"Harmful algal blooms can produce toxins that are dangerous to people, animals, and the environment. Learn what harmful algal blooms are, how you and your pets can avoid them, and what CDC is doing to protect the public’s health.
Warm weather brings many happy occasions: picnics, ballgames, and back yard fun. It also is a time when microscopic plant-like organisms – algae and cyanobacteria – are more likely to overgrow in rivers, lakes, and oceans.
These overgrowths, called algal blooms, occur across the country. Sometimes they are just eyesores – an unpleasant scum or mats of green, red, blue, or brown organisms in the water that look or smell bad. Sometimes they also cause harm to people, animals, and the environment. In this case, they are known as harmful algal blooms. But you can’t tell if a bloom is harmful just by looking at it..."