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Published: 2003-04-14 00:00:00

Waikato District Health Board is warning duck hunters gearing up for the start of the season in three weeks that algal blooms in the Waikato’s shallow lakes are a danger for them and their dogs.

The naturally occurring blooms, including new species of blue-green algae (Cylindrospermopsis) not previously seen in the Waikato and with potentially severe health effects on humans and animals, now affect lakes Whangape, Waahi, Kainui, Hakanoa and Ngaroto.

Health warning signs were erected at Whangape on Friday warning people not to have contact with the water or take fish, adding to the list of lakes with health warnings.

Medical Officer of Health Dell Hood said duck shooters visiting the lakes over the next couple of weeks to prepare for the shooting season should not have contact with the water, or allow their dogs to drink or swim in the lakes.

Environment Waikato freshwater ecologist Grant Barnes said the algae being seen now in the lakes are likely to disappear naturally once the weather becomes less settled and cooler. At this stage it is not known how rapidly the new algae would respond to changing weather.

Their growth was affected by natural lake processes and further encouraged by nutrients from the local environment and land uses.

“As we’ve found such high levels of algae in these lakes it’s reasonable to assume that they will also be in the many other lakes throughout the Waikato. Like people, animals are sensitive to the effects of algal blooms.

“They are simply not as concerned with the way water looks or smells before they drink it or swim in it.”

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, Canterbury and Otago. There are no short-term measures to get rid of the algae.