Cyanobacteria appear as dark brown/black mats attached to rocks

Toxic algae warning

by Laurie Willetts

The Community and Public Health division of the Canterbury District Health Board has issued a health warning after potentially toxic blue-green algae was found in Selwyn River at Glentunnel.

People and animals, particularly dogs, should avoid the area of the Selwyn River at Glentunnel until the health warning has been lifted. There are other access points along the Selwyn River that may have cyanobacteria present and people are advised to check for its presence and avoid contact.

“The algae look like dark brown to black mats and can produce toxins harmful to people and animals,” says Canterbury Medical Officer of Health Dr Cheryl Brunton.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms, visit your doctor immediately. Let your doctor know if you have had contact with dark brown/black algal mats or water in this area.”

The Selwyn District Council as the drinking water supplier is following agreed procedures and monitoring its 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.

“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.

Cyanobacteria appear as dark brown/black mats attached to rocks along the riverbed. The algae can increase rapidly during warmer months and often has a strong, musty smell. Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins. Avoid contact with the water. Warning signs may not be seen hence the need to treat every low-flowing river cautiously.

For further information, visit Environment Canterbury — Swimming Water Quality, CDHB — Recreational Water or LAWA — Can I swim here.