Warning from experts regarding Canterbury water quality

Water testing equipment. Source: Eurofins New Zealand.

Water testing equipment. Source: Eurofins New Zealand

As hot weather hits, experts urge swimmers and pet owners to be diligent when it comes to checking water quality.

Nineteen waterways across Canterbury and South Canterbury are under temporary or permanent toxic algae (cyanobacteria) warnings due to health risks.

Toxic algae form as thick, dark brown mats over rocks in rivers and in lakes. Suspended, it creates cloudy discolouration.

Shirley Hayward, ECan’s Science Team Leader of Water and Ecoloy explained that toxic algae can form naturally from warm weather, stable river flows, a lack of floods, and high nutrient levels.

It poses risks to both humans, dogs, and livestock, with a fifty-cent-sized piece enough to kill an average sized dog if ingested, said Hayward.

“Dogs love the smell of toxic algae and will seek it out, even if it’s present in only a very small amount,” said Hayward.

Large blooms can also cause harm to fish by reducing oxygen levels in water.

ECan monitors water in popular freshwater recreation spots weekly over the summer. This is done to warn the public and to help create regulations regarding the nutrients that enter waterways. ECan also works with individual landowners to mitigate and reduce waterway contaminants.

In humans, symptoms caused by toxic algae range from allergic reactions, eye irritation, rashes, nausea, and diarrhoea to tingling sensations around the nose and mouth, said Dr Cheryl Brunton.

Brunton told Canta there had already been one reported case of cyanobacterial poisoning this year. While Brunton said the risk for most people is minor and transient, more severe cases are treated on a symptomatic basis.

When toxic algae is found in Canterbury, ECan, Te Whatu Ora, Te Mana Ora and relevant territorial authorities work to spread warnings to the public through signage, print, press releases, Facebook posts, and updating the Land and Water Aotearoa (LAWA) Can I Swim Here site, said Hayward.

With the risk of toxic algae becoming more prevalent due to factors like climate change, both Brunton and Hayward urge swimmers and pet owners alike to check sites like LAWA and familiarize themselves with the signs of toxic algae.