Toxic algae in Te Wairewa/Lake Forsyth
The Community and Public Health division of Canterbury District Health Board has issued a health warning after
potentially toxic blue-green algae (planktonic cyanobacteria) was found in Te Wairewa/Lake Forsyth.
People and animals, particularly dogs, should avoid Te Wairewa/Lake Forsyth until the health warning has been lifted.
The type of cyanobacteria currently present in high concentrations is Anabaena. Anabaena forms green globules that float
in the water column.
Dr Alistair Humphrey, Canterbury Medical Officer of Health, 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 General Practice team immediately and please let your doctor know if you
have had contact with the lake water,” Dr Humphrey says.
No one should drink the water from the lake at any time, Dr Humphrey says. Boiling the water does not remove the toxin.
Animals showing 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 eaten, remove the gut and liver and wash in clean water,” Dr Humphrey says.
Nutrient overload, especially nitrate and phosphorous levels, can contribute to the risk associated with the development
of toxic algae blooms in lakes.
Environment Canterbury will monitor the lake weekly during the bloom and the public will be advised of any changes that
are of public health significance.
Facts about cyanobacteria:
The algae occur naturally but can increase rapidly during warmer months.
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 information visit
http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/lake-warnings.aspx
Or contact Community and Public Health on (03) 364 1777.
ENDS