Almost 300 marine species have rafted at least 4,350 miles across the Pacific from Japan to the US on plastic wreckage left by the 2011 tsunami, according to new research.
The coastal creatures include crabs, mussels, barnacles, sponges and sea stars. They provide the first direct evidence of animals hitch hiking huge distances on a vast scale.
And the phenomenon is likely to be common with many non native species travelling thousands of miles on chunks of plastic and other ocean garbage.
Animals and plants introduced to new areas can harm local fauna and flora, sometimes causing extinctions. And climate change is making the problem worse.
In Hawaii, where some of the new animals have arrived, plants and birds that have evolved in isolation for millions of years are being wiped out by invasive ones.
Artificial materials - which also include cement and fibreglass - last much longer in water than a piece of driftwood or seaweed.
The study published in Science reveals one more way for species to migrate around the world, with potentially disastrous consequences.
Marine biologist Dr Greg Ruiz, of the Smithsonian Environmental Research Centre, Maryland, said: “I didn’t think most of these coastal organisms could survive at sea for long periods of time.
“But in many ways they just haven’t had much opportunity in the past. Now, plastic can combine with tsunami and storm events to create that opportunity on a large scale.”
The 2011 tsunami triggered by a magnitude nine earthquake created a wave of up to 126 feet.
It swept millions of objects out to sea from small pieces of plastic to entire fishing boats - and even docks.
One188-ton dock washed ashore at Oregon during a storm the following year. It had a tag that revealed it was from Misawa - a city in Japan that had been hit by the huge wave that killed more than 20,000 people.
It was coated in seaweed - and over 4,000lbs of living marine creatures such as small crabs and mussels.
Marine scientist Professor John Chapman, of Oregon State University, said: “This has turned out to be one of the biggest, unplanned, natural experiments in marine biology, perhaps in history.”
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