Health Warning – Algal Bloom in Hurunui River near State Highway 7 at the Balmoral Swimming Hole

The Community and Public Health division of the Canterbury District Health Board have issued a health warning for the Hurunui River near State Highway 7 at the Balmoral Swimming Hole.

The warning follows finding high levels of potentially toxic blue-green algae (benthic cyanobacteria) in the Hurunui River. Cyanobacteria is currently present in low-flowing channels of the Hurunui River near State Highway 7.

People and animals, particularly dogs, should avoid the area of the Hurunui River until the health warning has been lifted.

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,” Dr Humphrey says.

“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.”

Pets that show signs of illness after coming into contact with algal mats should be taken to a vet immediately.

Dr Humphrey says people and animals should remain out of the waterways until the warnings have been lifted. The algae often accumulates at shallow, slow flowing areas on the edge of the river, so even paddling in the shallows should be avoided.

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

The algae occur naturally but can increase rapidly during warmer months – river users are advised to treat every low-flowing river and river channels cautiously.

Facts about cyanobacteria:

• Appears as dark brown/black mats attached to rocks along the riverbed.
• The algae occur naturally but can increase rapidly during warmer months.
• It often has a strong musty smell and algal toxin concentrations can vary over short periods with changing environmental conditions.
• Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins.
• If a health warning is in place avoid contact with the water.
• Although district or city councils may place warning signs, these may not be seen at the numerous river access points, hence the need for people/ dog-walkers to treat every low-flowing river cautiously.

For further information visit https://www.ecan.govt.nz/your-region/your-environment/water/swimming-water-quality/

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

For more information on Mahinga kai:
Gathering Mahinga Kai

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