December 23, 2015

Health warning for Kahutara River and Lagoon

The Community and Public Health division of the Canterbury District Health Board has issued a health warning after potentially toxic blue-green algae (Phormidium, a type of benthic cyanobacteria) were found in the Kahutara River near

State Highway 1, Peketa. Benthic algal growth occurs on or just above a river, lake or sea bed.

Dr Alistair Humphrey, Canterbury Medical Officer of Health, says people and animals, particularly dogs, should avoid the water in the Kahutara River near SH1 and the Lagoon until the health warning has been lifted.

The presence of toxic Phormidium algae extends from the main stem of the river down into the Lagoon south of the Peketa camping ground.

“River users should keep an eye out for dark brown or black mats, growing most extensively upstream of the Lagoon. Given that the mats are detaching, they will be accumulating in the Lagoon, so I would also advise that the Lagoon be avoided.”

Exposure to benthic cyanobacteria 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,” he says.

“Boiling the water from the river does not remove the toxin and it should therefore not be consumed under any circumstances. Contact with the skin or eyes should also be avoided.”

Animals showing any signs of illness after coming into contact with algal mats should be taken to a vet immediately.

Dr Humphrey says 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.

Facts about cyanobacteria:

• If a health warning is in place avoid all 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 with caution.

• Cyanobacteria occur naturally but can increase rapidly during warmer months.

• Colonies appear as dark brown/black mats attached to rocks along the riverbed.

• Cyanobacteria often have 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 then accumulate along the shore and increase the risk of exposure to toxins.

For further information visit

http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/toxic-algae.aspx

http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx

or contact Community and Public Health on (03) 364 1777.

ENDS

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