Canterbury District Health Board’s Community and Public Health unit have issued a health warning after potentially toxic blue-green algae (benthic cyanobacteria) were found in Selwyn/Waikirikiri River, downstream of the Whitecliffs Domain near the picnic area.

People and animals, particularly dogs, should avoid the area of the Selwyn/Waikirikiri River downstream of the Whitecliffs Domain near the picnic area until the health warning has been lifted.

There are also other access points along the Selwyn/Waikirikiri River that may have cyanobacteria present and people are advised to check for the presence of cyanobacteria and avoid contact.

Dr Alistair Humphrey, Canterbury Medical Officer of Health, says the algae look like dark brown to black mats and can produce toxins harmful to people and animals.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips.

“If you experience any of these symptoms, visit your doctor immediately, also let your doctor know if you’ve had contact with dark brown/black algal mats or water in this area,” says Dr Humphrey.

The Selwyn District Council as the drinking water supplier are following agreed procedures and monitoring their nearby drinking water intakes.

“No-one should drink the water from the river at any time, even after boiling the water from the river, it does not remove the toxin therefore should not be consumed,” Dr Humphrey says.

Pets should be taken to a vet immediately if they are showing signs of illness after coming into contact with algal mats.

People and animals 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.

Facts about cyanobacteria:
• The algae occur naturally but can increase rapidly during warmer months.
• Algal blooms are caused by a combination of nutrients in the water (such as nitrogen and phosphorus), and favourable weather conditions (e.g. increased temperature, calm days).
• If the water is cloudy, discoloured, or has small globules suspended in it, avoid all contact.
• Not all cyanobacterial blooms are visible to the naked eye and toxins can persist after the blooms disappear.
• Cyanobacterial concentrations can change quickly with changing environmental conditions (e.g. wind). If a health warning is in place avoid contact with the water.

For further information visit: https://www.lawa.org.nz/explore-data/canterbury-region/

Or contact Community and Public Health on (03) 364 1777:
https://www.cph.co.nz/your-health/recreational-water/

For more information about Mahinga Kai:
https://www.cph.co.nz/wp-content/uploads/saf0112.pdf

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