U.S. Navy photo by Mass Communication Specialist 3rd Class Dylan McCord/Released

Residents and visitors of a popular beach in the US State of Oregon were stunned when a massive rectangular dock float washed up on shore last week.

The float turned out to be one of four from the fishing town of Misawa, Japan, which were pulled out to sea during last year’s tsunami. Another float washed up on a nearby island, while the other two have not been found.

The dock was covered in hundreds of millions of flora and fauna, native to Japanese waters, but strangers to the Pacific Coast of the United States. The structure is home to kelp, mussels, algae, barnacles and other life forms, and is causing some concern among scientists who fear for the ecological balance of the region.

A research scientist is quoted by the Associated Press:

This is a very clear threat […] This is a whole intact very diverse community that floated across from Japan to here. That doesn’t happen with a log or a thrown-out tire. I’ve never seen anything like this.

–John Chapman, Oregon State University’s Hatfield Marine Science Center

But ships larger than the dock float have routinely traveled between the US and Japan for over 100 years, so what’s the big deal?

Part of the concern seems to be economic.

From the Guardian:

The costs quickly mount into the untold billions of dollars. Mitten crabs from China eat baby Dungeness crabs that are one of the region’s top commercial fisheries. Spartina, a ropey seaweed from Europe, chokes commercial oyster beds. Shellfish plug the cooling water intakes of power plants. Kelps and tiny shrimp-like creatures change the food web that fish, marine mammals and even humans depend on.

The problem is if even one problematic species from Japan’s tsunami debris takes hold in local ecosystems, but what’s the role of a bunch of (normally small) debris when compared to the giant tankers and ships that arrive every day from around the world?

For another story on how the debris is being monitored in Hawaii, click on this link to see a video report from KITV.