MEDIA RELEASE

Algae levels slower to build in some Rotorua lakes

For immediate release: Wednesday 21 January 2003

While levels of toxic blue-green algae are building in three of Rotorua’s most vulnerable lakes, they are still generally lower than at the same time last year, Environment Bay of Plenty reports.

However, changes in the weather may quickly alter the situation, warns environmental scientist Matthew Bloxham. The National Institute of Water and Atmospheric Research predicts more anticyclones and settled weather, conditions that favour the forming of blue-green algae blooms. “So we could see accelerated bloom development then. We have some good news now, but the situation may quickly change.”

Mr Bloxham says the regional council’s ongoing monitoring has shown a general build up of potentially toxic blue-green algae in lakes Rotoehu, Rotoiti and Rotorua.

So far, lakes Rotoiti and Rotoehu are faring slightly better than last summer, Mr Bloxham says. “Windy weather appears to be stalling bloom development on Lake Rotoiti. The flipside to this is that these winds can drive large numbers of blue-green algae inshore, which is what’s happening at the moment in the Ruato Bay-Hinehopu area.”

Earlier this summer, similar conditions produced “reasonably spectacular but short-lived” blooms at Ngongotaha and Holden’s Bay in Lake Rotorua.

Although localised blooms are developing in some of Lake Rotoiti’s more sheltered bays, algae numbers actually dropped last week in Okawa Bay and Te Weta Bay. The health warnings issued for these bays in late December are still in place.

Last summer, the Medical Officer of Health issued health warnings for the whole of Lake Rotoiti on January 24. Lake Rotoehu followed in mid-February and Lakes Rotorua and Tarawera were also affected by isolated health warnings for a time.

Environment Bay of Plenty has stepped up its lakes’ monitoring regime this year, increasing the number of sampling sites and testing weekly initially instead of fortnightly. “We need to keep pace with any bloom development as much as we can,” Mr Bloxham says.

ENDS

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