Council Warns Dog Owners To Look Out For Poisonous Algae In Waterways

Kāpiti Coast District Council is advising dog-owners to keep an eye out for toxic algae in the district’s waterways as the temperature rises. This includes lagoons in parks and reserves as well as rivers and streams.

Toxic algae mat washed up on river’s edge

There are now dangerous levels in Waipoua River in the Wairarapa and elevated levels in Te Awa Kairangi (Hutt River) — and the Kāpiti Counci is worried about algae dangers here.

Summer dangers

Kāpiti Coast Environmental Manager Jacquie Muir says seasonal changes occurring now impact on algae levels and it’s likely that locals will soon see toxic algae in some parts of Kāpiti.

“We’re noticing the water levels slowly dropping and temperatures rising. So it is possible cyanobacteria, an algae which is toxic to humans and deadly for dogs, will appear. We’re increasing signage at swimming sites and taking this opportunity to remind people to be aware of the risks,” says Ms Muir.

The Council will maintain its seasonal monitoring program at swimming sites, in partnership with Greater Wellington Regional Council. This happens weekly during the summer months.

Test results from popular river, lagoon and beach locations are available on the Council’s website.

Check for toxic algae

Signage at popular swimming sites is increasing to remind people to check for signs of toxic algae.

Algae at water’s edge

Toxic algae (cyanobacteria) generally form brown or black mats that grow on rocks in the river bed. Mats that come loose from the river bed can wash up on the river bank or form floating ‘rafts’ in shallow areas.

When exposed, the mats may dry out and turn a light brown or white colour and may also produce a strong musty odour. Cyanobacteria differ from harmless bright green algae, which often form long filaments.

It is important to keep an eye on babies and toddlers who may put objects in their mouths. Seek emergency medical attention immediately if anyone in your group swallows toxic algae.

Caution should also be taken when exercising dogs by rivers as they are strongly attracted to the musty smell of drying mats and will eat them where they can, which could be fatal.

The 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.

Given the rapid growth of toxic algae and its potential change in coverage between weekly monitoring points people are also urged to know what it looks like.

“If you suspect toxic algae might be present then keep your dogs out of the water and let us know,” says Ms Muir.

Greater Wellington Regional Council has more information about toxic algae at

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