Cyanobacterial Bloom Basics:

Cyanobacteria (also called blue-green algae) can grow quickly, or bloom, when water is warm, slow-moving, and full of nutrients. Cyanobacterial blooms are most commonly found in fresh water, such as lakes, rivers, and streams. These blooms can discolor the water and look like foam, scum, mats, or paint on the surface, but some blooms are hard to see because they grow below the water's surface. These blooms sometimes produce toxins (cyanotoxins) that can be lethal to animals. 

You cannot tell if a bloom is toxic just by looking at it. When in doubt, it's best to stay out!

If your pet becomes ill hours to days after potential exposure, contact your veterinarian immediately.