Harmful Algal Blooms (HABs) and Health

What to know

Harmful Algal Blooms (HABs) are where algae grow rapidly in bodies of water and produce toxins that can be detrimental to human and animal health and ecosystems. These blooms can occur in various aquatic environments, including freshwater lakes, rivers, and marine coastal waters. HABs can look like foam, scum, or paint on the surface of the body of water. They can also grow underneath the water which can make it difficult to notice. While not all algal blooms are harmful, blooms of algae can harm people, animals, or the environment if they:

• Make toxins
• Become too dense
• Use up oxygen in the water
• Release harmful gases

Understanding HABs

• Types of algae: HABs are typically caused by species of cyanobacteria (blue-green algae), dinoflagellates, and diatoms, which produce toxins under certain conditions.
• Toxin Production: Toxins can accumulate in water, affecting fish, shellfish, and other aquatic organisms. Some toxins are also harmful to humans and animals through direct contact or consumption of the contaminated water or seafood.
• Conditions: HABs often thrive in warm, nutrient-rich waters with low flow conditions.

Where HABs are found

HABs can grow in fresh or saltwater, or a mixture of both which is known as brackish water, these can include waters used for recreation and drinking. HABs can be found world-wide and, in the United States, they have been reported in all 50 states, Puerto Rico, and the U.S. Virgin Islands.