A dock that washed ashore in Oregon after being ripped out of a Japanese fishing port during last year’s tsunami could wreak havoc on West Coast marine life, the Associated Press reports.

Its 5,000-mile journey across the Pacific Ocean is troubling some scientists who told the AP that the dock is covered in organisms native to Japan. If those organisms thrive and spread, it could harm the ecosystem in Oregon and along neighboring shorelines.

A tiny species of crab, algae, kelp and starfish are among the hundreds of millions of organisms living on the dock, which is 165 tons of concrete and steel.

“This is a very clear threat,” said John Chapman, a research scientist at Oregon State University’s Hatfield Marine Science Center in Newport, Ore. “… It’s incredibly difficult to predict what will happen next.”

Volunteers in Oregon have removed the marine life from the dock since it washed up on a popular beach this week.

The dock is just a small portion of the 1.5 million tons of tsunami debris lost at sea, the AP reports. Scientists, however, predict that most of the debris will eventually end up in the Great Pacific Garbage Patch.

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