Potentially toxic algae found in the upper Tomahawk lagoon

The latest weekly samples from Tomahawk Lagoon have shown high levels of the potentially toxic cyanobacteria (blue-green algae) in the upper lagoon.

The cyanobacteria can produce toxins which may cause illness, such as skin reactions, in people and animals.

Otago Regional Council director of engineering, hazards, and science Gavin Palmer said algae had been present throughout the summer, mostly at low levels. It was not possible to predict how long it would take to recede again.

“We are urging parents to keep their children out of the water and dog owners to do the same with their pets,” Dr Palmer said.

The presence of extensive algal blooms or cyanobacteria is linked to many factors, including high nutrient concentrations in the water and lake bed. Nutrients in the lake bed are released when strong winds stir up the sediment.

Dr Palmer said warning signs the council put up at the outlet of the lower lagoon had remained in place since the algae was recorded at high levels there in February.

Additional warning signs were now being installed adjacent to the upper lagoon. All warning signs would remain in place until monitoring showed the algal bloom had reduced and weekly samples were consistently below levels posing any threat to health.

Dr Palmer said ORC staff would continue to monitor the situation and update the public with developments.

Dr Palmer and ORC scientists have met Tomahawk community representatives to discuss the issue. A background paper will be prepared for the council’s consideration and following this, a public meeting will be organised to brief the community.

In the meantime, anyone wishing to join an ORC email list and receive the sampling weekly results should phone ORC customer services on 474 0827.

For more information contact

Gavin Palmer
Director engineering, hazards and science
ORC
Ph 03 474 0827 or 0274 933 960