streams and rivers, contact the ORC 24/7 pollution hotline - 0800 800 033.

For more information on potentially toxic algae, see LAWA’s factsheet: Click here