The public is being urged to be on the lookout for potentially toxic algae, with a dry summer in Otago creating a climate for it to flourish in rivers.
Dog owners are advised to keep their animals away from water where toxic algae may be present. Photo: RNZ
The Otago Regional Council has issued a warning for people - dog owners in particular - to be on the lookout for the naturally-occurring algae Phormidium, also called blue-green algae.
It has been spotted in many Otago waterways this summer, including the Waianakarua River in North Otago, the Silver Stream near Mosgiel, and the Manuherikia in Central Otago.
The council said where the algae was noticeable, people should assume the water is unsafe for their animals to swim in.
