Newsweek International - - NEWS - BY MEGHAN BARTELS @meghan­bar­tels

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any other day for the many mus­sels along Japan’s eastern coast­line—cling­ing to docks and strain­ing their snacks out of the wa­ter—un­til 2:46 p.m., that is, when two col­lid­ing chunks of the Earth’s crust set off six min­utes of ground-shat­ter­ing quakes, then a se­ries of gi­gan­tic waves pow­er­ful enough to crush three-story build­ings and rip docks off their moor­ings.

That earth­quake and tsunami killed about 18,000 peo­ple and caused more than $200 bil­lion in dam­age. Sim­ply clear­ing away the de­bris took about four years. But not all of the de­bris stayed in Japan, and the un­told story of what was sent adrift of­fers a re­veal­ing glimpse of how nat­u­ral dis­as­ters re­shape the world, of­ten in the most un­ex­pected ways.

The tsunami marked the mo­ment when thou­sands of those mus­sels set off on an in­cred­i­ble ad­ven­ture across the Pa­cific Ocean.

In the past six years, de­bris from Japan has landed on the beaches of Hawaii and all along the west­ern coast of North Amer­ica. And ac­cord­ing to a study of the tsunami’s af­ter­math pub­lished Septem­ber 29 in Sci­ence,a small sam­ple of that de­bris—much of it plas­tic—brought with it liv­ing spec­i­mens of al­most 300 species.

The re­port of­fers a “min­i­mum pic­ture” of the tsunami wreck­age trans­ported to North Amer­ica, says James Carl­ton, lead au­thor on the project and a ma­rine ecol­o­gist at Williams Col­lege. And the de­bris is still ar­riv­ing, he re­ports. “We had no idea it would last un­til 2017 and be­yond.”

The long trail of de­bris means hun­dreds of species got a foothold in new ecosys­tems. Sci­en­tists have known for a long time that species hitch rides on logs, but it’s in­cred­i­bly dif­fi­cult to track a piece of de­bris from take­off to land­ing. “This is re­ally the first largescale [mi­gra­tion] event that we are ba­si­cally wit­ness­ing as it un­folds,” says Mar­tin Thiel, an ecol­o­gist who stud­ies species move­ment at the Catholic Univer­sity of the North in Chile and wasn’t in­volved with the study. ”

Ecol­o­gists could track most of the tsunami de­bris be­cause it was rel­a­tively easy to iden­tify. In many cases, an en­tire dock or boat washed ashore, com­plete with reg­is­tra­tion num­bers or other iden­ti­fy­ing in­for­ma­tion.

For the study, the team ex­am­ined 634 pieces of de­bris be­lieved to stem

Most “de­bris hitch­hik­ers” won’t sur­vive, but lucky ones could be­come an in­va­sive species.

from the tsunami, then tal­lied the an­i­mals each piece was car­ry­ing, aided by 80 sci­en­tists from around the globe. The fi­nal tally: liv­ing crit­ters from 289 species, in­clud­ing Ja­panese skele­ton shrimp, Pa­cific seastar and barred knife­jaw fish.

Some of those crea­tures may not have made the whole jour­ney—they may be de­scen­dants born on the voy­age—but they all have the chance to live in a new habi­tat. And the re­searchers es­ti­mate that many more liv­ing or­gan­isms have the same op­por­tu­nity, given the large amount of un­stud­ied de­bris in the oceans. Most of these “de­bris hitch­hik­ers” won’t sur­vive be­cause they didn’t hap­pen to be de­posited in a habi­tat that suits them, but any that do get lucky could be­come an in­va­sive species, able to thrive so well that na­tive species suf­fer.

There’s no telling which species might do that kind of harm—carl­ton com­pares the process to “eco­log­i­cal roulette,” be­cause pre­dict­ing which new ar­rivals will not meet nat­u­ral preda­tors in a new lo­ca­tion is im­pos­si­ble. The past can be in­for­ma­tive, how­ever—mediter­ranean mus­sels, one of the 289 species found in the de­bris, have in­vaded other places—so sci­en­tists are mon­i­tor­ing coastal habi­tats in Hawaii and North Amer­ica for early signs of an in­va­sion.

The amount and va­ri­ety of de­bris still wash­ing ashore six years af­ter the Ja­panese tsunami is stag­ger­ing. Nat­u­ral de­bris like wood pe­tered out af­ter the first few years, since it of­ten breaks down en route. But the plas­tic keeps com­ing. “We have ba­si­cally a huge ar­mada of plas­tics, and those are the ones that have been mak­ing it along this very long trip,” Thiel says.

Tsunami de­bris is just a frac­tion of all the plas­tic in Earth’s oceans, so the same odysseys be­ing doc­u­mented here could be more com­mon than we re­al­ize. “We know that plas­tic in the ocean is not a good thing for many dif­fer­ent rea­sons, and this is one of the rea­sons,” Thiel adds. He’s re­fer­ring to ugly sur­prises, like the Ja­panese or­ange-spot­ted sea anemones that came ashore from south­ern Ore­gon to cen­tral Cal­i­for­nia dur­ing the spring of 2016, the first time the anemone was spot­ted on any tsunami de­bris.

“The tsunami event was this ob­vi­ously hu­man tragedy,” says Cathryn Clarke Mur­ray, a ma­rine ecol­o­gist at the North Pa­cific Ma­rine Sci­ence Or­ga­ni­za­tion in Bri­tish Columbia, which has been sup­port­ing Carl­ton’s re­search and other projects study­ing the im­pact of tsunami de­bris. But, she says, the study has pro­vided new in­sights into how species move around the world. “It re­ally changed our per­cep­tion of coastal ecol­ogy.”

Carl­ton and Thiel both note that the study is timely, given the paths of Hur­ri­canes Irma and Maria across Florida and the Caribbean, knock­ing plas­tic and other de­bris into the ocean. Many species could eas­ily have hitched a ride to travel along the Gulf Stream and even­tu­ally land in Europe. And if cur­rent trends con­tinue, more and more of that de­bris will be long-float­ing plas­tic. That’s wel­come news for ac­ci­den­tal ad­ven­tur­ers, since no one wants to be stranded in the mid­dle of an ocean. There’s no telling, how­ever, how these wan­der­ers will be greeted once they make land­fall.

CRUISE, NO CON­TROL Some of the de­bris cre­ated by an earth­quake and tsunami in Japan drifted across the Pa­cific (in­clud­ing a barge that made land in Long Beach, Cal­i­for­nia), bring­ing with it many ac­ci­den­tal tourists.

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