It’s that time of year when toxic algae is starting to show up again in some Marlborough rivers and streams and Council
is asking people to avoid areas of water where it is present.
Council’s monitoring team has noticed toxic algae is starting to become prolific in parts of the Rai River. In previous
summers, the algae would be present in sections of the Wairau and Omaka rivers. This is likely to happen again this
summer.
The algae form thick brown or black mats on rocks in the river bed. These mats have a velvety appearance and can become
detached from the rocks. They often accumulate along the water’s edge, where they decay releasing a musky odour, which
dogs are attracted to.
Council Environmental Scientist Steffi Henkel said because Council can’t survey all of Marlborough’s extensive stream
and river network for toxic algae it’s impossible to put up warning signs at all affected areas.
“Instead we need the community to be aware of the algae, look for it at the river or stream they visit and choose a
different site if the algae is present,” she said.
“The toxins in the algae can be dangerous for children and dogs. If your dog ingests toxic algae you should take it to
the vet immediately. Symptoms usually occur within 30 minutes and include panting, lethargy, muscular twitching,
paralysis and convulsion.”
“In humans, contact with toxic algae can cause vomiting, diarrhoea and skin irritation,” Ms Henkel said.
You can find out more about toxic algae, including how to identify it, on Council’s website: www.marlborough.govt.nz/recreation/swimming-and-boating/toxic-algae