Harmful algae and cyanobacteria (sometimes called blue-green algae) can produce toxins (poisons) that can make people and animals sick and affect the environment. Do all you can to protect yourself and your pets.
Algae and cyanobacteria are simple, plant-like organisms that live in the water. Algae and cyanobacteria can rapidly grow out of control, or “bloom,” when water is warm, slow-moving, and full of nutrients. Blooms can occur in fresh water, salt water, and brackish (a mixture of fresh and salt) water around the world. Blooms sometimes look like foam, scum, mats, or paint on the surface of the water. They can even make the water appear different colors, including green, blue, red, brown, or another color.
Blooms of algae or cyanobacteria can be harmful to people, animals, or the environment if they
- produce toxins (poisons)
- become too dense
- use up the oxygen in the water or
- release harmful gases
Blooms can occur more often or become more severe with warmer water temperatures or if the amount of nutrients in the water increases. Levels of nutrients increase when fertilizer, sewage or runoff get into the water.
Animals can get very sick or even die quickly after exposure to harmful algae and cyanobacteria. Seek veterinary care immediately if your pets or livestock seem sick after going in or near water. Animals can die within hours to days of swallowing toxins. Animals are often the first affected, in part because they are more likely to swim in or drink from bodies of water that contain harmful algae or cyanobacteria.