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Reminder – Health Warnings in place for Algal Blooms at various sites in Canterbury

Thursday 21 February 2019Media release3 minutes to read

THIS IS AN ARCHIVED PAGE. The advice and information contained in this page may not be current and it should only be used for historical reference purposes.
A number of health warnings still remain in place for algal blooms in Canterbury

A number of health warnings still remain in place for algal blooms in Canterbury

Canterbury District Health Board’s Community and Public Health unit would like to remind the public that health warnings are still in place for a number of Lakes and Rivers in the Canterbury district.

The warnings to remain out of the following waterways due to ongoing algal blooms are still in place at the following sites:

  • Te Roto o Wairewa (Lake Forysth)
  • Te Waihora (Lake Ellesmere)
  • Lake Pegasus
  • Rakahuri (Ashley) River at SH 1 bridge
  • Rakahuri (Ashley) River near Rangiora-Loburn Bridge
  • Waipara River at Teviotdale
  • Waikirikiri (Selwyn) River downstream of the Glentunnel swimming hole
  • Waihao River near Bradshaws Rd, South Canterbury
  • Lake Rotorua (Kaikoura)

“Many of these waterways have been in bloom for some time now and will continue to be so with the warm weather we have been experiencing” says Dr Alistair Humphrey, Canterbury Medical Officer of Health.

People and animals, particularly dogs, should avoid these waterways until the health warning has been lifted as the blooms can produce toxins that are 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 these waterways,” says Dr Humphrey.

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

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 eaten, remove the gut and liver and wash in clean water.

Further information on gathering Mahinga Kai can be obtained below.

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

Facts about cyanobacteria:

  • The algae occur naturally but can increase rapidly during warmer months.
  • If lake 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.
  • River algae blooms appear as dark brown/black mats attached to the rock in the riverbed.  These mats can detach and accumulate along the riverbanks and therefore increase the risk of exposure to toxins.
  • 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:

Or contact Community and Public Health on (03) 364 1777:

For more information about Mahinga Kai:


For further information, contact:
Canterbury DHB Media Advisor

027 567 5343


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Page last updated: 30 July 2020

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