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Published: 2003-03-28 00:00:00

There’s no immediate solution for algal blooms in shallow Waikato lakes, according to Environment Waikato.

The naturally occurring blooms – the latest a strain of blue-green algae in Lake Waahi not previously seen in the Waikato and with potentially severe health effects on humans – have occurred periodically during summer for many years. They are likely to disappear naturally once the weather becomes less settled and cooler, although it was not known how rapidly the species would respond to changing weather.

Environment Waikato freshwater ecologist Grant Barnes said the algal bloom occurred naturally in freshwater lakes especially during periods of warm settled weather, and their growth was affected by natural lake processes and further encouraged by nutrients from the local environment and land uses.

Water quality at Lake Waahi had improved measurably since the 1970s and ‘80s as a result of regulatory changes which had improved the discharge from coal mining activities, he said.
“Blue-green algal blooms are common throughout New Zealand at this time of year and have been reported recently in the Bay of Plenty, Manawatu and Canterbury. There are no short-term measures to get rid of the algae.

“We’re aware that these blooms seem to be reported more frequently but it may be because we’re better at detecting them, or that the public have higher expectations of clean water so they are more likely to report them.”

He said that if climate change predictions came true such blooms may become a regular summer event.

Environment Waikato had tested the Region’s lakes in January after a bloom developed in the Waikato River but blue-green algae were not a concern at Lake Waahi then so the growth had occurred in the last six weeks.

Blooms in other lakes in the Region had led to health warnings at Lakes Hakanoa, Kainui and Ngaroto.