What is Blue-Green Algae?

According to Nova Scotia Environment (NSE), blue-green algae are "a type of microscopic, algae-like bacteria that live in surface water like lakes, ponds, rivers and streams." Warm weather and shallow, slow-moving water that is high in nutrients, such as phosphorous and nitrogen, with sufficient light penetration are all optimal conditions for blue-green algae to reproduce rapidly, forming a large mass (bloom).

While this doesn't occur with every instance of blue-green algae, it can produce harmful toxins. The only way to know for sure is to have the water tested. Until confirmed, it's advised that you do not swim or drink the water. You can report blue-green algae (whether in the form of a bloom in or on the water, or as a mat on the floor of the lake or river) to NSE by calling 1-877-936-8476.

In addition to blue and green, blue-green algae blooms can also be turquoise, olive-green or red in colour. NSE describes them as looking like "fine grass clippings in the water, spilled paint, pea soup or sometimes like a thick scum on the surface." Algae that has matted on the floor of a lake or river can appear black, brown or green and look like clumps of vegetation. Once dried, it can appear brown or grey. You should stay away from them.

Exposure to blue-green algae blooms can cause:

• irritated eyes
• headaches
• fever
• diarrhea and abdominal pain
• nausea and vomiting
• damaged liver if prolonged or high exposure takes place

For more information about blue-green algae, please visit the NSE website at https://novascotia.ca/nse/environmental-health/blue-green-algae.asp#Blue-green-algae