Toxic algae in Waipoua River

  • Published Date 19 Dec 2016

High levels of toxic algae have been found in parts of the Waipoua River, near Masterton, prompting authorities to warn dog owners to keep their dogs on the lead and people to avoid touching or swimming near the algae.

Monitoring of the Waipoua River at Colombo Road by the Greater Wellington Regional Council shows that the amount of black or brown toxic algal mats growing on the river bed has reached dangerous levels and detached mats are starting to wash up on the river's edge.

If ingested, the toxic algae can kill livestock and dogs. Some people can be sensitive to toxic algae and may get a skin rash or irritation from touching it.

"Despite some recent rain, flow in the Waipoua River is dropping and temperatures are warming-up providing ideal conditions for algal growth" says Environmental Scientist Mark Heath.

Masterton District Council has posted toxic algae information signs at key access points along the river.

Monitoring of Wellington waterways and coastal areas is carried out by Greater Wellington Regional Council and local authorities in partnership with Regional Public Health on a weekly basis over the summer months.

Results of the monitoring and any warnings are posted on our website - Is it safe to swim?

Here's information about toxic algae, including a guide of what to look for and what to do if you are worried about possible contact with toxic algae.



Media Contact: 021 914 266 or



Mark Heath

Environmental Scientist

Environmental Management Group

Greater Wellington Regional Council

027 464 6030


Medical Officer of Health

Regional Public Health

04 570 9002

04 570 9007 (after-hours)

Updated October 3, 2023 at 4:49 PM

Get in touch

0800 496 734