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Our vision: A safe and healthy Kitsap County for all.

Cyanobacteria: How to stay safe at the lake

  • katiebaker9
  • 4 days ago
  • 3 min read

Toxic cyanobacteria (blue-green algae) blooms can make people sick and kill animals. 


a yellow warning sign at a lake

It’s a beautiful, sunny day and you’re excited to play at the lake. As you walk to the shore, you notice green scuzz on the water that looks like spilled paint. There’s a yellow sign on the dock that says, “Warning: Toxic algae present. Lake unsafe for people and pets.” 


What is that green stuff in the water? 


Cyanobacteria (toxic blue-green algae) are bacteria that grow naturally in water. Colorful cyanobacteria blooms sometimes appear in local lakes. Blooms can make the water look cloudy or form layers of scum on the water’s surface that look like blue, green, gray or orange paint. Blooms are more common during warm weather but can happen at any time.


Some cyanobacteria blooms produce toxins that can make people sick and kill animals. That’s why it’s important to keep an eye out for algae blooms and other health hazards and be aware of public health advisories.

Stay safe at the lake 


Before your day at the lake, make sure to:


  • Keep an eye out for algae blooms and other health hazards. Do not go in the water if you notice unusual colors, scum, or dead fish or animals. You can report cyanobacteria blooms and other potential health hazards online or by calling 360-728-2235.


  • Check for current lake and swimming beach advisories at kitsappublichealth.org/beaches. Sign up to receive advisories by email or text at kitsappublichealth.org/subscribe.


  • Watch for cyanobacteria (toxic algae) warning signs posted at beaches, docks, and other public access points. During a cyanobacteria bloom:


    • Avoid contact with water in the lake and wash your skin thoroughly if you have contact with lake water.


    • Keep pets and livestock out of the water.


    • If you choose to eat fish caught during a cyanobacteria bloom, remove all fat, skin and organs from the fish and rinse fillets thoroughly.


Examples of cyanobacteria blooms in local lakes.
Examples of cyanobacteria blooms in local lakes.

Cyanobacteria warnings 


When you get to the lake, keep an eye out for warning signs at public docks.


Kitsap Public Health investigates reports of cyanobacteria in lakes with public access. If samples show cyanobacteria in the lake are potentially toxic, we post warning signs at docks, beaches, and other access points, post updates to our website, and send out email and text notifications.

Preventing cyanobacteria 


While cyanobacteria blooms occur naturally, there are steps you can take to help prevent blooms.


Nutrients from landscaping products like fertilizer and lawn additives can wash into the water and contribute to cyanobacteria blooms. You can help prevent blooms by using natural landscaping products and controlling runoff from your property. Learn more at cleanwaterkitsap.org.

Swimming beach monitoring 


In addition to responding to cyanobacteria reports, Kitsap Public Health monitors popular fresh and saltwater swimming areas for fecal bacteria from late May through early September. Fecal bacteria are a sign that there is pollution from human or animal poop in the water. This pollution can carry bacteria, viruses, and other germs that make people sick.


When bacteria levels are high, we post warning signs at swimming beaches, post swimming beach advisories on our website, and send out email and text notifications. Visit our website to learn more about swimming beach monitoring and check for current beach and lake advisories. If a swimming beach is not listed on the water contact advisory page, there is no current advisory for that beach.

More resources 


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