They’re a long way from home.

Nearly 300 different species of fish, mussels, crabs and various other sea creatures drifted from the shores of Japan to the Pacific Coast of the United States on debris sent across the ocean by a tsunami in 2011.

“When we first saw species from Japan arriving in Oregon, we were shocked,” John Chapman from Oregon State University told BBC News.We never thought they could live that long, under such harsh conditions.”

Chapman co-wrote a study published Thursday in the journal Science that explored the sea critters’ journey to the United States after the Tōhoku earthquake triggered the tsunami. These catastrophic events sent debris, such as docks and coolers, drifting across the ocean.

People began noticing these objects washing ashore five years ago. In 2012, for example, a 66-foot-long dock washed up on Oregon’s Agate Beach, and it was covered in small sea creatures, the Oregonian reported.

Now, 289 species have been identified in the study.

“It’s a bit of what we call ecological roulette,” lead author James Carlton, a marine sciences professor at Williams College, told the Associated Press.

Since much of the debris was made of plastic that wasn’t biodegradable, it continued to float with the sea creatures hanging on. They somehow survived the 4,300 mile trip, some cycling through several generations.

“These species can survive for years if their raft, if their small boat is not dissolving under them,” Carlton told the Verge.

Because of this, “many hundreds of thousands of individuals were transported and arrived in North America and the Hawaiian islands — most of those species were never before on our radar as being transported across the ocean on marine debris,” Carlton told BBC News.

In essence, the tsunami debris made it possible for sea creatures to migrate around the world, which many of the species were previously unable to do.

“We have created a new ecological process, the process of mega-rafting,” Steven L. Chown, a professor of biology at Monash University in Australia, who was not involved in the report, told the New York Times. “The development of materials that can float for ages, and the rising levels of seas due to climate change, make the possibility of these events larger and larger.”

For now, it isn’t an issue — but invasive species do come with a high price tag. The U.S. Fish and Wildlife service estimates that they cause more than $120 billion in damages each year in the United States.

The prospect makes some nervous.

“We have loaded the coastal zones of the world with massive amounts of plastic and materials that are not biodegradable,” Carlton told the New York Times. “All it takes is something to push this into the ocean for the next invasion of species to happen.”

For now, though, many in the scientific community are simply in awe.

“The fact that communities of organisms survived out in the open ocean for long time periods (years in some cases) is amazing,” James Byers, a marine ecologist at the University of Georgia in Athens, wrote in an email to the Associated Press.

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