WALTHAM —

The work Rob Mark and about a dozen of his friends did Saturday had them shaking their heads - in consternation and amazement.

Mark, pastor of the First Presbyterian Church on Alder Street, plucked trash out of Purgatory Cove on the Charles River. In this case, "trash" included recliners, tires, even motorbikes.

"It's pretty horrific stuff," said Mark.

"Sadly, we pull out tires, shopping carts, all sorts of stuff. There's a lot of beer bottles, fishing oars, plastic straws and bottle caps, shovels, cigar containers. It's all an indication of our throw-away, consumer culture," Mark said.

Every year, volunteers take out plastic bottles, Styrofoam, "tons of Dunkin' Donuts cups," and other non-biodegradable garbage, he said.

"It's certainly educational for all of us, to watch our ecological footprint and recycle so we're not contributing more to the deluge of (trash)," Mark said.

Mark kept a bag of the trash collected from the Charles River, and planned to bring it to his church service yesterday, he said.

Each church member took a piece of trash out of the bag and put it into a recycling bin as a symbolic gesture and kind of "confessional," Mark said.

The Earth Day river cleanup on Saturday was part of a wide-scale effort of at least 3,600 volunteers, spread along the Charles, from Boston to Hopkinton, he said.

Mark's group of 30, which included children as young as 4 years old, City Councilor Steve Rourke, and a dog, was the best turnout for the annual cleanup in six years, Mark said.

"Personally, it feels very good to be a minister whose group shows up for these events and cleans up the community," Mark said.

The First Presbyterian Church and other faith organizations expanded Earth Day to Earth Week, wanting to devote more energy to the environment.

"Earth Week reminds us that the Earth is God's household and the home of all people. At the same time, the global recession, the housing crisis and Haiti remind us that all people need homes. Ecology and economy can never be separated," said Alexander Levering Kern, executive director of Boston's Cooperative Metropolitan Ministries and a chaplain at Brandeis University.

At First Presbyterian Church, the environment is never far from consciousness, Mark said.

"We as a church are really committed" to caring for the environment, he said.

Every Sunday, the church holds a "Watershed service," and they pull out a map of the Charles River watershed, he said, "just to remind ourselves we're sitting here on the Earth and we are stewards and called to take care of it."

The church considers the Charles River Watershed to be "sacred," Mark said.

It is a lifeline to many creatures in the community, including people, he said.

Tom Monteleone, a member of the Island Neighborhood Association, said he's been helping clean the river for about 15 years, because, he said, "it's part of our backyard."

On Saturday, he said, he mostly picked up plastic from Cram's Cove area of the river on Woerd Avenue.

"It's amazing the amount of plastic in there," Monteleone said.

Association members also took chairs, a motorcycle frame, a bicycle, and other assorted items out of the Charles, he said.

"I don't know where these things come from," Monteleone said.