"Global ocean currents carry the marine debris to the Northwestern Hawaiian Islands, which are like the picket fencing stopping sand and snowdrifts," said Cousteau.
The currents are collectively known as the Pacific Ocean gyre. They push trash from the Pacific coasts of the Americas, Asia, Australia, and Russia into a convergence zone which shifts in and around the vicinity of the Northwestern Hawaiian Islands, said Brainard. During el Niño years, the zone shifts into the main Hawaiian Islands.
Fishing nets discardedaccidentally or on purposeby vessels in distant fisheries produce the most damage to the pristine coral reefs. As the gear drifts with the surface currents it snares other debris, forming large clumps that extend 30 to 50 feet (10 to 15 meters) into the ocean, explained Brainard.
As the mass of debris drifts into shallower waters, the extended strands entangle on rocks and corals, ripping them from the surface and giving more heft to the net. Over the years, storms, shifts in currents, and the pull of tides allow the tangled mass to bulldoze a path to quiet waters where it comes to rest in what Brainard calls a "graveyard" of nets. Plastic lighters, fishing lures, and thousands of other pieces of plastic junk drift attached to squid and flying fish eggs in the ocean and catch the eye of albatrosses hoping to provide a nutrient-rich meal for their chicks at home on the islands. When fed, the chicks regurgitate the indigestible plastic meal.
"This scene repeats itself over and over and over again on every island we have visited," said Cousteau. "Some birdsparticularly Laysan and blackfooted albatross chickshave been affected and are found dead with all the plastic material visible in their stomach while the rest of their body decomposes. It is a sad and revolting scene every time."
Brainard said that even if debris were prevented from entering the ocean today, it would continue to circulate around the ocean for decades because it is so durable. "Plastics are miracle materials; they decompose very slowly in the marine environment," he said.
Appalled by the amount of debris on the coral reefs revealed by a survey in 1996, Brainard and his colleagues at NOAA and several other federal, state, and local government agencies, private companies, and conservation organizations launched a cleanup effort of the coral reefs in the Northwestern Hawaiian Islands.
To find the debris, divers are towed behind small boats, recording debris locations with global positioning system (GPS) technology. The divers then go down to the entangled mass of net on the reefs and cut it free in a painstaking and time consuming process to ensure that no further damage is caused.
"We could tie them to boats and jerk them off, but we know that would cause additional impact, so we physically cut them off strand by strand," said Brainard.
As the strands are cut free, the divers tie them to air bags that drift to the surface, preventing the strands from re-snagging on the reef. The debris is then lifted onto the small dive boats and transported to large vessels.
Through mapping and in-the-ocean experience, the crews have learned where the debris is more likely to accumulate, and as a result their efforts become more efficient each year. This season they have already collected 80 tons (176,000 pounds).
Brainard is unsure how much debris is left in the Northwestern Hawaiian Islands but said, "For every net removed, we know it has done something positive for the environment. It is one less net for a monk seal to entangle on, it is one less net for a turtle to entangle on, one less net to entangle coral. In that sense it is having a positive effect."
In the years ahead, the cleanup crew hopes to clear the hurdle of cleaning the reefs and employ remote sensing technologies to locate debris before it reaches the Northwestern Hawaiian Islands. Once located, they could ask vessels in the area to pick it up while it is still at sea and before it entangles monk seals and bulldozes coral reefs.
"The other thing to do is to prevent it from going into the ocean in the first place, but no one group has the control to do that," said Brainard. "It's been illegal for 25 years to put plastic into the ocean and it is still going into the ocean by one way or another."
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