After Japan's devastating 2011 tsunami, the receding waters pulled countless pieces of debris into the Pacific Ocean. That flotsam became "rafts" for endemic Japanese species on an unexpected 7,000-kilometer voyage.
Image: Getty Images/AFP/T. Kitamura
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Researchers have recorded 289 separate species which they say survived the trip from Japan to Hawaii or the US West coast.
Among those species were fish, mussels, snails, worms, crabs and algae. Some of them survived up to six years at sea. Many reproduced during the voyage.
The species were discovered on more than 600 separate "objects" surveyed on the US Pacific coast by a team led by James Carlton of Williams College.
The objects included anything from small pieces of plastic to entire ships and even structures from harbors and marinas, such as a dock that washed up on the coast of the US state of Oregon.
How did they get there? Once the tsunami's waters had pulled these objects into the ocean, currents sent them along on a subsequent journey of 7,000 kilometers or more.
One of the participating researchers, John Chapman from Oregon State University, described a sense of "shock" upon seeing so many species survive the journey - but also worry.
"The crustaceans and bivalves are of particular concern because they could introduce new diseases, and compete with, displace or otherwise affect our oyster or mussel populations," he has said of the new arrivals.
Not a one-off event
At this point it remains unclear whether any of the Japanese species have found permanent homes in their new marine environments in the US. Such a process could already be underway but would take decades to document.
Species are still arriving, but most are now doing so on pieces of plastic. That's because wooden "floats," which decompose rapidly on open ocean waters, stopped arriving after 2014.
Still, are such events limited to the kind of mega-tsunamis that occur after earthquakes of 9+ on the Richter scale?
The scientists suspect two factors will increase these cross-oceanic transfers of species in the coming years.
The first is the increasing accumulation of plastic "transporters" in our oceans. Ten million tons of plastic reach the ocean yearly, with the number expected to rise in the near future.
The second is due to climate change, which is expected increase the strength - and possibly the frequency - of extreme weather events, like hurricanes or tropical storms. These storms are capable of pushing local species into open waters, where the current takes them away.
The article was published in the US journal "Science."
When Mother Nature gets angry, really angry
On average, some 10,000 people die in earthquakes around the world annually. The temblors have often provoked tsunamis and wider devastation. DW takes a look at some of the most powerful earthquakes of the last century.
Image: Getty Images/AFP/J. Barret
Most powerful earthquake ever recorded
The most powerful earthquake ever recorded hit Chile's coast in May 1960. The quake, 9.5 on the Richter scale, lasted almost 10 minutes, resulting in massive infrastructure damage. Around 5,700 people were killed in Chile while the resulting tsunami left 130 people dead in Japan and another 61 in Hawaii. This picture shows the remains of Corral harbor in Chile's Valdivia province.
Image: Getty Images/AFP
Good Friday earthquake
The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, remains the strongest earthquake to hit the US to date. It occured on Good Friday, March 27, across south-central Alaska. The quake and the following tsunamis caused about 139 deaths. The picture above is from a small fishing village on Kodiak Island and it shows debris from houses and boats.
Image: Getty Images/Central Press
Most powerful earthquake ever recorded in Japan
A team member from Japan's Rescue Dog Association and his dog search for victims. Northeastern Japan was struck by a devastating earthquake, measuring 9.1 on the moment magnitude scale, followed by a massive tsunami. The natural disasters claimed almost 18,500 lives, and crippled the Fukushima nuclear power plant, in what is considered the world's worst nuclear power disaster since Chernobyl.
Image: Getty Images/AFP/Y. Chiba
2004 Indian Ocean earthquake
The undersea megathrust earthquake, magnitude 9.1, triggered a series of devastating tsunamis, killing some 280,000 people in 14 different countries and inundating coastal communities with waves up to a 100 feet. It was one of the deadliest natural disasters in recorded history.
Image: Getty Images/P.M. Bonafede/U.S. Navy
Kamchatka earthquake
A megathrust earthquake occurred off the coast of Kamchatka Peninsula in eastern Russia on November 4, 1952. The 9.0 magnitude quake caused a tsunami leading to widespread destruction and loss of life around the Kamchatka peninsula and the Kuril Islands. More than 2,300 people were killed.
2010 Chile earthquake
An 8.8 magnitude earthquake occurred off the coast of central Chile in February 2010. It triggered a tsunami which devastated several coastal towns in south-central Chile and damaged the port at Talcahuano. The quake and the following tsunami resulted in the deaths of around 450 people, while damage to the local fisheries' business was estimated at 66.7 million US dollars.
Image: Getty Images/AFP/M. Bernetti
China 1976 quake
An abandoned railway coach in Tangshan, China after an earthquake devastated the industrial town on July 28, 1976. The quake, measured at 7.4, struck near the industrial city in northeastern Hebei province. The official death toll is given as 242,000 but is believed to be significantly higher. Some estimates put the deathtoll at around 500,000.
Image: Getty Images/Keystone/Hulton Archive
1920 Haiyuan earthquake
The earthquake, measured at 8.3, occurred in the Haiyuan county of the northern province of Ningxia and caused aftershocks for almost three years. As a result, up to 235,000 people died immediately. Many more, who were living in camps due to the continuing aftershocks, perished later due to severe winter conditions.
Image: Getty Images/AFP
2010 Haiti earthquake
A man walks amid the rubble of a destroyed building in Port-au-Prince following the devastating earthquake that rocked Haiti on January 12, 2010. With a magnitude of 7.0, the quake destroyed thousands of buildings and left at least 200,000 people dead.
