Toxic algae found in Waimea Stream

Environment Southland’s latest monitoring has found elevated levels of toxic algae in the Waimea Stream at Mandeville.

Algae naturally occur in waterways and can flourish during fine conditions, as well as when water flows are low and stable.

Most algae are harmless, however some species can produce toxins and rapidly bloom to high levels. Toxic algae is commonly identified in rivers and streams as a dark green/brown slime on rocks, or dark brown/black mats at the water’s edge.

Environment Southland senior scientist Katie Blakemore said there are many varied factors that lead to the blooming of toxic algae in our waterways.

“Even though we normally see these instances occur over the summer period, it isn’t unheard of to have blooms over the colder months, as one of the key conditions for growth is low and stable water flows.”

The Waimea stream is an example of this, with its recent flows being steady and lower than normal. While lower and stable flows can lead to toxic algae growth, these flows do not necessarily mean that algae will bloom.

“Similar growth is likely occurring in other places along the Waimea Stream, its tributaries, and other rivers in the region.”

“These algae can produce toxins that are harmful to people and animals if swallowed, or through contact with skin. People should keep dogs on a lead and children away from affected areas. It is important to be mindful of the potential health risks, until health warnings are removed.”

If you experience health symptoms after contact with contaminated water, visit a doctor immediately. If you are concerned that any animals have consumed toxic algae or contaminated water, they should be taken to a vet immediately.