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Look out for algae

22 Dec 2017

Look out for algae

As the weather heats up and river water levels drop Council is reminding people look out for the algae Phormidium, which has the potential to turn toxic posing a health risk to people and dogs in particular.

Phormidium is a naturally occurring algae present in stony or braided rivers where it forms a soft, blackish mat on rocks, and blooms more frequently in periods where rivers have low water flows.

It can be washed off and dry on river banks where mats look like dried leaves or cow pats.

“Phormidium is not always toxic, but the best advice we can give is to avoid contact with waterways that have black mats on rocks or on the banks,” says environment an science manager Lois Easton.

The algae has been found in rivers like Motu and Te Arai. Council staff monitor known sites, particularly in places where people swim, fish or where animals drink.

“But because our staff can’t be everywhere, people need to know what to look for and to avoid. 

Dogs appear to be attracted to the drying mats, and are known to get sick from ingesting it. 

Phormidium poisoning in dogs closely resembles heat exhaustion. Owners should take their pets to a vet quickly when they show any unusual symptoms or behaviours. 

“We’d really like people letting us know when they see the mats in a river so we can alert other river users,” says environment an science manager Lois Easton.

“Please be alert and keep children and animals away from the algae if you find it and let Council know.”

More more information about Phormidium

If you think you’ve found Phormidium:

  • Contact Council on 0800 653 800 with the location.
  • If you can, send a photo to service@gdc.govt.nz
  • If you find a large amount of algae, don’t drink from or make contact with the water. Keep animals away.
  • If animals display symptoms like lethargy, muscle tremors, fast breathing, twitching, paralysis, convulsions, contact a vet immediately.
  • If you think you’re experiencing reactions, contact a doctor.
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