Vocabulary: seaside 词汇：海边，海滨

Staff on Oregon beach burying marine organisms from Japan which washed up recently. Photograph courtesy of Oregon Parks and Recreation (OPRD).

It's not every day that you find a motorcycle or a concrete dock washed ashore, but that's what people on the West coast of the United States have been spotting. These items were among debris from the March 2011 tsunami in Japan.

It's been estimated that 1.5 million tonnes of debris is floating through the North Pacific Ocean and new items are frequently dragged up onto sandy beaches.

Volunteer beachcombers have been working at Yaquina Bay in Oregon to clean the beach of all rubbish. The group - college students, pensioners, surfers and locals - work alongside State Park officers and is given gloves to protect their hands. There's been no evidence yet of any radioactive debris, but they are all too aware of the meltdown at the Fukushima nuclear plant after the tsunami.

The arrival of alien species is another cause for concern in the US. The concrete dock that drifted in to Newport, Oregon, was found to contain sea creatures originating from Japan that could threaten the local ecosystem. Some starfish prey on native marine organisms and the Wakame kelp is known as one of the worst invasive species outside its natural environment.

As the Hatfield Marine Science Centre's John Chapman explained on the International Business Times website: "In sheltered waters, the Wakame kelp can quickly form large beds that block out sunlight essential for the survival of native kelps, seaweeds, and other marine algae."

The debris is also a reminder of the human suffering brought by the tsunami that killed more than 15,000 people.

Jack Barth, a professor at Oregon State University's College of Oceanic Atmospheric Sciences, points out that some personal items found can provide some closure for families in Japan.

Sixteen-year-old Misaki Murakami, a tsunami survivor, was reunited with his football after it washed up in Alaska. His signature on the ball made it possible to trace him.

Murakami said: "I'm very grateful as I've so far found nothing that I'd owned."