Health Warning – Algal bloom in Rakahuri/Ashley River at the Rangiora-Loburn Bridge

Our Community and Public Health unit has issued a health warning for the Rakahuri/Ashley River at the Rangiora-Loburn Bridge.

The warning follows identifying moderate to high cover of potentially toxic blue-green algae (benthic cyanobacteria) in the Rakahuri/Ashley River at the Ranigora-Loburn Bridge.

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

People and animals, particularly dogs, should avoid the area of the Rakahuri/Ashley River at the Rangiora-Loburn Bridge until the health warning has been lifted. 

Dr Ramon Pink, 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 Pink 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.”

Dr Pink says people and animals should remain out of the waterways until the warnings have been lifted.

Reticulated town water supplies are currently safe but no one should drink water from the river at any time

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

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

Facts about cyanobacteria:

• Appears as dark brown/black mats attached to rocks along the riverbed.
• A low cover of the algae can occur naturally but can increase rapidly during warmer months. Algal blooms are influenced by a combination of available nutrients in the water and sediments (such as nitrogen and phosphorus), a sustained period of low and stable flows, and favourable weather conditions (e.g. increased temperature, calm days).
• It often has a strong musty smell and algal toxin concentrations can vary over short periods.
• 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.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

ENDS