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Blue-Green Algae - Definition

Algae are single celled organisms that resemble bacteria, sometimes joined together in colonies or filaments. They are widely distributed in aquatic habitats and on the damp surfaces of rocks and trees, and in soil. Some species produce toxins which are harmful to human and animal health.

Blue-green algae reproduce rapidly in fresh water when the amount of sunlight, temperature and nutrients are adequate. Within a few days a "clear" lake, pond or ditch can become cloudy with algae growth. This is called a bloom. Blue-green blooms usually float to the surface and can be several inches thick near the shoreline.

A blue-green algae bloom:

  • Is usually very noticeable by the pea-green or turquoise-green colour of the water. It is often mistaken as a paint spill.
  • Is made up of extremely small organisms that are hard to pick up or hold.
  • Can be bright green, or bluish, brownish or reddish green.
  • Is most common in the summer and fall but can occur anytime.
  • Although blue-green blooms can create nuisance conditions and undesirable water quality, most blue-green blooms are not toxic but some are.
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