Toxic algae returns to Wairarapa and Hutt rivers as weather heats up and water levels drop

Thursday, 7 January 2021

River-users and dog owners are being warned to be vigilant after toxic algae was detected in Wairarapa and Hutt Valley waterways.

Swimmers and dog owners are being warned to keep clear of the water at some Wellington region rivers following the detection of toxic algal blooms.

Blooms have been found in the Waipoua River in Wairarapa, and Te Awa Kairangi Hutt River between Birchville and Manor Park, and the Pakuratahi River at Kaitoke campground, both in the Hutt Valley.

The Greater Wellington Regional Council said in a statement the reoccurring issue is a result of water temperatures getting warmer and river levels drop during summer.

The council’s senior environmental scientist, Dr Mark Heath said the algae is toxic to humans and dogs.

* Dog owners told to stay away from Wairarapa river covered in toxic algae

Dogs are predominantly at risk because they like the smell and taste of toxic algae. An amount the size of a 50 cent piece, can be enough to kill a dog.

* Toxic algae at extreme levels in Kāpiti and Wairarapa: more than half of riverbeds covered

“Toxic algae has increased to dangerous red alert levels in the Waipoua River over the last week, with detached mats washing up at the river’s edge, so we strongly advise against swimming and letting your dog off the leash.”

Dogs are predominantly at risk because they like the smell and taste of toxic algae. An amount the size of a 50 cent piece, can be enough to kill a dog.

The risk of coming into contact with the algae was likely to increase as the weather got warmer, he said.

Algal mats grow on the rocks in the riverbed and form leathery dark green or black mats. They can break away and accumulate at river edges. As they dry out they can become light brown colour, and have a distinctive deep earthy or musty smell.

The council urged the community to check for LAWA website warnings and alerts.

The council has further warned bacteria from leaking pipes or run-off can contaminate swimming areas after heavy rain.

“In general, a good rule of thumb is to stay out of fresh or sea water for 48 hours after rain, and always check for warning signs,” Heath said.

The council advises if a person has been in contact with toxic algae and are feeling unwell, they should see their doctor or ring Healthline on 0800 611 116. Anyone with breathing difficulties or convulsions should seek urgent medical attention. If a dog is believed to have swallowed toxic algae, advice is to take it to the nearest vet immediately.