Almost 300 marine species hitched a ride on tsunami debris from Japan to the US

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On the morning of June 5th, 2012, John Chapman drove up to Agate Beach in Newport, Oregon, to take a look at a massive, 188-ton dock that had washed ashore during a storm. The dock was coated in seaweed and, to Chapman’s surprise, covered with small crabs, mussels, barnacles, and sea stars.

A tag revealed that the dock was from Misawa, Japan, a city that was hit by the mega tsunami that struck the area in 2011. After 15 months of drifting around the Pacific Ocean, the dock — and over 4,000 pounds of living marine creatures latched onto it — had landed in Oregon. “That was a stunning discovery,” Chapman, a professor of fisheries at Oregon State University, tells The Verge. “For my brain to accept what my eyes were seeing… I could not grasp that this could be true.”


The Misawa dock that landed in Agate Beach, Oregon, in 2012.
Photo: Oregon State University


The Japanese sea star Asterias amurensis found on the Misawa dock washed ashore in Oregon in 2012.
Photo by John Chapman

The dock, described in a study published today in Science, was just one of hundreds of pieces of tsunami debris that have arrived onto the beaches of Hawaii and the West Coast of the US, from Alaska to California. They represent the first massive example of how hundreds of marine species can drift for more than 4,300 miles across the ocean — and survive the trip. That’s because the dock and the other junk are made of plastic, cement, and fiberglass — artificial materials that last way longer than a piece of driftwood or seaweed. The new research reveals one more mechanism for species to migrate around the world, with potentially disastrous consequences.

Animals and plants introduced to new areas can harm local species — sometimes causing extinctions — and substantial economic damage. In Hawaii, for instance, species like plants and birds that have evolved in isolation for millions of years are being wiped out by invasive ones. The US Fish and Wildlife Service estimates that invasive species cost the US more than $120 billion in damages every year.


A piece of tsunami debris covered in marine organisms, retrieved in Oregon in 2013.
Photo: Hatfield Marine Science Center Oregon State University

Scientists have long known that marine species raft across big bodies of water. Genetic similarities between distant populations suggest that species must have crossed oceans somehow before, and there have been observations of species on rafts far out at sea, says Ceridwen Fraser, a senior lecturer at Fenner School of Environment and Society at Australian National University. Fraser, who wasn’t involved in the study published in Science, co-authored a 2010 study describing how several types of mollusks, crustaceans, and a sea spider from several subantarctic islands had hitched a ride on floating seaweed for a 310-mile trip to New Zealand that lasted several weeks.

Today’s study offers new and exciting evidence. “This is the first time that we are able to document rafting on such a massive scale,” says Martin Thiel, a professor of marine biology at Universidad Católica del Norte in Chile, who was not involved in the dock research. “We know that it has happened, but this is the first time we can see it basically in real time.”

On March 11th, 2011, after a magnitude 9 earthquake struck northeastern Japan, a massive tsunami with waves as high as 126 feet destroyed entire cities — killing over 20,000 people. When they receded, the waves dragged back with them millions of pieces of detritus. Chapman, and a team of other scientists, analyzed more than 600 pieces of tsunami debris — from vessels to crates to buoys — that were retrieved on US beaches beginning in 2012 all the way to last year. Through analyses and genetic tests, they identified 289 species of mollusks, crabs, sea stars, sponges, and even fish that survived the trek from Japan.


Japanese vessel that washed ashore in Oregon.
Photo: Oregon State University


Examples of tsunami debris brought in for inspection at Hatfield Marine Science Center at Oregon State University.
Photo by John Chapman

The species were able to survive for so long because — unlike hitchhiking animals thousands of years ago — their rafts were mostly made of non-biodegradable material, the authors say. “These species can survive for years if their raft, if their small boat is not dissolving under them,” says study co-author James Carlton, professor emeritus of marine sciences at Williams College. Because the researchers analyzed only a fraction of all the tsunami debris, many more species might have hitched a ride, Carlton says.

There’s no evidence that any of these species have become invasive in the US yet, but it’s “too early to make a call,” Carlton tells The Verge. It can take years for non-native species to establish themselves in an area, and it’s hard to predict which ones could be harmful until they actually become a problem, he says. Some of these species, however, have a history of being harmful invaders in other countries. A type of mussel called Mytilus galloprovincialis — the most common species found on the tsunami debris, according to Chapman — is known for reproducing quickly and displacing other mussels, in turn creating problems in South Africa.


Japanese buoy with Japanese oyster Crassostrea gigas found floating ashore of Alsea Bay, Oregon in 2012.
Photo by James Carlton

The study “uncovers a process that is wholly novel and entirely surprising,” says Steven Chown, a professor in the School of Biological Sciences at Monash University in Australia, who was not involved in the research. “It changes our worldview entirely about the way in which marine organisms may become invasive elsewhere,” he adds in an email to The Verge. But some researchers aren’t surprised by the study’s findings, and say that it reinforces what they’ve already understood. “We now know that rafting happens all the time,” Fraser writes in an email to The Verge, “but it is good example of the diversity of organisms that can be transported via this mechanism.”

The research suggests that plastic waste, which is ubiquitous in the ocean, can be more destructive to ecosystems than we’ve previously understood. “It’s more than turtles eating plastic bags and dying, it’s more than plastic occurring in most of our seafood,” Chapman says. “It’s that also it carries things around the ocean that then can become an economically severe problem.”

And this mass migration from Japan to the US might still continue. More tsunami debris is expected to reach the western coast this fall and next spring, Carlton says. It remains to be seen whether living marine creatures will be found attached to it — seven years after it was pulled out to sea. “We’re going to be watching what still comes in,” Carlton says. “This is not over.”



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