1 October 2019

Health Warning – Algal Bloom in Lake Forsyth/Te Roto o Wairewa

Canterbury District Health Board’s Community and Public Health unit has issued a health warning after potentially toxic blue-green algae (planktonic cyanobacteria) was found in Lake Forsyth/Te Roto o Wairewa.

People and animals, particularly dogs, should avoid Lake Forsyth/Te Roto o Wairewa until the health warning has been lifted.

Dr Alistair Humphrey, Canterbury Medical Officer of Health says the algal bloom can produce toxins harmful to humans and animals, and 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 your doctor know if you have had contact with the lake water.

“No one should drink the water from the lake at any time. Boiling the water does not remove the toxin,” Dr Humphrey says.

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

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are going to be eaten, remove the gut and liver and wash in clean water before consuming.

Environment Canterbury monitors the lake and advises the public of any changes in water quality that are of public health significance.

This is the earliest seasonal algal bloom warning issued for Lake Forsyth in more than ten years.

Facts about cyanobacteria:
• The algae 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 Community and Public Health on (03) 364 1777:
https://www.cph.co.nz/your-health/recreational-water/

For more information about Mahinga Kai:
https://www.cph.co.nz/wp-content/uploads/saf0112.pdf

ENDS

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