Algae Control Program photo

Algae Control Program

Freshwater Algae Control

Most types of algae are harmless and some are important to lake productivity. But many Washington lakes and rivers have excessive algae growth, and in the right conditions clear water can become cloudy with algae within only a few days. Algae can be smelly and unsightly as well as being toxic to humans, pets, and livestock.

What is an Algae Bloom?

For more information about toxic algae, go to the Washington State Toxic Algae program

When a species of algae reproduces rapidly and reaches high concentrations, it is called an algae bloom. Too much phosphorus and nitrogen (found in fertilizers, animal waste and sewage) leads to perfect conditions for algae blooms. While blooms happen mostly in the summer or fall, they can occur any time of year.

Why is Ecology particularly concerned about blue-green algae?

Blue-green algae can be toxic and are actually bacteria called cyanobacteria. People and animals may become ill or worse after exposure to toxic blue-green algae, including stomach pains, vomiting, diarrhea, skin rashes, and nerve and liver damage.

Although most blooms are not toxic, toxicity is hard to predict. A single species of algae can have toxic and non-toxic strains and a bloom that tests non-toxic one day can become toxic the next day.

Blue-green blooms may float to the surface and can be several inches thick near the shoreline. A blue-green algae bloom often looks like green paint floating on the water and is hard to pick up or hold.

Ecology's Aquatic Algae Control Program

Ecology's algae control program provides local governments with the tools they need to manage algae problems:

Join Ecology's Freshwater Algae Program email newsletter

To receive toxicity reports about freshwater algae blooms, join our Listserv:


Lizbeth Seebacher

Banner photograph courtesy of professional photographer Bruce Andre (