Health Warning – Algal Bloom in Waipara River at Teviotdale Bridge

Thursday December 22, 2011

​​The Community and Public Health division of the Canterbury District Health Board have issued a health warning after potentially toxic algae (benthic cyanobacteria) were found in the Waipara River at the Teviotdale Bridge.

People and animals, particularly dogs, should avoid the Waipara River at Teviotdale Bridge until the health warning has been lifted. 

Canterbury Medical Officer of Health Dr Alistair Humphrey says the algal mats can produce toxins harmful to humans 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.”

No one should drink the water from the river at any time, Dr Humphrey says.

“Boiling the water from the river does not remove the toxin. However, reticulated town water supplies are currently safe,” he says.

Animals should be taken to a vet immediately if they come into contact with the contaminated rivers.

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

Facts about cyanobacteria:

  • Appear 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 to treat every low-flowing river cautiously.​

Page last reviewed: 11 February 2014
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