The Otago Regional Council today advised that the algae Phormidium has been confirmed in the waterway.
The discovery has prompted the ORC to warn dog owners to be vigilant when exercising their pets alongside Otago’s rivers and streams, and to stop them from eating any scavenged material.
The warning comes as warm weather post-Christmas causes river levels in Otago to drop.
Phormidium occurs naturally in waterways, but can become a problem in summer when the algae can form thick mats on river beds, especially during low flows.
Otago Regional Council science manager Dr Dean Olsen said high river flows before Christmas kept the region’s rivers relatively free of Phormidium.
However, warmer temperatures since Christmas and the resulting stable flows meant Phormidium has the opportunity to flourish, certainly in the Cardrona, and possibly in other historic trouble spots such as the Lindis, Manuherikia, Taieri (Silverstream), Kakanui, and Waianakarua rivers.
“It is important that people using waterways are aware of the risks associated with its possible presence, and are alert to this wherever they are in Otago,” Dr Olsen said.
There have been cases in New Zealand of dog deaths associated with toxic algae where dogs have eaten the mats formed by Phormidium, having been attracted by their deep earthy odour.
“If the bed of a river is covered in thick dark brown or black mats that have a velvety texture and a musty smell, it is wise to be cautious and avoid that river site,” Dr Olsen said.
Pets should be taken to a vet immediately if they show signs of illness after coming into contact with algal mats. The greatest risk is to dogs, which are more likely to consume the mats in the water.
“The most common signs that a dog might have consumed toxic algal material are lethargy, muscle tremors, fast breathing, salivation, twitching, paralysis and uncontrolled shaking, convulsions, or frothing at the mouth soon after being in the water.”
Anyone concerned their pet may have consumed toxic algae should contact their vet immediately, he said.
