Algae act like other plants and convert sunlight into energy, forming the base of a lake's food chain. There are many species of blue-green algae found in Wisconsin lakes and rivers, but only certain species can produce the algal toxins that cause illness. Algal blooms can appear and disappear within hours, this is why it is so important to follow a common sense approach. When you see an algal bloom, avoid the water and remember that you should not allow your pets in water where an algal bloom is present! See the links below for more information.