People are being urged to stay away from Lake Waihola until a warning has been lifted following the discovery of high concentrations of cyanobacteria in the water.
Sampling carried out this week by the Otago Regional Council revealed high concentrations of the blue-green algae which produces toxins harmful to humans and animals and should not be swallowed or allowed to come in contact with the skin.
The council issued a health warning yesterday for the lake. Visitors have been asked not to use it for recreational purposes and obey the cautionary signs until the warning is lifted.
The last time cyanobacteria levels were detected in volumes which required the council's intervention was three years ago. Lake Waihola has a history of cyanobacteria being present and it is tested weekly during the summer months.
The concentration of the algae can change quickly with the environmental conditions.
Dog owners were also warned not to allow their pets to swim in the lake.
Exposure to cyanobacteria can cause rashes, nausea and tingling and numbness around the mouth or fingers.
Eating fish and shellfish from Lake Waihola should also be avoided.
The council said cyanobacteria occurred naturally and it was possible for the concentration to increase rapidly during the summer months.
Visitors were warned to avoid all contact with the water if it was noticeably discoloured or had small globules suspended in it.
Not all cyanobacteria blooms were visible to the naked eye.
Toxins could still persist after the bloom had disappeared.
The public will be advised of any changes in water quality that are of public health significance.
Signs will remain in place until three consecutive samples indicate the volume of cyanobacteria in the water has dropped to a safe level.
Anyone experiencing health symptoms after contact with contaminated water should visit their doctor and contact Public Health South on (03) 476-9800.
