MEDIA RELEASE
24 January 2019
For immediate release
Health Warning – Toxic Algal Bloom in Selwyn/Waikirikiri River downstream of the Glentunnel Swimming Hole
Canterbury District Health Board’s Community and Public Health unit have issued a health warning after potentially toxic
blue-green algae (benthic cyanobacteria) were found in Selwyn/Waikirikiri River downstream of the Glentunnel Swimming
hole.
People and animals, particularly dogs, should avoid the area of the Selwyn/Waikirikiri River downstream of the
Glentunnel Swimming hole until the health warning has been lifted.
There are also other access points along the Selwyn/Waikirikiri River that may have cyanobacteria present and people are
advised to check for the presence of cyanobac-teria and avoid contact.
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 ar-ea.”
The Selwyn District Council as the drinking water supplier are following agreed proce-dures and monitoring their nearby
drinking water intakes.
“No-one should drink the water from the river at any time, even after boiling the water from the river, it does not
remove the toxin therefore should not be consumed,” Dr Humphrey says.
Pets should be taken to a vet immediately if they are showing signs of illness after coming into contact with algal
mats.
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:
• 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 accumu-late 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 eve-ry low-flowing river cautiously.
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