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The latest weekly samples from Tomahawk Lagoon have shown high levels of the potentially toxic cyanobacteria (blue-green algae) in the upper lagoon.
This follows high levels of the algae being found in the lower lagoon last month and another outbreak last year.
Cyanobacteria can produce toxins which may cause illness, such as skin reactions, in people and animals.
Warning signs put up during earlier outbreaks remained, but more signs would be installed around the upper lagoon.
Otago Regional Council director of engineering, hazards and science Gavin Palmer said the 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 algal blooms were linked to many factors, including high nutrient concentrations in the water and lagoon bed. Nutrients in the lagoon bed were released when strong winds stirred up the sediment.
Council staff would continue to monitor the situation and update the public with developments, he said.
Staff had met representatives of the Tomahawk community this week and would be preparing a paper collating research on the lagoon and blooms done by various organisations over the years for council consideration in April.
After this, a public meeting would be organised to brief all who were concerned, he said.
People could also join the council's email list to receive the sampling results weekly.
Otago Peninsula Community Board member Paul Pope said the meeting with the regional council was about ensuring the community got information about the blooms as soon as possible as well as opening up a dialogue between the council and community about future action.
''We need good liaison with the regional council and its scientists,'' he said.