| 01 Mar 2023

27.07.23 - This Health Warning has been lifted

Health Warning – Algal Bloom in Lake Opuha

Te Mana Ora | Community and Public Health has issued a health warning after potentially toxic algae scums (planktonic cyanobacteria) were found in Lake Opuha.

People should avoid contact with the lake and downstream water bodies until further notice and animals, particularly dogs, should also not be allowed near the water until the health warning has been lifted.

“When a bloom of potentially toxic cyanobacteria is present in a lake, there is a possibility of cyanobacteria and toxins being transported downstream,” says Dr Matthew Reid, Medical Officer of Health, National Public Health Service, Te Whatu Ora.

“It is particularly important to note that no one should drink the water from the lake or any downstream waterbodies at any time. Boiling the water does not remove the toxin.

“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 and please let your doctor know if you have had contact with the lake water.”

Animals that show signs of illness after coming into contact with algal mats or scums should be taken to a vet immediately.

Environment Canterbury monitors the lake weekly during summer and the public will be advised of any changes in water quality that are of public health significance.

Facts about cyanobacteria

  • Cyanobacteria occur naturally but can increase rapidly during warmer months.
  • Algal blooms are caused by a combination of nutrients in the water (such as nitrogen and phosphorus), and favourable weather conditions (e.g. increased temperature, calm days).
  • If the water is cloudy, discoloured, or has small globules suspended in it, avoid all contact.
  • Not all cyanobacterial blooms are visible to the naked eye and toxins can persist after the blooms disappear.
  • Cyanobacterial concentrations can change quickly with changing environmental conditions (e.g. wind). If a health warning is in place avoid contact with the water.

For further details visit: https://www.lawa.org.nz/explore-data/canterbury-region/

Or contact Te Mana Ora on (03) 364 1777: https://www.cph.co.nz/your-health/recreational-water/

For further information, contact:

Karen Berry
Communications Manager
Te Whatu Ora
South Canterbury  
021 139 7442