What is blue-green algae (BGA)?

Blue-green algae (known scientifically as Cyanobacteria) is a natural type of organism present in aquatic systems, including streams, lakes, estuaries, and the sea.

Blue-green algae can exist in both salt and fresh water and form part of a natural ecosystem. Individual cells are very small and are normally not visible in a water body. However, under certain environmental conditions, numbers can increase rapidly and blooms become easily visible across the water surface.

What causes an algae bloom?

Many factors trigger blue-green algae blooms and they usually occur because of a combination of the following: high nutrient levels, warm weather conditions, increased light conditions, low storage volumes. Blue-green algae blooms generally occur over the summer period.

What types of algae are found in Lake Illawong?

Algae are a diverse group of organisms which range dramatically in size, shape and toxicity. A few different families of blue-green algae most commonly identified in water quality tests are:

• Aphanocapsa
• Planktolyngbya
• Microcystis.

Is blue-green algae in the Lake Illawong a risk to my health?

There are non-toxic and toxic forms of blue green algae. The majority of algae blooms in the Lake Illawong have been non-toxic types; however the current bloom is a type that may produce toxins.

The toxins that some algae produce can affect humans. If ingested, symptoms include nausea, headache, vomiting, abdominal pain, diarrhoea, gastroenteritis, muscle weakness. Contact with the body has been found to cause skin, throat, ear and eye irritations in some people.

What can I do to make sure I am not at risk?

Observe the Melbourne Water signage that is in place at the Lake Illawong. When there is a potentially toxic type of blue-green algae, avoid contact with the water. The signs are an important part of the Victorian Government’s blue-green algae management system. They help people make their own decision about whether to come in contact with the water.

When there is a bloom, Melbourne Water undertakes weekly testing and will remove the warning signage once the levels have returned to normal.

For more information contact 131 722 or visit melbournewater.com.au.