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Algae are simple plants that grow with light and nutrients. Most algae are safe and are a natural part of aquatic ecosystems. Some however can produce toxins that can be damaging to humans, domestic animals and livestock that drink or come in contact with the water, as well as to organisms living in water. These algae can be found in freshwater as well as brackish and marine waters.

Blue-green algae are actually bacteria and in favourable conditions such as high temperatures and nutrients, can grow excessively (blooms) and may produce toxins which in extreme cases can be lethal. Marine blooms are often mistaken for oil or slimy effluent slicks on beaches and in rivers where it has been blown onshore by winds and tidal movements. It decays rapidly, usually turning greenish and then pink/red as it dies. It also smells offensive, like rotting plant matter or chlorine gas.
All blue-green algae blooms should be treated as potentially toxic to humans and animals, and the water should not be used for potable water supply (without prior treatment), stock watering, or for recreation. NSW Health advises that any domestic use (including drinking) of surface water without treatment should be avoided at all times.

Who to Contact

Toxic algae can only be positively identified by trained personnel. If you suspect that there is a blue-green algal bloom in a water body, you should contact:

  • Councils Environmental Health Services on (02) 6670 2400.
  • NSW Office of Water - Algal Information Hotline on 1800 999 457 (free call).

Further Information

  • The NSW Office of Water website provides up-to-date information for NSW on the algae situation. This site also includes tips for identifying algae, key contacts for more information, impacts of blue-green algal blooms, and locations where a red or amber alert is in place.
  • NSW Primary Industries
  • NSW Health website provides information regarding cyanobacteria and drinking water.

Last Updated: 23 May 2016