Tohoku tsunami debris, some with invasive life, still turning up on North American West Coast

by

Kyodo

When debris from the March 2011 earthquake and tsunami disaster in northeast Japan first wended its over through the Pacific Ocean’s currents, concerns about potential radioactive contaminants from the Fukushima No. 1 nuclear plant disaster briefly gripped residents of Hawaii and North America’s West Coast.

Fewer paid attention to the living things, such as mussels, barnacles and seaweeds, that clung to the debris, and their capacity to harm marine ecosystems unaccustomed to their presence.

Five years later, debris is still washing up, and scientists have begun to explore whether the invasive species have become established in North America.

“Although there’s a lot of marine debris out there, we generally don’t know when it began its ocean life and we often don’t know where it came from,” said Jim Carlton, professor emeritus at Williams College in Massachusetts and lead principal investigator in a U.S.-Japan project to evaluate species on the debris.

“For the first time in the history of marine biology, we have an injection into the ocean of a massive amount of anthropogenic material, from a known source, at a known time,” Carlton said.

Hundreds of species, some never found before in North America, have survived on the debris, which has included floating docks, a ship, many small boats and large numbers of buoys, floats and crates.

Prior to the tsunami it would have been “extraordinarily rare” to find an object with living Japanese species on the Pacific coast of North America or in Hawaii, Carlton said.

Samuel Chan, an expert in aquatic invasive species and aquatic ecosystem health at the Oregon Sea Grant program at Oregon State University, said it was previously thought unlikely organisms from Japan’s coasts could survive multiyear journeys across the Pacific due to a relative lack of nutrients and plankton in the open ocean.

Chan said the sheer volume of the debris reflects how industrial infrastructure has rapidly built up along coastlines in modern times.

“A similar tsunami 300 years ago, or even 60 years ago, would not have created as much marine debris that became a vehicle for species that can become invasive across the Pacific,” Chan said.

Debris has been found between San Francisco and southern Alaska, as well as Hawaii, with the coasts of Oregon and Washington reporting the highest numbers of objects.

Jonathan Geller of Moss Landing Marine Laboratories in California’s Monterey Bay is analyzing the genetics of Japanese species found on the debris.

Unlike organisms carried in the ballast water of ocean-going ships, which tend to be in the larval or juvenile stages of their life cycles, the tsunami debris carries adults that may be better able to establish populations, Geller said.

Japanese mussels, barnacles and seaweeds have all been found, and could threaten their North American native counterparts either by competing with them or by spreading parasites or pathogens.

“About 5 percent of (mussels) on the tsunami debris carry a parasite that can impact juvenile mussels and oysters and pose a threat to aquaculture on the North American West Coast,” Geller said.

Several of the hitchhikers are on the list of the world’s worst invasive species, said Cathryn Clarke Murray, visiting scientist at the North Pacific Marine Science Organization near Vancouver, British Columbia.

These include brown kelp, known as wakame in Japan, where it is a prized product of the tsunami-hit Sanriku coast, and the carpet sea squirt, which forms blanket-like colonies that smother the sea floor.

In 2015, scientists studying tsunami debris began surveys of organisms along the affected coasts, looking for any new species and testing their genomes against those of species in Japan.

Once a species is introduced, there is often a “lag time” of three to five years before the invading population grows to a size that can be noticed, Carlton added.

Carlton said a network of 55 taxonomists in the United States, Canada, Japan and Australia is currently on the case.

The effort is supported by a network including government officials, rangers, citizen scientists and beach cleanup teams.

“If something large turns up we usually hear about it within 12 to 24 hours,” Carlton said.

Disasters aside, globalization has seen rapid changes in the potential for invasive species to cross the world’s oceans, whether unintentionally carried on ships or ordered alive on the Internet.

“The ability to move any species around the world in 24 hours has no precedent in recent history,” Carlton said.

“Tsunami debris may well still be turning up on coasts in 2021, and whether or not there will be living Japanese species aboard I don’t know — but some of these species can live 10 or 15 years, and a fiberglass boat takes a long time to dissolve.”

Still out there are two of four floating docks wrenched from the port of Misawa, Aomori Prefecture. One of the docks came ashore in Oregon in June 2012 and another in Washington in December that year.

A third dock was spotted off Hawaii in September 2012 by a fishing boat that followed it for several days.

Carlton said it is hard to say when or where the third and fourth Misawa docks will turn up, but “they’re not sinkable.” He takes his passport wherever he goes, in anticipation of a phone call promising to add another piece to the tsunami debris puzzle.