Swimmer in lake despite warnings

CONCERNS: A woman was spotted swimming in Lake Tutira, ignoring warnings of health risks due to an algal bloom.

A Napier hobby pilot taking an aerial look at the algal bloom in Lake Tutira was stunned to see a woman swimming in the water.

The lake is subject to warnings that people should stay out of the water because of health risks, although the Hawke's Bay Regional Council has confirmed the "dominant species" forming the current bloom is not toxic.

The council says cyanobacteria algae is always present in the lake and could produce a toxic bloom at any time.

Peter Scott flew over the lake last weekend, saw the woman enter the water and from there photographed her swimming out.

He said he was surprised, with the council having issued a warning late last month after an "explosion" of algal bloom, saying its environment science team has found evidence of high phycocyanin, indicating a "potentially toxic" blue-green algae cyanobacteria.

Council environmental scientist Dr Andy Hicks said the current bloom is of Ceratium, a dinoflagellate.

"This is a microscopic organism about 100 microns long or a tenth of a millimetre.

"When similar species bloom in the ocean it is often termed a 'red tide'," he said.

The particular organism is not known to produce toxins, so dogs and wildlife should not be affected, but it can be a nuisance for fish, and produce an unpleasant odour.

But Dr Hicks said potential toxic algal blooms in Lake Tutira can still occur at any time, as explosions in the population of cyanobacteria have happened in previous summers, often after heavy rainfall.

A low biomass of Aphanocapsa, a potentially toxic species of cyanobacteria, was detected alongside Ceratium during the latest sampling.

"We know too well how fast the lake can change when HBRC staff have sampled the lake water and it has been clear, but within an hour a bloom has formed, so it's best for visitors to the lake to treat the water with caution during summer, especially if it is an unusual colour or smell," he said.

Hawke's Bay District Health Board Medical Officer of Health Nicholas Jones said: "Although tests show the current bloom is not dangerous to human health, people should still stay out of the water. Toxic blooms can develop quickly and skin contact can lead to skin rashes or eye irritation."

He said more serious effects can occur if toxins are consumed and there may be some risk also with eating any fish from the lake. If people do wish to eat fish it should be thoroughly gutted and cleaned.

Another issue around the shallows of the lake is 'duck itch', a nasty skin infection caused by a duck parasite.

Signs around the lake warn of the water quality issues. HBRC is continuing a project of computer modelling the lake catchment to assess possible solutions to improve lake water quality.