March 27, 2014
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.
ENDS