Nearly 300 aquatic species have landed on American shores since the 2011 Japanese tsunami by hitching rides on manmade debris, according to a team of researchers from Portland State University and other institutions.
Their findings about long-distance life rafting on debris and its impact on the environment were published in the Sept. 29 issue of the journal Science.
The tsunami offered the research team a rare opportunity to observe the phenomenon, which until this point was rarely studied or quantified.
The 2011 tsunami from a 9.0 magnitude earthquake off the coast of Japan caused millions of objects, ranging in size from small plastic fragments to fishing vessels and large docks, to be carried out to sea. The debris was picked up by marine currents, and much of it landed in places such as Hawaii, Alaska, the Pacific Northwest and Northern California. The landings occurred throughout a five-year period studied by scientists from the joint PSU-SERC (Smithsonian Environmental Research Center) Aquatic Bioinvasions Research and Policy Institute, one of seven entities involved in the study.
“Some of the species – including Japanese seastars, shore crabs and barnacles -- are known to be invasive in other parts of the world, but until this point had never reached the West Coast of the United States,” said PSU-SERC researcher Brian Steves.
Invasive species have the power to multiply quickly, take over the habitats of native species and cause environmental damage.
“This event provided the opportunity to track and evaluate the fate (destination and species composition) of the biologically rich debris field over multiple years from a single known time and place of origin,” the article states.
The researchers said they were surprised that living species from Japan are continuing to arrive on the West Coast after six years at sea. One reason, they said, is the prevalence of plastics, which do not biodegrade and can persist in the oceans for decades, providing a secure vehicle for mollusks, crustaceans and other life.
“As humans continue to place more plastic objects along the coasts and into the oceans, the potential for rafting events like this also increases,” Steves said.
Contact John Kirkland at jrk3@pdx.edu