By Yoko Inoue | Daily Yomiuri
Debris dragged out to sea by last year’s tsunami has started to arrive on the other side of the Pacific Ocean, bringing unfamiliar creatures as well as concerns that invasive species will threaten ecosystems on the West Coast of the United States.
Although some tsunami wreckage has already arrived, local scientists are concerned that much larger quantities of debris will begin reaching the western shores of North America this autumn.
A huge floating pier from Aomori Prefecture beached itself on the coast of Oregon in early June, bringing with it many species of marine life native to Japan. The roughly 20-meter-long pier was swept away by the tsunami from fishing port of Misawa, Aomori Prefecture, and arrived on a beach near Newport more than one year later.
Locals who flocked to see the unexpected arrival were shocked not only by the immense size of the pier but also by the many species that had hitched a ride, which included wakame seaweed, sea chestnuts, crabs, sea anemones, starfish and oysters.
In total, scientists from Oregon State University’s Hatfield Marine Science Center counted more than 90 species. U.S. scientists had anticipated the arrival of a certain amount of debris from Japan, but the diversity and sheer number of marine creatures on the pier far exceeded expectations.
Among the new arrivals from Japan, wakame seaweed and the crab species are highly reproductive, more so than Oregon’s indigenous varieties, and are considered invasive species that could have a major impact on local ecosystems. Locals tried to destroy all the specimens on the pier with blowtorches and other means.
Oregon State University Assistant Prof. Samuel Chan, an expert on marine ecosystems, said the high quality of the pier’s construction allowed such a large number of creatures to survive inside for 15 months.
Chan said if the pier had entered a nearby bay, its environmental impact could have been severe. Since bays are closed water systems largely unaffected by sea currents, wakame and other seaweed species could have easily established themselves, posing a considerable threat to domestic U.S. seaweeds.
However, the debris that has already reached U.S. shores is only a tiny fraction of the total. The Environment Ministry believes about 1.5 million tons of debris were dragged out to sea by the March 11, 2011, tsunami.
The full-scale arrival of broken houses and other large pieces of debris on U.S. shores is expected to begin in autumn. The ministry has calculated that about 41,300 tons will arrive by sometime in February, meaning that U.S. communities are probably far from finished with unwelcome Japanese sea life.
The Oregon State scientists have asked people who find debris with marine life adhered to it to bury it in sand or somehow prevent the creatures from surviving to harm local ecosystems. Predicting the arrival of tsunami debris is quite difficult, as the journey from Japan is influenced by ocean currents, weather and geographical formations.
With local governments in the United States struggling to grasp how to handle the debris, nongovernmental organizations from Japan and the United States held a conference in Oregon in August to discuss cooperation on the issue.
According to Tokyo-based Japan Environmental Action Network, U.S. attendees requested information on what kind of debris could arrive and other details. Other U.S. participants expressed interest in using the monitoring cameras that have been installed on the coast in several places in Japan to watch for approaching debris.
Allowing tsunami wreckage to sit untouched after arriving on U.S. shores makes it easier for foreign species to establish themselves.
The cameras are part of a test project run by the Environment Ministry, and are currently operating in 10 locations around the country, including remote islands such as the Tsushima Islands in Nagasaki Prefecture and the coastline of Hokkaido. Images are analyzed to determine the amount of floating plastic waste and are used by the National Institute for Land and Infrastructure Management.
“It’s hard to understand what’s going on with ocean debris because it sometimes comes ashore in places that are hard for people to reach,” said Hirofumi Hinata, chief of the institute’s Coastal Zone Systems Division. “Cameras like this could also be helpful along the coast of North America.”