Toxic algae blooms in Waipoua and Hutt rivers - dogs and people to avoid contact with water

Red alert level warnings are in place for the Waipoua River at Columbo Road in Masterton and the Hutt River at Silverstream Bridge. 

Greater Wellington is urging people not to swim in these river areas, or let their dogs enter the water. Dog walkers should also avoid the river’s edge where significant amounts of toxic algae have accumulated.  

Greater Wellington manager of knowledge and insights Dr Evan Harrison says toxic algae is a neurotoxin that acts like snake venom, which can be harmful to humans and lethal for dogs if ingested. 

“We strongly advise people to avoid contact with water, and to keep all dogs and children away from the river’s edge,” Dr Harrison says.  

“Even a small amount of toxic algae, the size of a 50-cent piece, can be enough to kill a dog.” 

Dog owners who think their animals have swallowed toxic algae, or shows signs of lethargy, muscle tremors, fast breathing, paralysis or convulsions, should go to the nearest vet immediately.  

People who have been in contact with toxic algae and are feeling unwell, should see a doctor or ring Healthline on 0800 611 116.

The community is advised to check the LAWA website for toxic algae warnings and alerts before visiting rivers in the Wellington region this summer. 

“Toxic algal blooms form naturally when river temperatures increase,” says Dr Harrison. “It’s important everyone knows how to spot toxic algae to keep their pets and whānau safe.”  

Toxic algae grows on rocks in the riverbed and forms leathery, dark green or black mats, which can break off and accumulate at the river’s edge. 

Greater Wellington is currently monitoring popular river swimming spots for toxic algae on a weekly basis. 

Learn more about toxic algae

Check for toxic algae alerts in the Wellington region