Cyanobacteria (blue-green algae) are a common seasonal occurrence in Victoria and a natural component of most aquatic systems, including streams, lakes, estuaries and the sea.

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, or scums, become easily visible across the water surface.

Algal blooms can have an unsightly appearance, ranging in colour from dark-green to yellowish-brown and develop a paint-like consistency as they dry out. They also often have a pungent smell.

Many factors trigger blue-green algal blooms including, but not limited to, nutrient levels, low inflows, low storage volumes and warm weather conditions.

The presence of significant numbers of blue-green algae in water bodies can produce toxins that can have serious health implications to humans, animals, birds, livestock as well as significant environmental impacts.

In Victoria, blue-green algae are monitored regularly by water corporations and local waterway managers. When sampling and testing have confirmed the existence of blue-green algae, appropriate action is taken based on the use of the water body and the density and nature of the bloom.