See an algal bloom, give it room

Many types of algae are helpful and important for producing oxygen and food for aquatic life. However, some types of algae can produce toxins that harm humans and animals. As weather patterns shift, harmful algal blooms are becoming harder to predict. Some lakes bloom regularly, some lakes rarely have blooms, and not every bloom is toxic. The only way to know if toxins are present is through laboratory testing. To keep you and your pets safe avoid water with visible algae and follow all posted warnings and closures.

In April, a drought declaration was issued for all watersheds in the state due to low snowpack and multiple years of low precipitation. With less snow melt, we expect rivers and lakes to be shallower, leading to warmer water, lower dissolved oxygen, and making water bodies more susceptible to harmful algal blooms.

As summer approaches, it's important to plan ahead and be prepared for potential blooms, especially during holiday weekends and special events.

What are harmful algal blooms?

Algae include plant-like organisms and bacteria that are a natural part of the ecosystem, but certain conditions can cause algae to multiply too quickly, resulting in algal blooms. This often happens in warm, slow-moving water that is rich in nutrients. Most freshwater harmful algae blooms are caused by cyanobacteria, also known as blue-green algae.

Harmful algae can grow in different parts of a water body. Blooms are often found suspended or floating throughout the water (planktonic zone). However, some harmful algae attach to the river or lake bottom (benthic zone) and form algal mats. These mats can grow on bedrock, vegetation, sand, and other surfaces attached to the bottom. Because the mats are underwater, they are sometimes trickier to spot - the water may look clear even when toxins are present.

Mats (benthic)	Blooms (planktonic)
Does not affect water clarity	Water clarity reduces as bloom density increases
Occur in rivers and lakes (fast and slow flowing water)	Most commonly found in lakes and slow flowing water
Found attached to bottom, floating in clumps, or washed up on shore	Found throughout water column or floating scum on surface

While laboratory testing is the only way to confirm if an algal bloom or mat is toxic, there are a few common characteristics to watch for. Avoid going into water that has:

• The appearance of slimy scum, foam, or thick clumps on the water
• Blue-green, reddish-brown, or pea-soup green colors
• A paint spill appearance on the water
• Swimming, fishing, and shellfish advisories

Possible signs that you or your pet may have been exposed to a harmful algal bloom include:

• Skin rashes after being in the water
• Unexplained sickness after drinking or playing in the water

If you think you or your pet has been exposed to a harmful algal bloom, rinse off with clean water and seek appropriate medical attention. For additional information and guidance, please visit the Department of Health's Harmful Algal Blooms Toolkit.

If you spot a bloom, contact the local water body manager. This could be the county public health department, city, or state park, depending on the water body. Since there is no statewide monitoring program, reporting blooms can be helpful. Check with your local community for more information or monitoring data on a particular lake or river.

What causes an algal bloom?

Human sources of excess nutrients - especially phosphorous - are one of the biggest contributors to algae blooms. These nutrients often enter lakes and rivers through common sources such as:

• Fertlizer runoff
• Failing septic systems
• Stormwater runoff from urban or industrial areas

Even when nutrient levels are stable, unpredictable weather conditions or changes in water flow can trigger blooms. For example, a lake with normal nutrient levels in spring might still experience a bloom in summer due to a storm or urban runoff. Similarly, a lake with high levels of nutrients can avoid a bloom if certain weather conditions are not met.

How do we manage harmful algal blooms?

Local jurisdictions or the "lake managers" decide when to close a lake or recreation area due to toxic blooms based on state and federal guidelines. While Ecology does not make these decisions, we help fund important parts of this work.

Freshwater Algae Control Grant Program

We offer an annual freshwater algae control grant for cities, counties, state agencies, Tribes, and special purpose districts to fund projects that prevent, remove, reduce, or manage excessive freshwater algae growth. For more information about the requirements and eligibility, see our Freshwater Algae Program Grant guidelines and previously funded projects.

Cyanobacteria Toxicity Testing Program

The Cyanobacteria Toxicity Testing Program provides funds for water body managers and residents to test for common toxins produced by harmful freshwater algae. King County Environmental Lab analyzes algae samples from across the state. Ecology funds this testing and shares the laboratory's preliminary results. To receive timely updates about current freshwater algal blooms in the state, join our email list. You can also visit the Washington State Toxic Algae website for more information, including toxin results for your water body, how to report a bloom, and news.

Harmful algal bloom rulemaking

We are considering setting recreational criteria for toxins produced during harmful algal blooms to protect people swimming or doing other activities in or on the water. Following the U.S. Environmental Protection Agency (EPA) recommendations, we plan to consider freshwater criteria for two cyanotoxins: microcystins and cylindrospermopsin. We may also consider developing criteria for other toxins, including anatoxin-a and saxitoxin. Check out the rulemaking webpage for more information.

What can you do to prevent harmful algal blooms?

While harmful algal blooms are hard to predict, there are steps you can take to reduce a lake's chance of developing a bloom.

• Clean up pet waste.
• Choose phosphate-free detergents and soaps.
• Don't over-water lawns and gardens.
• Maintain your septic system to prevent leaks.
• Don't feed waterfowl, like ducks and geese.
• Reduce or eliminate the use of fertilizers.
• Wash vehicles at a commercial car wash or away from storm drains.
• Maintain native vegetation around the lake.

Though predicting harmful algal blooms is difficult, we all play a role in prevention and safety. With awareness and responsible practices, we can help protect Washington's waters for everyone to enjoy.

Water quality