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Published: 2015-01-08 00:00:00

Members of the public are being urged to avoid contact with any reddish water in the Waikato hydro-lakes after tests showed recent discolouration is likely to be caused by a high concentration of the algae Ceratium.

Testing has found high concentrations of the algae at Lake Maraetai and low levels at Lake Karapiro and Ohakuri. More testing is being done at other hydro-lakes.

“Algae experts and public health have advised that this species of algae is not known to produce toxins harmful to health but more tests are being done on this bloom to confirm this,” said Waikato Regional Council’s water, air and waste manager Dominique Noiton.

“In the meantime, it’s suggested people could take a precautionary approach and avoid contact with any reddish water in the lakes.

“The blooms that have been seen are dense in parts and may possibly have irritant effects such as on skin and the respiratory system and so the public may prefer to take a precautionary approach and avoid contact with the water where there are visible blooms or discolouration.”

Testing of lake water by the council followed reports from the public earlier this week about reddish discolouration in lakes Arapuni, Karapiro and Maraetai.

Ceratium is not new to the hydro-lakes but it is usually found at low levels.

Dr Noiton said algae can often “bloom” in waterways during hot summer conditions.

Last summer, a red appearance in water at Lake Waikare in the lower Waikato River catchment was associated with a bloom of the algae Monoraphidium, which isn’t known to produce harmful toxins. Sampling last month indicated Monoraphidium in Lake Waikare was on the rise again.

Anyone concerned about health issues can contact the Public Health Unit of the Waikato District Health Board on the freephone 0800 800 977. For queries specifically regarding the upper Waikato River (from Taupo to Lake Maraetai) contact the Public Health Unit of the Bay of Plenty District Health Board on 0800 221 555. If people have any enquiries about local drinking water supplies they should contact their local district council.