Eleven-year-old Gabriel Coleman and his friends Maarten and Merel dug through driftwood piled on the shoreline under the Dumbarton Bridge, doggedly on the hunt for pieces of plastic and other debris to fill their white trash bags.

“With teamwork-makes-the-dream-work, we’ve been finding big pieces and small pieces all over,” Gabriel proudly explained.

The trio from Newark was among thousands of volunteers who turned out Saturday for the 39th annual California Coastal Cleanup at 695 beaches, lakes, creeks and rivers throughout the state — including dozens of sites across every county in the Bay Area.

Like many of the other younger volunteers at the Don Edwards San Francisco Bay National Wildlife Refuge in Fremont, they took part in the event as part of their community service responsibilities for school.

“We have to help the community every so often every year,” Gabriel said. “And it’s pretty fun sometimes.”

Since the event began in 1985, more than 1.7 million volunteers have removed at least 27 million pounds of trash from California’s outdoors. But attendance has fallen since the pandemic. Last year, only 38,467 people turned out — about half what it was before COVID. They picked up 308,540 pounds of litter, roughly one-third of the pre-COVID total.

The debris, particularly plastic, not only makes the state’s beaches and shorelines look messy but can also kill wildlife, like birds and sea turtles, which become entangled in it or eat it. Volunteers pick up food wrappers, bottles, cans, cigarette butts and other trash, recording the type and number of items so the Coastal Commission can track pollution trends.

By midmorning on Saturday, around 150 volunteers had arrived for the cleanup at Don Edwards, which Hannah Schmidt, a local park ranger with the California Department of Fish and Wildlife, described as a pretty good turnout.

“Don Edwards is specifically created to help protect endangered and threatened species,” Schmidt said. “And so picking up those microplastics, picking up that trash, directly impacts their habitat within the salt marsh and helps promote the growth of their species.”

Sirisha Maram, a parent and scout leader of Fremont’s Cub Scout Pack 110, oversaw a half-dozen first- and second-grade scouts in bright orange safety vests clean up the wildlife refuge.

“They’re just working along and finding new friends and talking about what they find,” Maram said. “So it’s a very good way for them to find new friends and build a community together.”

Meanwhile, Newark resident Catherine Dorman crouched low to the ground to fish out microplastics hidden under the gravelly shoreline. Dorman, 61, said she joined this year’s cleanup to do her part to help protect local wildlife.

“The bay, this Earth, it’s all we have,” she said.