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Dog owners - look out for black mat algae

Sam at the river 002

Dog owners are urged to keep an eye out for black mat algae when walking dogs along rivers with stony beds, especially the Tukituki and Waipawa rivers. 

Black mat algae, called Phormidium, occurs naturally in many Hawke’s Bay’s rivers and is not linked to poor water quality. However, it has the potential to cause serious illness in people and dogs as it can release toxins into the water.  

“At the moment there’s an added risk to dogs because river levels are low. Dogs are attracted to the musty odor of the exposed or detached toxic mats that have washed ashore and dried, and may eat them,” says Hawke’s Bay Regional Council Water Quality and Ecology Scientist Dr Gary Rushworth. 

“It’s important that dog owners are aware of what black mat algae looks like. It can also be brown, or grey when it has dried. Always treat the black growth on rocks in the water and the drying mats as toxic. Swim or walk your dog somewhere else, he says. 

Hawke’s Bay District Health Board has posted warning signs where there is known to be a high risk. Exposed or detached black mats are currently common throughout the Tukituki and Waipawa rivers.It is recommended dog owners avoid these locations, and exercise caution at other stony rivers.  

For more information visit  or see our dog owners guide  

28 May 2019

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