Toxic algal bloom in Lake Pegasus

Tuesday February 13, 2018

Community and Public Health has issued a health warning after potentially toxic blue-green algae (planktonic cyanobacteria) was found in Lake Pegasus.

People and animals, particularly children and dogs, should avoid contact with Lake Pegasus until the health warning has been lifted.

Canterbury Medical Officer of Health Dr Alistair Humphrey says the algal bloom can produce neurotoxins harmful to humans 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 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."

This bloom will be monitored on a weekly basis and the public will be advised of any changes that are of public health significance".

Facts about cyanobacteria

  • Appears as dark brown/black mats attached to rocks along the riverbed.

  • Cyanobacteria occur naturally but can increase rapidly during warmer months.

  • It often has a strong musty smell and algal toxin concentrations can vary over short periods with changing environmental conditions.

  • Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins.

  • If a health warning is in place avoid contact with the water.

  • Although district or city councils may place warning signs, these may not be seen at the numerous river access points, hence the need for people/ dog-walkers to treat every low-flowing river cautiously.

Get further information on swimming water quality in Canterbury (Environment Canterbury). You can also contact Community and Public Health on (03) 364 1777.

Find out more about recreational water issues in your region (Community and Public Health).

Find out safely gathering mahinga kai.

Page last reviewed: 14 February 2018
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