A biologically rich coral island chain in the Pacific Ocean northwest of Hawaii, which President Bush designated as a marine national monument, is under assault from floating garbage ranging from plastic bottlecaps to baby diapers.

Hailed by environmentalists as one of the president's most enduring contributions to the environment, the Montana-sized monument includes uninhabited islands home to some 7,000 marine species, at least a quarter of which are found nowhere else on earth.

But the new national monument also resides on the edge what marine scientists call the great "eastern garbage patch": a section of slowly rotating Pacific Ocean currents – or gyre – double the size of Texas that acts as a giant garbage collector.

Sitting between Hawaii and northern California, the patch's sluggish currents wash onto the Northwestern Hawaiian Islands Marine National Monument. That 1,200-mile-long island chain north of Kauai acts as the teeth of a giant comb, straining onto its otherwise pristine beaches and coral reefs floating trash, such as syringes, bags, six-pack rings, and tons of fishing nets and other gear.

Concern about the problem has risen to such a level that Congress has acted on it. On Sept. 27 the House passed a bill that would give a lift to struggling ad-hoc efforts to clear debris from the Northwestern Hawaiian Islands. Their move follows the Senate's approval of the legislation last year. Observers are optimistic that the bill will be finalized, and Mr. Bush will sign it into law after the November election.

It would not be a moment too soon, experts say. About 3 million tons of the trash floating in the garbage patch is plastic, estimates Charles Moore, founder of the Algalita Marine Research Foundation in Long Beach, Ca., who has traversed the gyre on research expeditions.

Samples he collected in a recent study showed that there were more tiny bits of plastic by weight than there were plankton per cubic meter of sea water.

"It's a toilet that never flushes, but just keeps accumulating," he says of the patch. "If you're an organism in this area you have six times as much chance of bumping into something plastic as you do something natural."

Globally, millions of tons of trash enter the ocean each year. Between 60 and 80 percent of it is land-based, washing into streams and rivers and finally the ocean from landfills, storm water discharges, litter, and sewage overflows.

The rest is from ocean-based operations, including fishing gear, junk from oil and offshore mineral exploration, illegal offshore dumping, and shipping containers washed overboard.

A container of thousands of plastic yellow toy ducks bound from China to the US was lost in the Pacific Ocean in 1992, but made news in 2003 when the ducks began washing up in Europe. Examples of trash slopping onto US beaches have included Nike running shoes, Lego building blocks, umbrella handles, and hockey gloves, experts say.

Old "ghost" fishing nets adrift in the sea and smaller plastic objects are special hazards for marine birds and mammals because birds tend to gobble colored plastic until they die. These hazards can have lasting effects on the monument since many species call the region home.

"Marine debris has a tremendous impact on the monument because of what's there in terms of wildlife," says Seba Sheavly, coordinator of the National Marine Debris Monitoring Program, a program funded by the Environmental Protection Agency. "We have a critical situation for Hawaiian monk seals that are horribly depressed in number. In the very place where the young are learning to fish and play, it's where these old nets get caught."

Animals are not all that get snared. In August 2005, a Russian minisubmarine became snagged in an old fishing net 625 feet below the Pacific Ocean surface before being rescued. Cargo ships with propellers bound up in miles of old net pull into Hawaii for repairs, says Christine Woolaway, the Kalaeloa, Hawaii-based coordinator for the Northwestern Hawaiian Islands cleanup.

But it was the heart-wrenching pictures of animals snarled in plastic packaging and old fishing lines that first grabbed public attention in the 1970s.

As of this past summer at least 130 countries including the US had ratified international agreements. Hundreds of thousands volunteer for regular worldwide beach cleanups sponsored by the Ocean Conservancy, an environmental group that tracks marine debris.

Yet political action, public attention, and cleanup funding have waned in the past decade, overshadowed by issues such as climate change and declining global fisheries. But hurricane Katrina, which pushed tons of debris into the Gulf of Mexico, and the new national monument, have helped give the issue some attention.

A debris-marine bill sponsored by Sens. Daniel Inouye (D) of Hawaii and Ted Stevens (R) of Alaska, was approved by the Senate last year.

Then, last month, the House unanimously approved the legislation, which sends $15 million and a mandate to the National Oceanic and Atmospheric Administration, US Coast Guard, and other agencies to rev up their garbage compactors.

It also provides modest grant funds for research, sets up a trash-tracking database, and mandates that federal agencies educate the public.

"We need some help, that's for sure, because there's more debris out there on those islands than any one agency can handle," says Ms. Woolaway.

Since 1995, at least 680 tons have been removed in the cleanup along the islands – much of it in old nets. With little landfill space in Hawaii, an automotive salvage company shreds the nets with the residue burned to make electricity in an electric company boiler.

But even after a thorough cleanup, the next year tons more debris wash ashore from the eastern garbage patch.

"Every single piece of trash on the beach or in the water has a person's face behind it – it's that simple," Ms. Sheavly says. "The cigarette lighters, shampoo bottles – the animals on the island didn't do that. It comes from improper waste management practices. This is a fixable problem, and the answer is simple: We've got to have more awareness and give people an opportunity to change their behavior."