Key messages

  • Algae-affected water may not be suitable for drinking, recreation or agricultural use.
  • Contact with affected water can cause skin irritation, mild respiratory effects and hayfever-like symptoms.
  • Ingesting toxins can cause gastroenteritis symptoms, such as vomiting, diarrhoea, fever and headaches.

Blue-green algae (cyanobacteria) is a type of bacteria with traits of both bacteria and algae. It can be found in almost all water systems, and can appear individually or in a group.

Blooms

In appropriate conditions, blue-green algae can grow rapidly and form visible blooms, or scums. Blooms are usually somewhere between dark green and yellowish brown, and can turn the surrounding water green.

Blooms generally occur during summer and autumn, when nutrient levels are high, temperatures are warm, and the water is relatively still. Weather conditions, nutrient levels and water flow will affect how long a bloom lasts.

For the latest information on blue-green algae blooms, or to inform the water management authorities of an outbreak, contact the water body’s manager. Managers may be located at local councils, water corporations, or the Department of Environment, Land, Water and Planning.

Health effects

Water affected by blue-green algae may not be suitable for drinking, recreation or agricultural use.

Some species of blue-green algae produce harmful toxins which take effect when eaten, inhaled or skin contact is made. Contact with affected water can cause skin irritation, mild respiratory effects and hayfever-like symptoms. Ingesting toxins can also cause gastroenteritis symptoms, such as vomiting, diarrhoea, fever and headaches. Toxins can also have an effect on the liver and the nervous system.

Avoid contact with algae-affected water, particularly in areas with visible scums or discoloured water. Follow the advice on any nearby signs and keep out of the water until authorities advise the risk has passed.

If you come into contact with affected water, you should remove any affected clothing and wash yourself thoroughly with clean water. Affected wetsuits should be rinsed in fresh water to remove any trace of algae.

If you have any problems, you should seek medical advice.

Pets can be poisoned from contact with toxic algae, which could potentially kill them. Do not let your animals swim or drink in algae-affected areas. If your pet does come into contact with affected water, wash them thoroughly with fresh water before drying so they do not swallow algae while grooming their fur. If you are concerned about your pet’s health, see your vet as soon as possible.

Livestock owners should continuously check water supplies for blue-green algae. Livestock should be kept away from any algal blooms.

Water supplies

Blue-green algae can affect the taste and odour of a water supply.

If your local water corporation supplies your drinking water, they will manage any associated risks through their risk management plan.

Do not drink, or otherwise use, untreated water. Boiling algae-affected water will not inactivate its toxins – only adequate treatment will suffice.

To keep algae from growing in your private drinking water supply, make sure that no light can enter the pipes or fittings, and make sure the tank is sealed.