Crews of volunteers on colorful kayaks scoured Lake Union on Wednesday in search of debris leftover from the July Fourth fireworks show.

They filled bags with about 300 pounds of trash, much of it built up before the holiday. There were traffic cones, shoes, plastic bottles, and some unrecognizable waste.

Puget Soundkeeper Alliance hosts the event every year. The cardboard shells that fall from the sky during the July Fourth show over Lake Union are covered with harmful chemicals.

"It's the debris itself. The cardboard we're not as concerned about, but we are concerned about the chemicals that might be on it. Some of the fireworks have plastic and rubber and nylon rope attached to them. That's really important, because that won't break down. That will stay part of the lake," said Puget Sounkeeper Alliance Director Chris Wilke.

Lake Union is an important ecosystem, especially for fish. Salmon migrating to the Cedar River through Lake Washington pass through Lake Union on their way.

"And right now we have one of the largest runs of sockeye salmon in the lower 48 coming through these waters," Wilke said.

Wednesday's clean-up was the second in a series. For more information on how to volunteer, visit