Health Warning – Algal Bloom in Lake Pegasus

Health New Zealand | Te Whatu Ora has issued a health warning after potentially toxic blue-green algae (planktonic cyanobacteria) was found in Lake Pegasus.

People should avoid the Lake and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.

The type of cyanobacteria that is currently present in high concentrations is:

• Tolypothrix species.

Dr Cheryl Brunton, Medical Officer of Health for the National Public Health Service, says the algal bloom can produce toxins harmful to humans and animals.

“People should avoid contact with the water until further notice.”

“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 them know if you have had contact with the lake water”, Dr Brunton says.

No one should drink the water from the lake at any time. Boiling the water does not remove the toxin.

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.

ENDS