Problems and risks with blue-green algae

Toxins in blue-green algae may harm human and animal health if allowed to multiply to large numbers.

Problems with blue-green algae

A number of environmental conditions need to be in place for an algal bloom to occur. These include sunlight, nutrients as well as weather and flow conditions that lead to separation of the water into layers, usually with a layer of warm surface water which does not mix with a colder deeper layer.

Blue-green algae thrives in the warm surface layer of a water body that forms, usually, from spring through to autumn throughout Australia’s inland waters. Blue-green algae possess gas pockets which prevent them from sinking so that they remain in the surface layer and can access the abundant light near the water surface, leading to rapid growth.

Potential risks

If blue-green algae multiply to high numbers, toxins may be produced causing health problems for people, domestic animals and stock that come into contact with the algae.

Contact with the algae by recreational users can be harmful. There have been reports of skin and eye irritations, nausea, vomiting, muscle weakness or cramps by some people who have swum through algal scum or swallowed it.

Blue-green algae blooms can cause:

  • harmful human health effects
  • death of livestock, domestic animals and wildlife
  • bad odours
  • fish kills
  • closure of water storages for drinking or recreational use
  • higher water treatment costs.


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