Cyanobacteria Phormidium

Phormidium is a type of cyanobacteria (algae) that’s widespread throughout lakes and rivers around New Zealand, including those with very good water quality.

Staff are identifying sites in our region to monitor the algae, particularly during the low-flow season in summer. If it blooms in large quantities, it can pose a health risk. 

What it looks like and where it's found

Phormidium looks like a dark brown leathery mat and is typically found on rocks in stony riverbeds. Blooms increase normally during summer when the river and stream flows are low.

What's the risk to health?

With increased growth, the algae can start to produce cyanotoxins which can be toxic to dogs, livestock and people.

The algae mats can come loose and settle on riverbanks and shallow areas where animals are more likely to consume it. Dogs are attracted to its musty smell, it can be fatal to them if eaten. If animals display symptoms like lethargy, muscle tremors, fast breathing, twitching, paralysis or convulsions, contact a vet immediately. 

You can also be at risk from illness if you come into contact or drink the water from rivers with high concentrations of the algae in it.

Reactions to the cyanobacteria can include stomach and intestinal illness, trouble breathing, skin irritation and neurotoxic reactions like numbness and tingling.

Always check areas in waterways where people and animals frequently go and if you think you’re having a reaction, contact a doctor. 

If you think you’ve found Phormidium

Contact us with the location and a photo would be great.

If there’s a large amount of algae, don’t drink or make contact with the water and keep animals away.