Fri, Jan 19, 2024 8:00 AM

Sounding algae alarms


William Woodworth

The public are being warned about algae which council expects to become more of a concern as summer continues.

Council’s monitoring team has noticed toxic algae is starting to become prolific in parts of the Rai River.

In previous summers, algae have also been found in sections of the Wairau and Omaka rivers. This is likely to happen again this summer, staff warn.

Algae can be especially dangerous for children and pets.

Council Environmental Scientist Steffi Henkel says because Council can’t survey all of Marlborough’s extensive stream and river network for toxic algae it’s impossible to put up warning signs at all affected areas.

“Instead we need the community to be aware of the algae, look for it at the river or stream they visit and choose a different site if the algae is present.

“The toxins in the algae can be dangerous for children and dogs.

“If your dog ingests toxic algae you should take it to the vet immediately. Symptoms usually occur within 30 minutes and include panting, lethargy, muscular twitching, paralysis and convulsion.

“In humans, contact with toxic algae can cause vomiting, diarrhoea and skin irritation,” she says.

Dog owners have been seeking alternate sites to help keep their pets cool, with many using Harling Park’s Japanese Gardens as a cool-off spot.

The algae form thick brown or black mats on rocks in the river bed.

These mats have a velvety appearance and can become detached from the rocks. They often accumulate along the water’s edge, where they decay releasing a musky odour, which dogs are attracted to.

The Department of Conservation is calling on people to Check, Clean and Dry gear that has come into contact with freshwater before using it in other lakes and waterways to avoid spreading Lindavia and Didymo algae and other aquatic pests.

“Gear needs to be soaked for just 10 minutes in the 10% detergent solution at the cleaning stations to kill the microscopic algae,” says DOC Nelson Lakes Senior Biodiversity Ranger Melissa Griffin.

“If gear has been dry for at least 48 hours and is bone dry, it is safe to use, but not if dry for less time.

For example, if people have swum in Lakes Rotoiti or Rotoroa one day and they plan to swim elsewhere the next day, their togs should be treated with the detergent solution even if dry.”

You can find out more about toxic algae, including how to identify it, on Council’s website:

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