Health New Zealand has issued a health warning for the Hurunui River at SH7 after finding moderate to high levels of potentially toxic algae, known as benthic cyanobacteria.
People are being advised to avoid the area, and animals—particularly dogs—should not be allowed near the water until the warning is lifted. Other access points along the Hurunui River at SH7 may also be affected, and caution is advised for all low-flowing rivers.
Dr Cheryl Brunton, Medical Officer of Health for the National Public Health Service, explained the dangers of the algae, which appear as dark brown to black mats on rocks along the riverbed.
“Exposure may cause skin rashes, nausea, stomach cramps, tingling, and numbness around the mouth and fingertips,” Dr Brunton said. “If you experience any of these symptoms, seek medical advice urgently and inform your healthcare provider if you’ve had contact with algal mats or water in this area.”
Pets that show signs of illness after contact with algal mats should be taken to a vet immediately.
The algae produce toxins that can be harmful to both humans and animals. Environment Canterbury is monitoring the river and will inform the public of any changes in water quality.
Key facts about cyanobacteria:
•Appears as dark brown/black mats attached to rocks.
•Naturally present in low amounts but can grow rapidly in warm, stable conditions with nutrients like nitrogen and phosphorus.
•Often has a musty smell, and toxin levels can vary quickly.
•Detached mats can accumulate on shores, posing a higher risk of exposure.
Health New Zealand advises avoiding contact with the water during the warning period and treating all low-flowing rivers cautiously. Warning signs may not be present at all access points.
For more information, visit LAWA’s website.
