Toxic Algal Bloom in the Waipara River

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By Robyn Bristow

The Waipara River is the latest North Canterbury river to be issued with a toxic blue-green algae warning.

The Canterbury District Health Board’s Community and Public Health unit says there is a moderate cover of the potentially toxic algae at Teviotdale, but warns the algae could be at other access points along the river also.

People are advised to avoid any contact with the algae, and to keep their animals, particularly dogs, away from the river until the warning is lifted.

No one should drink water from the river at any time.

Toxic . . . Blue-green algae. Photo: Supplied

Dr Alistair Humphrey Canterbury Medical Officer of Health, says the algae looks 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.

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

Facts about cyanobacteria:

brown/black mats attached to rocks along the riverbed.

algae occur naturally but can increase rapidly during warmer months.

has a strong musty smell and algal toxin concentrations can vary over short periods with changing environmental conditions.

high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins.

in place avoid contact with the water.

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.