Recently, contractors hauled away the final piece of a concrete dock weighing more than 165 tons that washed up on an Oregon beach after a 14-month journey across the Pacific Ocean. The dock was one of four that broke loose from the Japanese fishing port of Misawa during last year’s tsunami. One dock was found in Japan, a second turned up in Oregon in early June, and two are still missing.

The largest tsunami-borne object to travel across the Pacific and wash up on the West Coast so far, the dock generated immediate interest from the public. More than 1,000 people a day visited the site to pose for photos and be part of history. An enterprising artist even painted a breaking wave along one of the dock’s massive seven-foot-high sides.

Scientists at Oregon State University have been studying the impacts of invasive marine species for decades. But when the Misawa dock showed up about five miles down the coast from their Hatfield Marine Science Center, what they found defied their expectations. The Misawa dock was covered with hitchhikers: two tons of marine life – algae, crabs, shrimp, mussels, sea stars and more.

Essentially a floating island, the dock carried a complete ecosystem of Japanese coastal species, transported more than 5,000 miles across the Pacific Ocean. Scientists identified nearly 100 different species of sea life on the dock, including a number of species—like the brown kelp Undaria, the Asian shore crab and the North Pacific sea star—that are known to pose especially high ecological risks when introduced to new territories.

Globally, invasive species are a big deal. They can wreck havoc on natural ecosystems by out-competing native species, introducing disease, and leading to costly removal efforts. Case in point: When the Misawa dock landed on the beach, state workers launched an immediate emergency response, scraping the dock and burying everything removed, torching the dock to kill any remaining living organisms, and cutting the concrete up and hauling it to a landfill. All that took two months. And the final tab was an estimated $84,000.

Many are wondering if more tsunami debris items might show up soon bearing unwanted visitors. Only time will tell. But beyond the biology lesson, this dock has also become a fitting emblem for the enduring strength of the Japanese people. Workers at the salvage company saved one concrete chunk from the landfill. This piece of the dock will become part of a tsunami memorial to be installed in the Hatfield Marine Science Center – a fitting tribute to the human and biological impacts of the tsunami.