Toxic algae found in Kaiko¯ura river

Swimmers and dog walkers have been urged to avoid the Kahutara River near Kaiko¯ura and the Hutt River in Wellington due to outbreaks of potentially toxic algae.

Blue-green algae (benthic cyanobacteria) was found in the Kahutara River and the presence of toxic algae mats had been consistently rising in the Hutt River at Birchville, Maoribank, Poets Park and Silverstream throughout January.

The health warning comes after the Canterbury District Health Board lifted an algae warning for the Waikirikiri River at Whitecliffs Domain on Wednesday. The warning had been issued on December 21, 2017.

Canterbury medical officer of health Alistair Humphrey said a doctor should be notified immediately if anyone came in contact with algae mats.

‘‘Although the algal bloom in the Kahutara River is only at a moderate level, the phormidium (benthic cyanobacteria) mats are detaching, floating downstream and accumulating in the lagoon, so I would advise that the lagoon is also avoided.’’

He said boiling the water would not remove the toxin, so it should not be consumed at all. ‘‘People should remain out of the waterways until the warnings have been lifted.’’

Environment Canterbury is monitoring the sites and the public will be advised of any changes in water quality.

Environmental scientist Mark Heath said warning signs were being posted along the river between Pomare Bridge and Moonshine Park.

‘‘Algae mats in these areas are thick and starting to peel, which presents danger to swimmers and dogs. We have to be prudent in these circumstances and advise the public that it’s not safe to swim in those stretches of the river.’’

Exposure to potentially toxic algae can cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips.