Harmful Algal Blooms

"Harmful algal blooms can produce poisons that are dangerous to people, animals, and the environment. Learn how to keep you and your pets safe.

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 thick green, red, blue, or brown layers in the water that look or smell bad. However, sometimes they contain poisons that hurt 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. Also, not all blooms are easy to see—poisons can be present even when you can’t see the bloom.

Be Aware of Harmful Algal Blooms

Harmful algal blooms can produce poisons that can make people and animals sick. They also can block sunlight in a body of water or use up a lot of the oxygen, which kills fish and plants in the water. Harmful algal bloom poisons have caused the shutdown of the water supply in a major U.S. city, killed wildlife and pets, and sickened hundreds of people with a variety of skin, respiratory, neurological, and abdominal symptoms. Evidence suggests that harmful algal blooms are increasing in number and severity because of farming practices, storm water runoff, wastewater overflows, and increasing temperatures..."

Algal blooms