Blue-Green Algae: What is it?

Blue-green algae is not actually algae, but a type of bacteria called cyanobacteria. It is harmful to livestock and humans when it produces toxins, which happens as the cyanobacteria dies off. These toxins can attack the liver and nervous system and cause sickness or even death. Some common signs that an animal has ingested these toxins include staggering, gastroenteritis, convulsions and difficulty breathing.

Blue-green algae typically forms in nutrient-rich fresh water sources when daytime temperatures are warm or hot. It can start forming in June and can occur throughout the summer.

There are many species of blue-green algae that can take on different appearances. It can look like a blue-green shimmering paint across the water’s surface, it may look like pea soup or it could also look like grass clippings floating in the water (among other forms). One way to help identify if it is blue-green algae is to do the “finger test”: if you scoop your hand through the water and the algae does not clump up on your hand (meaning it is filamentous or strand like) but instead it flows through your fingers, it is likely blue-green algae.

It is difficult to get a lab test to confirm the presence of blue-green algae in a water body so controlling the growth becomes very important. This can be done through the treatment of a water body with existing blue-green algae growth or through prevention of growth in the first place.

The most effective products for treating blue-green algae contain copper sulphate. After the bloom is treated and the bacteria begins to die, it releases toxins. It is recommended to keep animals out of a treated water source for 14 days after treatment to prevent them from ingesting any toxins. A water source may need to be treated more than once throughout the grazing season.

Prevention is the safest and most cost-effective way to keep blue-green algae from forming in your water sources. Reducing the amount of nutrients that enter the water will limit the growth of algae (both blue-green and green). This means preventing fertilizer and manure runoff from entering the water. This could be done through not allowing livestock direct access to the water and by keeping the surrounding riparian area in healthy condition. The use of an aeration system can also help prevent the development of algae.