Harmful algal blooms are a rapid growth of algae or cyanobacteria that appear like foam, paint, or scum on the surface of water. These blooms can be of various colors and occur in both freshwater and saltwater. Harmful blooms produce toxins harmful to people and animals who come into contact with tainted water.
The AVMA webpage covers the various kinds of HABs and the diseases they cause. The page also includes reporting procedures to state and federal agencies.