A health warning has been issued for the Ashburton River at Hills Road following the discovery of potentially toxic algae.
People should avoid the area and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.
The warning by the Canterbury District Health Board follows the finding of moderate to high cover of the algae benthic cyanobacteria.
There are also other access points along the Ashburton River at Hills Road that may have benthic cyanobacteria present. People are advised to treat every low-flowing river cautiously, check for the presence of benthic cyanobacteria and avoid contact.
Canterbury medical officer of health Dr Ramon Pink said the algae looked like dark brown to black mats and could produce toxins harmful to people and animals.
“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, 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.
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.
A health warning has just been lifted at Lake Clearwater, where potentially toxic blue-green algae (planktonic cyanobacteria) was found before Christmas.
Facts about cyanobacteria:
Appears as dark brown/black mats attached to rocks along the riverbed.
A low cover of the algae can occur naturally but can increase rapidly during warmer months. Algal blooms are influenced by a combination of available nutrients in the water and sediments (such as nitrogen and phosphorus), a sustained period of low and stable flows, and favourable weather conditions (like increased temperature, calm days).
It often has a strong musty smell and algal toxin concentrations can vary over short periods.
Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins.