KIRKLAND, Wash — Kirkland residents are wondering why they have been seeing foam on the surface of Lake Washington.

According to an ecologist from the King County Department of Natural Resources and Parks, the foam residents have seen is part of a natural process.

However, man-made soaps and detergents can also cause something that looks a little similar. King County officials say it's a good idea to make sure the foam residents are seeing is the harmless kind.

According to Daniel Nidzgorski, an ecologist with King County, the natural foam gathers when plants and algae growing in the lake break down, releasing natural oils and chemicals into the water. This disrupts the water much like soap does to make bubbles.

"Really, this is something that people should go take a look ...," Nidzgorski said. "If it's shiny like rainbows, probably a soap. If it smells like perfumes, it's probably a soap detergent of some sort. But this stuff, it's usually thicker, sometimes a little bit brownish, it smells a lot more like a lake then like a laundry room." 

Nidzgorski said residents will see more of this on Lake Washington because of its size, providing a bigger area for wind to whip up the foam that builds up along the surface.

If the foam sticks around for a while that's usually a good sign because the natural foam takes longer to break down than the kind created from man-made soaps and detergents.

Nidzgorski said it is important that residents know the difference.

"If they've taken a look and it looks like a soap or detergent, and not like this natural lake foam from plants, then they can call their city or call us at King County," he said. "That's something we do want to know about, because then it is a spill that we should track down and see what the problem is."