Five years after a massive earthquake struck Japan and
triggered a tsunami that is still washing debris onto the West Coast of the
United States, scientists are unsure whether any of the 200-plus non-native
species that hitchhiked over on that debris have gained a foothold in Northwest
Four separate findings of barred knifejaws (Oplegnathus
fasciatus) – a fish native to Japan – have been reported over the past three
years, and Mediterranean blue mussels have been ubiquitous on tsunami debris.
Yet no populations of non-native species that arrived with the tsunami debris
are known to have established reproductive populations.
“Maybe we dodged the bullet, although it is still too early
to tell,” said John Chapman, an Oregon State University invasive species expert
who has investigated tsunami debris along the Pacific coastline. “It is
possible that we have not yet discovered these reproductive populations, or
that some species from Japan may be cross-breeding with our own species.”
Scientists have not had adequate resources to look
extensively up and down the Pacific coast for evidence of establishment by
non-native species – especially along long stretches of rugged shoreline.
The magnitude-9 earthquake that struck Japan on March 11,
2011, was the largest in that country’s history and generated a tsunami that
had waves estimated as high as 133 feet. The power of these two events,
combined with the growth of human settlement over the past two to three
centuries, created a new paradigm, said Samuel Chan, an expert in aquatic
ecosystem health and invasive species with the Oregon Sea Grant program at
“A tsunami 300 years ago, or even just 60 years ago, would
not have created as much marine debris that became a vehicle for moving species
across the Pacific Ocean that could become invasive,” Chan said. “What makes
these major tsunami-driven events different in modern times is the substantial
human industrial infrastructure that we have built along the Pacific coast.”
The first indication that a potential problem loomed came in
June of 2012, when a large concrete dock that originated in Misawa, Japan,
washed ashore near Newport, Oregon – just a stone’s throw from OSU’s Hatfield
Marine Science Center.
The 165-ton dock – which was 66 feet long, 19 feet wide and
seven feet high – was covered with nearly 200 species of plant and animal life,
including a species of brown algae (Undaria pinnatifida) that nearly covered
the structure. Chapman and colleague Jessica Miller also found Northern Pacific
sea stars, Japanese shore crabs, at least eight species of mollusk, an anemone,
a sponge, an oyster, a solitary tunicate, three or more species of amphipods,
four or more species of barnacles and worms, bryozoans, a European blue mussel
known as Mytilus galloprovincialis, and a sea urchin.
“Frankly,” Chapman said, “we were blown away. We had always
thought these organisms would not be able to survive the long trip across the
Pacific Ocean, the middle of which is a biological desert. Yet here they were.”
In March of 2013, a boat from Japan containing five barred
knifejaws washed ashore in the state of Washington; one is still on display in
the Seaside Aquarium. A second knifejaw was filmed in a shipwreck near
Monterey, California. Then a third knifejaw was found trapped in a crab pot
near Port Orford, Oregon, in February 2015. Just two months later, another was
discovered in a boat tank from Japanese tsunami debris near Seal Rock, Oregon.
“Those knifejaws all survived,” Chapman said.
“Theoretically, the water temperatures north of Point Conception, California,
are too cold for them to spawn. But it’s hard to know for sure.”
Chan has been working with colleagues from Japan’s Tottori
University for Environmental Studies on a project that launched dozens of
transponders into the waters off that country and traced their path across the
Pacific Ocean to North America. The researchers’ goal is to find out what
routes the tsunami debris might have taken and how that may influence the type
of organisms found aboard the debris.
“Some species have been discovered that are not native to
Japan, and others have not even been identified,” Chan noted. “The transponders
bobbed around off Japan for some time and then went fairly quickly across the
Pacific. But once they arrived here, they moved in and out of near-shore
waters, and up and down the coast.
“Satellite tracking of transponders and their discovery by
beachcombers indicates that they floated for 2-3 years before they beached on
land,” Chan added. “The movement patterns of the transponders within the
continental shelves of Japan and North American – where nutrients and food are
relatively available – could be one piece of a complex puzzle that have allowed
these organisms to survive the trans-Pacific journey.”
Chan said international exchanges in the five years since
the Tohoku earthquake and tsunami have been a bright point, resulting in close
collaboration and a shared sense of discovery among Japanese and American
“The debris still arriving five years later is a reminder
that has raised awareness among people – many of whom have been complacent or
unaware – about the power and destruction that earthquakes and tsunamis can
cause on both sides of the Pacific,” Chan said.