Tsunami Debris Sparks Concerns Over Invasive Species

A large concrete dock that has recently arrived on a West Coast beach has sparked concerns about the introduction and spread of invasive species. The dock, which has been identified as coming from the port of Misawa on the northern tip of the main island of Japan, was dislodged following the earthquake and resulting tsunami in March 2011.

A very clear threat

What has biologists most concerned about the washed-up debris is the fact that many aquatic species native to Japan came along for the ride. As we know, once non-native plants and animals establish themselves in a new ecosystem, it can be disastrous to the native species.

“This is a very clear threat,” said John Chapman, a research scientist at Oregon State University’s Hatfield Marine Science Center in Newport, Ore., less than two kilometres south of Agate Beach, where the dock float washed up June 5.

Invasive species do great harm

The Great Lakes have been especially hard hit by non-native organisms. More than 140 of them, including plants, fish, algae, and molluscs, have become established in the Great Lakes since the 1800s. The impact has left some native fish and flora struggling for survival because non-native invaders often out-compete the indigenous species.

A whole new community

According to Chapman, the Japanese dock—150 tonnes of concrete and steel measuring 20 metres long, six metres wide, and two metres high—has provided a home for masses of aquatic organisms. “This is a whole, intact, very diverse community that floated across from Japan to here,” he said. “It’s almost certainly true that most of the things on this have not been introduced to this coast yet.”

Scientists are particularly concerned about a small crab found on the dock that has already spread along the East Coast as well as a species of algae that has already been found in Southern California. A starfish found on the dock, measuring about three inches across, is also thought to be new to our shores.

What they’re doing about it

For now, local authorities are cautioning looky lous to be careful around the washed-up dock. Though a radiation check came up negative, there is potential danger in climbing or poking around it, since tidal action makes the dock unstable.

In addition, harvesting any of the living organisms could allow the non-native species to make a foothold if some should be dislodged accidentally. Oregon state authorities are considering plans to scrape all the living things off the dock and bury them in the sand, so they won’t have an opportunity to spread, according to Chapman.