A team of NOAA divers has just returned from a month-long mission to pull up marine garbage from the ocean floor around Hawaii's Papahānaumokuākea Marine National Monument, a UNESCO World Heritage site and one of the world's biggest marine conservation areas.

NOAA

A marine debris free diver carefully cuts a large mass of fishing net that was found at Pearl and Hermes Atoll.

What they found was "shocking," said Mark Manuel, the mission's chief scientist and operations manager for the NOAA Fisheries Coral Reef Ecosystem Division, especially for such a remote and untouched place, he said.

“Every day, we pulled up nets weighing hundreds of pounds from the corals," Manuel added in a NOAA news release. "We filled the dumpster on [our boat] to the top with nets, and then we filled the decks. There’s a point when you can handle no more, but there’s still a lot out there.”

In all, the team of 17 scientists sailing aboard the NOAA ship Oscar Elton Sette removed some 57 tons of derelict fishing nets and tiny plastic garbage from the monument's chain of tiny islands and atolls, and from its sensitive coral reefs and the shallow waters near its shorelines.

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They spent 33 days on the mission, which began Sept. 25 and ended Oct. 28, during which they found eye-popping amounts of trash, including:

• A 28-ft.-by-7ft. "super net," which extended 16 feet deep and weighed about 11 1/2 tons
• Nearly 6 1/2 tons of trash from the beaches of Midway Atoll National Wildlife Refuge, including innumerable bottle caps and cigarette lighters, which are commonly eaten by birds
• Tens of thousands of pieces of plastic, including 1,469 drink bottles; 7,436 hard plastic fragments; 3,758 bottle caps; and 477 lighters

NOAA has undertaken this mission annually around the monument since 1996, pulling up more than 900 tons of marine debris through the years around the Northwestern Hawaiian Islands, which shelter more than 7,000 species and are home to some of the most pristine, undisturbed coral reefs in U.S. waters.

At one atoll, NOAA's divers helped rescue three sea turtles that had become entangled in derelict fishing nets, which often become wound up together in massive balls when they're discarded by fishing boats that no longer have use for them.

These nets -- and other derelict fishing gear like lines and traps, which can take decades or even hundreds of years to decompose -- threaten not only animals like sea turtles, seals and seabirds, but can also damage corals either by snagging and breaking them off when they drift through the ocean, or by smothering them.

“This mission is critical to keeping marine debris from building up in the monument,” said Kyle Koyanagi, the Pacific Islands regional coordinator for NOAA’s Marine Debris Program.

“Hopefully we can find ways to prevent nets from entering this special place, but until then, removing them is the only way to keep them from harming this fragile ecosystem.”

See the full story at NOAA News, or learn more about Papahānaumokuākea Marine National Monument.

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