11 January 2017
Cyanobacteria found in Lake Waihola
Sampling carried out by the Otago Regional Council has shown high concentrations of cyanobacteria (blue-green algae) at
Lake Waihola and a health warning has been issued for the lake. Visitors are advised not to use it for recreational
purposes and observe warning signs until the warning has been lifted, while dog owners are also being warned to avoid
allowing their pets swim in the lake until then as well.
Lake Waihola has a history of cyanobacteria being present, however the last time it was present in volumes requiring ORC
intervention was three years ago.
Cyanobacteria can produce toxins that are harmful to humans and animals if swallowed or through contact with skin (such
as may occur when swimming, water skiing or kayaking). Exposure to cyanobacteria may cause symptoms such as skin rashes,
nausea, tummy upset, and tingling and numbness around the mouth or tips of fingers.
Anyone experiencing health symptoms after contact with contaminated water should visit their doctor and also contact
Public Health South on (03) 4769800 to provide them with information about those symptoms.
Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and
liver and wash in clean water.
Cyanobacteria occur naturally but can increase rapidly during summer months. If the water is cloudy, discoloured, or has
small globules suspended in it, all contact should be avoided. Not all cyanobacterial blooms are visible to the naked
eye and toxins can persist after the bloom has disappeared.
Cyanobacterial concentrations can change quickly with changing environmental conditions (eg wind).
ORC monitors cyanobacteria weekly at Lake Waihola during summer, and the public will be advised of any changes in water
quality that are of public health significance. Signage alerting the public to the presence of cyanobacteria will remain
in place until three consecutive samples indicate it is safe.