Keeping your dog safe from algal bloom

STAYING OUT: Richard Oldfield never lets his dog Redun go into Henley Lake, which has a toxic algae problem at the moment. PHOTOS/VOMLE SPRINGFORD

The toxic algae which seems to curse Henley Lake every year is back once again, posing a threat to people and their pets.

A health warning is in place after toxins related to the decay of algal blooms were discovered in the lake and Masterton District Council is warning people not to let their dogs off their leads around it.

It is popular with dog walkers as it's one of the only places in Masterton where dogs can be exercised without a leash.

The toxic algae, also known as cyanobacteria, occurs naturally but increases rapidly during summer months, said Grant Hathaway, parks and facilities manager for the council.

He said the toxins had caused "a thick surface scum" on parts of the shoreline and light blue, white streaks of decaying cells releasing their pigments had also been observed.

This was a common occurrence during bloom decline, he said.

"If the water is cloudy, discoloured, or has small globules suspended in it, avoid all contact.

Mr Hathaway said not all cyanobacterial blooms were visible to the naked eye however, and toxins can persist after the bloom has disappeared.

Regular dog walkers at the lake yesterday were not too worried about the warning, although they took precautions.

Rod Fleury, who was walking his dog Maisie on a leash, said she'd had never been sick but she wasn't much of a water dog. "I think we are always careful, it's the people that don't have their dogs on a lead that get into trouble."

He was used to the warnings and said he had noticed some years were worse than others. "The water level has dropped which means the water is more stagnant."

Richard Oldfield said he didn't let his dog Redun, who he was walking without a leash, near the lake anyway. "I'd never let the dog in the lake."

He said Redun had never been sick after many years walking around the lake and rivers. "As long the river is flowing, I don't worry."

Dog owner Christine Fisher was walking her dog Sophie without a leash and had only just heard about the warning.

"I know each summer it's a problem, it's just what you expect."

She said she didn't want her dog going into the lake anyway as it didn't look clean.

Sophie sometimes drank from rivers but was more interested in chasing rabbits than swimming, she said.

"Hopefully the Ruamahanga stays clean."

Mr Hathaway said the council will continue to monitor the lake during summer and advise the public of any changes. "Cyanobacterial concentrations can change quickly with changing environmental conditions, for example, wind."

River swimming spots are monitored for toxic algae by Greater Wellington Regional Council.

A warning for the Waipoua River was issued on December 24 but has since been lifted.

The risk factor is determined by measuring the proportion of the river bed covered by cyanobacteria as well as the amount of cyanobacteria mats washed up on the river's edge.