Water quality

Cyanobacteria are a form of microscopic organisms that can produce toxins harmful to the health of humans and animals exposed to or swallowing the water where the organisms are growing.

Optimal conditions for cyanobacterial blooms occur when a perfect storm of nutrients from surrounding farmland combine with sunlight and warm water temperatures in the shallow peat lake. This environment also promotes bacteria such as E. coli to multiply.

Potentially toxic algae, known scientifically as cyanobacteria, are naturally occurring in rivers and lakes in New Zealand, including waterways with good water quality. Most of the year it is present in lakes at low levels that are not much of a danger. But algae can be a problem during the summer months, when warm temperatures and nutrients in the lake create an environment where it can thrive, forming extensive blooms which can be toxic to humans, dogs, livestock and wildlife.

Scientists do not yet understand when and why this algae turns toxic, so to be safe, always treat it as toxic.

Dogs are particularly susceptible to poisoning from toxic algae as they may drink lake water or play in the water.

Symptoms in humans may not appear until sometime after contact with the affected water. Symptoms include tingling and numbness around the mouth and fingertips. Rashes, skin and eye irritation; allergy symptoms such as hay fever and asthma; nausea and possibly stomach upsets, including diarrhoea and vomiting. If you think you have come into contact with cyanobacterial blooms, shower and change your clothes as soon as possible. Long-term exposure to cyanobacterial toxins may cause additional health risks.