Freshwater Toxic Algae

Greater Wellington Region

Did you know that toxic algae in rivers is especially harmful to dogs. As the weather gets warmer, toxic algae can cause some of our waterways to become unsafe to swim in. It’s normal to expect some degree of blue green algae in the Waikanae River (from SH1 to the river mouth) and in the Ōtaki River during warmer months and sometimes even during mild winters. 

  • There’s always a risk of harm to your dog if you let it swim or scavenge in the lower reaches of our rivers and streams, because algal blooms and dislodged algal mats can occur along the river at any time.
  • If toxic algae reaches harmful levels for humans in any of the Kapiti Coast District monitored recreational water sites, Kapiti Coast District Council will release public notifications to let everyone know.     

Dogs are most at risk, as they like the musty smell of algae mats that wash up on the river’s edge. A small amount, the size of a 50 cent piece, can be enough to kill a dog.We know how much dogs love the water, so it’s always best to check for alerts before you take them to play near a river. Keep an eye out for warnings, and check for alerts online at

For more information on toxic algae, see Greater Wellington’s toxic-algae-faqs


Toxic Algae blooms have been detected in Waikanae river at both State Highway One and James Cooke Park this week, meaning extra caution is needed when exercising dogs in these areas.Toxic Algae is toxic to humans and can be deadly for dogs if eaten.The best thing you can do when Toxic Algae is present is keep your dog on a lead and stay out of the water. Algae is quickly dispersed and deactivated by salt water, so it’s safer to walk your dog at the beach instead of at rivers during the summer.

Infomation supplied by KCDC and GWRC