Environment Southland’s latest monitoring has found high levels of potentially toxic algae in the Waihopai River at the dam upstream of Queens Dr in Invercargill.
Environment Southland senior scientist Katie Blakemore said water users should be vigilant and avoid contact with the algae.
"This is a particularly popular spot for dog walkers and many people walk their dogs off the lead in the area. Pet owners should take extra care in this area, and all the way along the Waihopai River as ingesting just a small amount can be toxic to dogs," she said.
Most algae are harmless. However, some species can produce toxins and rapidly bloom to high levels. Toxic algae is commonly identified in waterways as a dark green/brown slime on rocks, or dark brown/black mats at the water’s edge.
Swimming there should also be avoided.
"These algae can produce toxins that are harmful to people and animals if swallowed, or through contact with skin. People should keep dogs on a lead and children away from affected areas. Be mindful of the potential health risks, until health warnings are removed."
Anyone showing symptoms after contact with contaminated water, should see a doctor immediately. If people were concerned animals had consumed toxic algae or contaminated water, they should be taken to a vet immediately.
Similar algae growth might occur in other waterways in the area.
There are already toxic algae warnings in place for the Waihopai River at Kennington and the Waiau River upstream of Excelsior Creek.
