Toxic algae found in Christchurch waterbodies

Cyanobacteria, a potentially toxic algae, has been found within waterbodies of the greater Christchurch area.

The algae typically presents in rivers as dark brown or black mats, with a slimy or velvety texture and a musty smell. These mats can detach and cause rafts in the water. In lakes, it is often suspended in the water. The algae can make water look cloudy, discoloured, or like it has small globules in it.

Animals can get very sick if they ingest the potentially toxic algae. Unfortunately, dogs love the musty smell of potentially toxic algae and are naturally drawn to investigating it – usually by licking or ingesting the material. It can be quick acting and fatal to dogs. 

Learn more about cyanobacteria.

Christchurch City Council Principal Waterways Ecologist Dr Belinda Margetts says locations of particular risk where potentially toxic algae has been confirmed recently, or last summer, are Hewlings Stream at Jellie Park in Burnside, Yaldhurst Bush, Arthur Adcock Memorial Reserve, and Springlands Reserve.

Te Mana Ora (Community and Public Health) has issued public health warnings for potentially toxic algae at Pegasus Lake and Lake Forsyth.

“This is the time of year when we do start to see toxic algae appearing in our waterways. It is something people should be aware of if they are walking their dogs by rivers, streams, ponds and lakes or engaging in activities, such as kayaking, where they might come into contact with algae in the water,’’ Dr Margetts says.

“As we head into the summer and warmer weather, it is likely that we’ll find more toxic algae, so people need to keep an eye out and avoid contact with any water that may have potentially toxic algae in it.’’

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.