Toxic algae confirmation sparks river warning


SOUTHLAND’S first toxic algal bloom this season has prompted a warning to swimmers and dog owners.

Environment Southland’s latest monitoring has found elevated levels of toxic algae in the Mataura River.

The latest discovery was near the bridge in Mataura and follows confirmations toxic algae was present in the Riversdale bridge and Gore areas.

Toxic algae, Benthic cyanobacteria, can be recognised at rivers and streams as a green/brown slime on rocks, or dark brown/black mats at the water’s edge.

Several factors can contribute to the growth of toxic algae, such as high levels of nutrients, runoff into waterways, a sudden increase in temperature, and low flows.

Council science manager Elaine Moriarty said it monitored for toxic algae weekly during summer.

“It’s really important that people know what to look for and take a cautious approach to swimming and walking dogs off-lead along rivers as we can’t assess every reach of every river,” Dr Moriarty said.

“Last year we alerted people to toxic algae in a number of rivers, but this year, we haven’t had the right conditions for it to bloom.

“Instead, we’ve had rather unsettled weather and periodic rain which helps to flush any algae away.”

The algae can produce toxins which are harmful to people and animals if swallowed, or through contact with skin.

People and animals, dogs in particular, should avoid contact with the Mataura River until health warnings are removed.

Anyone experiencing health symptoms after contact with contaminated water should visit a doctor immediately

If people are concerned an animal has consumed toxic algae or contaminated water, they should take the animal to a vet immediately.