What Happens When Tsunami Wreckage Floats Across the Pacific and Lands in America?

The state of the universe.
Aug. 15 2013 12:02 PM

The Tiniest Tsunami Refugees

They came from Japan, clinging to wreckage. They made it to the U.S., only to be destroyed. They are crabs, sea stars, and kelp.

(Continued from Page 1)

Life is always on the move. A new species establishes in San Francisco Bay about every 14 weeks; even more modest Yaquina Bay, Ore., which has significantly less ship traffic, gets a new member every year. Species stow away in ballast water, or attach themselves to vessel bottoms, reliably thwarting quarantine efforts. Biological communities everywhere are constantly being poked, prodded, and tested, as new species look to take advantage of even the slightest openings and opportunities. Species that might seem innocuous, like a humble shore crab barely an inch and a half wide, can have significant impacts on the ecosystems that receive them.

But the Misawa docks, and the tsunami debris more generally, are something different. They are, for Chapman, objects of ambivalence. On the one hand they make him nervous, loaded as they are with potential and known invaders; and ecologists have a bad track record of predicting what species will invade where, so of course it is right and proper that their hangers-on were destroyed as quickly and thoroughly as possible. But the docks are also exciting. They approximate a phenomenon that has been happening for millions of years, one that most scientists never expected to witness in their lifetimes. They blur the conceptual line between what biologists call invasion, and colonization.  

A closeup of the biota found on Misawa 1.
A close-up of the biota found on Misawa 1

Photo courtesy Oregon State University's Hatfield Marine Science Center.

“Ocean-scale rafting is a sort of fundamental tenant of marine biogeography,” says Jim Carlton, a biologist at Williams College who has examined the docks with Chapman, and is working with a group of scientists to study tsunami debris. Rafting, for instance, is how Hawaii has its own species of land snails, at least for now. It is how Madagascar has lemurs. (It may also be how cholera eventually reaches the U.S.) But such events are rare; species need to establish only every few hundred thousand years to account for the biodiversity seen on island chains. “I personally have watched the West Coast for 40 years looking exactly for this, for something that crossed the ocean with something arriving alive from the other side,” Carlton says.

The Misawa docks are exactly that sort of event. Even as Misawa 1 and Misawa 3 were blowtorched and scraped clean as quickly as possible, most of the organisms on them got away. On Misawa 1, Chapman thinks more than 60 percent of everything escaped; on Misawa 3, isolated and battered for days before anyone could reach it, the percentage of escapees is sure to be higher. Not all of them will survive, of course. Sometimes, though, all it takes is one.

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The docks, therefore, could be thought of as the largest experiment in invasion ecology ever run. What happens when you take four large durable structures, all from the same place (and so with the same species on them), and set them adrift? How long will they take to reach the other side of the ocean? What will survive? What will they pick up? And what if they don’t make the crossing at the same time? What will the resulting communities look like?

Chapman, Carlton, and a host of other invasion ecologists are getting their answers now, and will be for the next several years. Less than 1 percent of that anticipated 1.5 million metric tons has arrived. What remains will show up in waves, depending both on prevailing winds, which drive downwelling and upwelling on the West Coast (i.e., pushing debris towards shore, or drawing it away), as well as the properties of the debris itself. This year most of what has washed up has been smaller, more buoyant, and also more anonymous. At one point a lot of lumber turned up on the beach. Chapman could walk along Agate Beach and see, about every 100 meters or so, a large piece of treated timber that he knew was from Japan. But who really looks that closely at logs?

And so Chapman has an eye out for larger things. Last September, between the landings of Misawa 1 and Misawa 3, he learned that a second dock (Misawa 2) had been spotted off the coast of Hawaii, 30 miles from Maui. It would swing within 15 miles of Molokai before observers lost sight of it as the currents carried it back out to the open ocean. The fourth dock, Misawa 4, has yet to be seen. They are out there somewhere, among a debris field that, according to NOAA estimates, is now spread out across an area roughly three times the size of the United States. Caught in the great gyres of the Pacific, each dock bides its time with its own patient passengers, all of them in search of a new home.

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