Health Warning: Potentially Toxic Algae Confirmed In Lake Rotoehu And The Rangitaiki River

Routine water quality monitoring conducted by Environment Bay of Plenty has confirmed the presence of potentially harmful levels of blue-green algae in Lake Rotoehu and in parts of the Rangitaiki River around Murupara. A health warning has therefore been issued by Toi Te Ora -Public Health Service Medical Officer of Health, Dr Phil Shoemack.

People are advised that contact with the water in these areas may be hazardous. Any recreational activity such as swimming which is likely to involve significant contact with, or swallowing of, the water could result in health problems. Toxic algae can trigger asthma and hayfever attacks in susceptible individuals, as well as causing skin rashes, tummy upsets, and even neurological effects such as tingling round the mouth, headaches, general breathing difficulties and visual problems.

As some animals are particularly susceptible to toxic algae, pets and livestock are also at risk.

Algae often multiply to excessive levels during periods of warm, dry, sunny weather when lake and rivers levels are low. In rivers they can form extensive black or brownish slime-like mats that cling to rocks and logs. Significant clumps sometimes break off and float free, eventually collecting on vegetation at the water's edge.

“At this stage it is only Lake Rotoehu and the Rangitaiki River upstream from Lake Aniwhenua which is affected although some of the other lakes in the Rotorua District and other rivers in the Eastern Bay are also showing early signs of algal growth”, says Dr Shoemack.

As a similar problem could occur in other lakes and rivers at any time, Dr Shoemack advises people to make their own visual assessment of the water and avoid diving in if lake water is discoloured or smelly or if black and brown algal mats are found covering large areas of a river bed. People should also avoid swimming in or drinking water that has a strange musty smell.

“Look before you leap” he says. “The toxic algae that form the mats can release toxins that are potentially harmful to people and animals” says Dr Shoemack.

“People need to take steps to prevent animals, both farm stock as well as pets, from having direct contact with the mats by keeping the animals away from the affected stretch of river.” Highest risk areas tend to be shallow river margins where infants and dogs are most likely to come in contact with the mats. “Anyone that usually draws their domestic drinking water from the affected sections of the Rangitaiki River should find an alternative source,” he says.

ENDS

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