U.S. biologists concerned with unwelcome stowaways on Japan tsunami debris

5:51 AM, Jun 14, 2012   |    comments
Japan tsunami debris washes ashore in America.
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Docks, boats and other debris from Japan's 2011 tsunami drifting onto West Coast beaches represent a trash cleanup challenge that may last for years to come.

Biologists are equally worried about the threat from invasive species attached to the debris. How big a threat remains to be seen. Biologists fear that foreign species that arrive on our shores - crabs, barnacles, starfish, snails and plants - could establish a foothold and crowd out native creatures and plants.

There's precedent for the concerns: The European green crab wrecked the soft-shell clam industry in New England and Nova Scotia in the 1950s. Zebra and quagga mussels clog water intake pipes, filtration and electric power plants across the Midwest to the tune of $1 billion in annual cleanup costs. Shipworms, small-shelled clams that burrow into wood, established themselves in San Francisco Bay. They bore into piers, docks and boats and cause $200 million in yearly damage.

So concern over the 66-foot-long concrete and plastic foam dock that landed last week on a beach near Newport, Ore., last week, makes sense. The dock carried dozens of foreign species, which surprised researchers by surviving more than 15 months of travel across the deep ocean. Oregon park officials rounded up 1.5 tons of marine life critters aboard the dock and buried them in an 8-foot-deep hole above the high-tide mark June 7.

Oregon officials are weighing bids to demolish the structure in place or tow it out to sea for disposal.

"The dock is just the tip of the iceberg, but we don't know how big an iceberg," says marine invasive species expert James Carlton of Williams College maritime studies program at the Mystic (Conn.) Seaport.

Most of the debris washed offshore in the tsunami sank, according to Japanese estimates, but roughly 1.5 million tons of it remains afloat in the Pacific. "The tsunami was without precedent, so we are bound to get some more surprises," Carlton says.

Triggered by a magnitude-9.0 earthquake, the tsunami and subsequent waves that then retreated to the sea trapped debris in Pacific currents, says Keeley Belva of the National Oceanic and Atmospheric Administration. "Part of the problem has been identifying what debris truly comes from Japan and what is the sort of trash - a gum wrapper - that might have fallen from a boat. We need solid identification."

Though cargo ships constantly arrive at West Coast ports from Japan, they don't pose the invasive species threat that a dock trailing oysters, algae and other creatures does, says marine ecologist James Morris of the NOAA National Centers for Coastal Ocean Science in Beaufort, N.C. "Attempts are made to prevent hitchhikers in the shipping trade," Morris says, such as scraping barnacles off hulls or dumping contaminated ballast water at sea. Trash from cargo ships that regularly washes ashore is covered with deep-sea organisms, which, unlike species attached to the tsunami debris, are unlikely to survive in coastal bays and harbors.

San Francisco Bay has become a hot spot for hundreds of invasive pests, from Japanese goby fish to Black Sea jellyfish. A 2005 Cornell University report put the damage cost of invasive aquatic species at more than $6.6 billion a year, everything from carp that worsen water quality by eating plants that clean the water and stirring up mud to crabs that prey on oyster farms.

"Many times, the effects of invasive species are not realized until many years after their introduction," when they have reproduced many times over, Morris says.

The real danger comes from Japanese debris carrying invasive crabs or other species drifting into a harbor or Puget Sound's salt marshes where they may gain a foothold, Carlton says. "We may have gotten lucky," he says. "That isn't a location where the harbor species on the dock can survive." On the other hand, he says, "more is coming."

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