Blue-green algae

Did you know, blue-green algae are not algae at all.

They are photosynthetic bacteria (also called ‘cyanobacteria’) that rely on sunlight for energy.

Blue-green algae are present in almost all aquatic ecosystems, including creeks, rivers, lakes and wetlands.

Individual cells are very small, so blue green algae can be present in a water body without being visible.

These cyanobacteria are an important part of a healthy ecosystem. They perform functions like photosynthesis, nitrogen fixation and nutrient cycling in the food chain.

Health risks

Blooms of blue-green algae can pose significant risks to wildlife, pets, and human health by producing toxins.

Blooms also cause water discolouration, scum and odorous compounds.

Blue-green algae toxins can affect us in three main ways:

  • Hepatotoxins damage the liver and may also increase the risk of certain types of cancer.
  • Neurotoxins damage nerves and can cause numbness and muscle tremors
  • Allergens are thought to produce a range of reactions like:
    • skin rashes
    • irritation of the eyes
    • gastroenteritis.

Blue-green algal toxins are colourless, odourless, and can remain present in the water weeks after the algae have disappeared.

They are not destroyed by boiling the water.

Blue-green algae blooms

Blue-green algae can bloom quickly under the right environmental conditions. These include:

  • abundant sunlight
  • warm temperatures
  • still water
  • sufficient levels of nutrients, especially nitrogen and phosphorus.

Nutrients are either naturally present in sediments or wash from the surrounding catchment (agriculture, sewage effluent and stormwater run-off).

What is Council doing?

We regularly monitor our ornamental and recreational waterways for algal blooms.

We put up warning signs when the algal levels are above recommended trigger levels to advise against on-water activities and fishing. These signs advise the presence of blue-green algae and avoiding direct contact with the water for people and pets. Warning signs may need to stay in place for several weeks until the algal concentrations return to safer levels.

For information on the recommended trigger levels, please visit: Seqwater Blue Green Algae Recreation Management Procedure

We are working on improving the health of our waterways and aquatic ecosystems across the city through the Logan Rivers and Wetlands Recovery Plan 2014 to 2024.

Helping prevent blue-green algae blooms

We can help prevent blue-green algal blooms by limiting the amount of nutrients in the water and promoting ecological health.

Detergents and fertilisers contain a high concentration of nitrogen and phosphorus, so we can all play our part by:

  • preventing nutrients from washing into roadside drains (e.g. by washing the car on the lawn rather than on the road)
  • using phosphorus-free detergents
  • reducing the use of fertilisers
  • helping to rehabilitate waterways, and
  • preventing land erosion, where possible, to stop soil washing into waterways.

Reporting blue-green algae blooms

For any algal bloom outbreaks in ornamental or recreational lakes and reservoirs in Logan, please:

To report other algal bloom outbreaks, please visit the Queensland Government website for a list of contacts.

Helpful links

You can visit the below websites for more information: