Warning to look out for toxic algae in Christchurch waterways

Christchurch City Council is warning residents to look out for toxic algae in waterways after it was recently spotted in Wigram Pond.

Head of three waters Brent Smith said the toxic algae cyanobacteria appears in the city's waterways every summer and the recent hot and dry weather has made it more prevalent than usual.

Smith says the potentially toxic algae has been confirmed in at least one pond and could be present in others.

"Animals can get very sick if they ingest the algae, and dogs are naturally drawn to investigating its musty smell. If dogs lick or ingest the material it can be quick acting and fatal.” 

"Potentially toxic algae has recently been seen in Wigram Pond, but it’s important to remember that it can be present in any freshwater waterbody so learn what to look out for, and if in doubt keep your dog away from the water,” Smith said.

"The algae typically presents in rivers as dark brown or black mats, with a slimy or velvety texture and a musty smell. The algae can make water look cloudy, discoloured, or like it has small globules in it."

Te Mana Ora (Community and Public Health) has issued public health warnings for potentially toxic algae in a number of waterways across Canterbury:

Temporary health warnings

Water testing indicates moderate to high cover of toxic algae (benthic cyanobacteria) at these locations:

  • Rakahuri/Ashley River at Rangiora-Loburn Bridge – issued 20 December 2023
  • Rakahuri/Ashley River at SH1 – issued 5 December 2023
  • Waihao River Gum Tree Flat Road (Don's Hole) – issued 14 December 2023
  • South Bank Tributary of the Waiau/Uwha River above the Waiau Bridge – issued 13 December 2023
  • Temuka River at SH1 Bridge – issued 23 January 2024
  • Ōtipua/Saltwater Creek at SH1 Bridge and rowing club – issued 2 February 2024
  • Opihi River at Raincliff Bridge – issued 17 January 2024
  • Opihi River at Saleyards Bridge – issued 4 January 2024
  • Opihi River at Grassy Banks – issued 11 December 2023
  • Opihi River at SH1 – issued 5 December 2023
  • Waikirikiri/Selwyn River at Upper Huts – issued 18 January 2024
  • Waikirikiri/Selwyn River at Whitecliffs – issued 5 January 2024
  • Waikirikiri/Selwyn River at Glentunnel – issued 6 December 2023
  • Pareora River/Pureora at Pareora Huts – issued 1 December 2023
  • Pareora River/Pureora at SH1 – issued 1 February 2024
  • Waihao River at Bradshaws Bridge – issued 1 December 2023
  • Hae Hae Te Moana River – issued 21 November 2023

Cyanobacteria poisoning symptoms
Symptoms of cyanobacteria toxin poisoning in animals include lethargy, muscle tremors, fast breathing, twitching, paralysis, and convulsions. If you suspect your dog is suffering from cyanobacteria poisoning, contact your vet immediately. 

For humans, if you have been in contact with water containing cyanobacteria, you may experience tingling or numbness around the fingertips and/or mouth, breathing difficulty, gastrointestinal symptoms, or skin rashes. If you feel any of these symptoms after contact with a waterbody, seek medical advice from your doctor or contact Healthline on 0800 611 116.