Visitors ignore lake health warnings

Stand at any boat ramp at Lake Rotoiti over the holiday period and it would be hard to believe an algae bloom health warning was in place.

People were busy manoeuvring boat trailers into the Rotorua lake, narrowly missing the Ministry of Health signs alerting lake users to the latest increase of cyanobacteria (blue-green algae).

"I have anecdotal evidence that people will ignore any sign they choose to ignore, and health warning signs about lake waters are no different," said Rotorua District Council's Jim Nicklin.

Mr Nicklin said the latest health warning was posted on December 22 after weekly sampling by Environment Bay of Plenty reported large numbers of algal cells.

New health warnings were issued for Lake Rotoiti (Okere Arm, Okawa Bay, Te Weta Bay), Lake Rotorua (Ngongotaha, Holdens Bay, Ohau Channel), Lake Rotoehu (Te Pohu Bay) and Lake Okaro.

Environment Bay of Plenty said exposure to blooms might cause skin rash, nausea, tummy upset; spark hayfever or asthma; and could affect the nervous system (tingling and numbness around the mouth or tips of fingers).

Glancing down into the pea-green soupy water at Te Weta Bay the dense white algae globules reflected the light.

In the same instant a couple launched their kayaks and wobbled off, slicing their paddles through the algae.

Heading away from Lake Rotoiti's western edge, the water returned to its enticing clear blue. Speed boats buzzed, towing ski-biscuits and wake-boarders, and children sprinted off the end of jetties.

Mr Nicklin said the lake was a popular spot for visitors during the holidays.

"A lot of out-of-towners own lakeside properties and come here for their Christmas and New Year break."

He agreed it would be hard to imagine people resisting the temptation to play in the water.

"So the general message is people should have a look at the water and if it doesn't look flash, don't get in.

"The blooms can quickly spread from one bay to another so users must be cautious at all times."

He said wind could sweep a large amount of algae into a bay in a matter of hours, causing it to build up to potentially harmful levels.

"But it's possible blooms could develop independent of these areas and unassisted by the wind."

Environment Bay of Plenty says some symptoms arise from the presence of the bloom, and others from a further release of toxins.

"These toxins are colourless and odourless. They're unaffected by boiling water and can persist in the water after the bloom has subsided," the Environment Bay of Plenty website reported. "The medical officer of health advises against drinking water from the lakes at any time."

However, Mr Nicklin assured trout lovers the fish were safe to eat as long as they were gutted.

- NZPA