Blue Green Algae

Welcome to the Quick Guide to Blue-green algae . For a more detailed biology of blue-green algae, visit the Detailed Biology - Blue-Green Algae page.

What are blue-green algae? Blue-green algae (or Cyanobacteria) are microscopic, photosynthetic bacteria consisting either of single cells or colonies (groups) of cells. They grow naturally in surface waters in both freshwater and marine systems. Blue-green algae grow in dams, rivers, creeks, reservoirs, lakes and even hot springs .

Identifying Blue-green algae. How do you know if you have blue-green algae? The quick ID guide may help towards identifying your algal problem and what initial action to take. However, only a trained person can make a definite identification and before taking action or beginning any water treatment you should obtain professional advice.(Contacts)

  • Quick ID TEST.
  • Detailed Identification - What Scum is That?

Images of algae


How do blue-green algae grow?

Blue-green algae make their own food through the process of photosynthesis. This process uses light, oxygen and nutrients in the water to make the sugars the cyanobacteria need for growth and cell division. The rate of cell division increases in warmer water, which is why blooms most often occur in summer when the water temperature is higher. However, algae can continue to grow and reproduce in relatively low temperatures.

For optimum growth, cyanobacteria need a high temperature (10 - 35?C), good oxygen supply, high light intensity and nutrients (the most important of which is phosphorous).

How to reduce the growth of blue-green algae - In order to reduce the growth of blue-green algae you need to remove one or more of the factors which enhance algal growth. i.e. 1. Lower the oxygen level, 2. Reduce the light, 3. Lower the temperature or 4. Remove the nutrients. It is not always practical to carry out the first three of these methods of reducing algal growth. However, removal of nutrients is a good way of reducing the growth of blue-green algae.

When conditions for algal growth are right it can only be a matter of days before a 'safe' water supply may have a toxic algal bloom present. It is easier to prevent a bloom than to deal with the consequences after a bloom has occurred.

Further information on algal blooms can be found by visiting these links.

•  What to do if you have blue-green algae in your water supply .



? 2002. NSW Murray Regional Algal Coordinating Committee, MRACC. Unless otherwise specified, maps and images are copyrighted to Department of Land and Water Conservation, NSW.