Water Quality photo identifier

Water Quality Program

Aquatic Plants, Algae, and Lakes

As a user of the Aquatic Plant, Algae and Lakes web pages, we would like your input!

We are currently looking for ways to improve the user experience on these pages.

If you have a few minutes, we would appreciate your taking the time to fill out our survey. Results from the survey will be used to help us determine how to improve the user experience. Thank You!


Washington is fortunate to have over 7,800 lakes which provide a variety of recreational opportunities for Washington residents as well as a diversity of ecological habitats. Many of Washington's lakes have good water quality, but lakes in more urbanized watersheds may suffer from nutrient enrichment. Nutrients from agricultural areas, stormwater runoff, urban development, fertilized yards and gardens, failing septic systems, land clearing, municipal and industrial wastewater, runoff from construction projects and recreational activities all contribute to accelerated enrichment. As lakes become nutrient-enriched, they produce more algae and aquatic plants. They may also produce more fish.

This website provides links to environmental monitoring information about lakes and lake educational materials.

Freshwater Algae:

Algae are a source of food and energy for fish and other lake organisms and are a vital part of all lakes, but nuisance types of algae can interfere with lake uses. Some species of algae - blue-green algae (also called cyanobacteria) release toxins. Unsightly scums are usually caused either by tangled masses of filamentous green algae or by "blooms" of certain blue-green algae that float on the lake surface forming scums. The regular occurrence of visible algal blooms often indicates that lake nutrient levels, especially phosphorus, are too high.

This website provides information about Ecology's freshwater algae identification and toxicity testing program, management methods, and human health concerns about cyanobacterial toxins.

Saltwater Algae (sea lettuce):

Beaches in Puget Sound are fertile grounds for blooms of sea lettuce (several species of the genus Ulva). Sea lettuce, because of its rapid growth rate and thin leafy structure, can accumulate rapidly in thick piles driven by winds and ocean currents. Sea lettuce grows in shallow bays and inlets when the long hours of bright sunlight of the summer combine with a lack of wind and an influx of nutrients from a variety of sources. All types of seaweeds, including sea lettuce, are essential components of the Puget Sound ecosystem. They provide food for several species of sea birds, fish, and other marine animals, as well as shelter for several fish species. At times, sea lettuce accumulates on beaches and its decay can release unpleasant odors.This website provides information on the Saltwater Algae grant program funded for the 2009-2011 biennium.

For additional information about marine algae blooms, see the discussion here: Marine Algae Blooms

Aquatic Plants:

Like algae, aquatic plants play a vital role in lake ecology because they provide cover, habitat, and food. However, too many plants can limit swimming , fishing, water skiing, boating, and aesthetic appreciation. Exotic species, plants, like Eurasian watermilfoil introduced into habitats where they are not native, are considered to be severe threats to our lakes. In the absence of predators, diseases, and competitors from their native habitat, non-native species introduced into new habitats over overrun their new home and crowd out native species. It is very difficult to eradicate these species once they become established.

Ecology surveys Washington lakes each year to document the density and species of aquatic plants in each water body. See this information, Ecology's plant identification manual, and management techniques at this website.