Harmful algae

Blue-green algae in freshwater

Despite their name, blue-green algae are actually types of bacteria known as Cyanobacteria.

Some species have the potential to produce toxins. This cannot be determined by ‘naked eye’ inspection; only a laboratory analysis can verify the potential for toxicity.

Immediate action

If you suspect that blue-green algae have infested a water source used for drinking, stock watering or domestic purposes, you should refrain from using that water until a suitably trained person has identified the algae.

Please note: boiling the water will not solve the problem.

Blue-green algal blooms

An algal bloom is a mass of algal cells which discolour the water, form scums, produce unpleasant tastes and odours, and seriously reduce the water quality.

Not all blue-green algal blooms are toxic. Those that are may change their toxicity slowly over a period of weeks to months.

Blue-green algal blooms often persist for several weeks, depending mainly on the weather or flow conditions. Cooler, windy weather or increased flow may reduce or prevent blooms from occurring.

As the bloom dies, the cells tend to become 'leaky'. If the bloom contains species that produce toxins, these will be released into the surrounding water. Once released, some toxins may persist for more than three months before sunlight and the natural population of bacteria in the water degrade them.

Related information

In this guide:

  1. Blue-green algae in freshwater
  2. Reporting outbreaks
  3. Health effects
  4. Livestock and farm dams

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