SCIENCE -- June 27, 2012 at 12:00 PM EDT
Invaders Hitch a Ride on Tsunami Debris
"If you take nothing else from this lecture -- a tsunami is a flooding hazard," said Eddie Bernard, and then he repeated it: "It's a flooding hazard."
Bernard, director of NOAA's Pacific Marine Environmental Laboratory and longtime tsunami expert, was featured speaker for the 2012 Revelle Lecture at Smithsonian's Museum of Natural History this March, and he was showing aerial videos of the tsunami that struck the northeastern shore of Japan on March 11, 2011.
The footage showed the startling speed at which the water pushing unrelentingly inland, along the way uprooting houses, trucks and ships filled with diesel fuel.
"These houses are being lifted up by the buoyancy of the water and then advected by the forward motion of the tsunami," he explained, "and everything in its path becomes part of the water mass, so we're no longer dealing with just the fluid, but water plus all this other debris."
This becomes a very toxic environment, he continued, "not only because if you're in it, all the material that could crush you, but also because of all of the hazardous material that gets in there."
Now, a year later, much of that debris is washing up along the western coast of the United States, carrying unwanted organisms with it.
The slide show below documents some of that debris, including this: a 66-foot long, 165-ton dock made of reinforced concrete with a Styrofoam core that landed on the shore of Agate Beach on June 5.
"We were absolutely not expecting anything like this," said David Solomon, safety and risk manager for Oregon State Parks and Recreation. "It's amazing that it got here at all, and that it got here as fast as it did."
After the 2011 tsunami struck, an estimated 5 million tons of debris washed out into the ocean. A month later, NOAA researchers had tracked a debris field the size of California. Since then, beachcombers have waited for the tide of tsunami refuse to wash up on the western shores of North America. And it's been trickling steadily onto shore, and will continue, experts estimate, for the next few years.
Most of it resembles any other garbage and refuse floating in the Pacific Ocean -- plastic bottles, Styrofoam containers, crates and fishing accoutrements- which are hard to trace back to a specific place and event.
These Northern Pacific sea stars, a highly invasive species from Asia, were found aboard the dock. Courtesy: Oregon State University Hatfield Marine Science Center
But in other cases, there is little doubt about its origin. For example, one plaque contains Japanese writing that lists the dock's manufacturer, which the Japanese consulate in Oregon traced to Aomori Prefecture, north of the earthquake's epicenter. The prefecture confirmed it was one of four piers ripped loose during the tsunami.
It was covered with plants and animals from Japanese waters, which were alive and healthy after their travel, said John Chapman of Oregon State University's Hatfield Marine Science Center. To his knowledge, no species has ever before crossed shore-to-shore on debris after a disaster, he said. And many of the estimated 50 species aboard were invasive, posing threats to marine life along the western coast.
"We want to study it and collect it, but at the end of the day our response was 'kill, kill, kill,'" Chapman said.
Other ships have spotted ocean debris laden with Japanese organisms like the ones on the dock, including a few of what Chapman called "super baddies." Organisms like Northern Pacific sea stars have been found in Tasmanian waters, along with a seaweed called "wakame," used in miso soup, which California waters have been trying to get rid of for years. No one knows how they survived the trip intact.
"This has never happened before," Chapman said. "And this is just the beginning. There's going to be a lot more than this."
In March, we posted this story, which shows a model and a map developed by NOAA to track debris circulating in the Pacific Ocean. NOAA also launched a marine debris tracker app, which people can use to log rubble they find along coastlines and in waterways.
Scientists are now on the lookout for more large debris carrying invasive colonies of Japanese species along the Oregon shore. Chapman said this is a scientific boon for invasive species ecologists, who can study the shells of the dock crabs and mussels for the answer to their unlikely survival.
Volunteers and staff have shoveled, scraped and blow-torched 1.5 tons of foreign marine plants, barnacles, starfish, crabs, algae and mussels, according to Solomon.
The dock is not salvageable, even though it arrived relatively intact. And during the week following its arrival, it drew some 10,000 visitors to the beach, Solomon estimated. He said that while the dock is unusual, it should serve as a reminder that tons of debris washes up on the West Coast every year.
The dock may still carry invasive species, so Oregon State Parks and Recreation will dismantle and remove it from the beach. And parts of the dock will be preserved for a memorial to the victims of the tsunami. Chapman supports that idea.
"I'm climbing on this huge, twisted thing...and there's the serious sense that people died here," Chapman said. "This isn't just a dock."