waskington state lake images
WATERLINE - December, 2014

What is a bryozoan?

by Gene Williams

If you’ve ever seen a light brown, gelati­nous blob in your lake, you may have been looking at a bryozoan. Bryozoans form col­onies, like coral, that consist of thousands of microscopic animals called “zooids” spread around the surface of a hard, jel­ly-like mass. Colonies start out small in the spring, but may grow to more than a foot in diameter.


Bryozoan found in 2014 in Lake Isabella, Mason County (photo courtesy of Erica Marbet).

Bryozoans usually grow around a sub­merged branch, plant stem, or part of your dock. They can be long and thin or shaped like a ball, depending on the surface to which they are attached. Bryo­zoans have tiny tentacles that filter food particles from the water. They thrive in warm water, but don’t grown in bogs or acidic waters.

Though several species of freshwater bryozoans are found in Snohomish County lakes, don’t worry if you see them — they are often found in unpol­luted and silt-free lakes. Some years there are lots of bryozoans and oth­er years they are hard to find. So, when you see a bryozoan, don’t be freaked out. Instead enjoy the amazing diversity of life in our lakes.

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