Mega-rafting ‘hitchhikers’ wash ashore
Debris from Japanese tsunami in 2011 delivers foreign species to B.C. beaches
More than 300 Japanese species — clinging to beams, furniture, boats and even entire docks — have washed up alive on the West Coast since the massive 2011 Tohoku earthquake and tsunami, according to a new study in the journal Science.
Now scientists wonder if we are sitting on an ecological time bomb.
Vessels and items that were in the water at the time of the tsunami are often teeming with oysters, barnacles, mussels and an assortment of mollusks, crustaceans and other Japanese marine species, even after a transpacific voyage.
About two and a half years after the tsunami, an 8.5-metre skiff covered completely with sea creatures washed up on Long Beach on the West Coast of Vancouver Island.
Large structures and boats have acted as “arks” for entire communities of sea creatures, a phenomenon dubbed “mega-rafting,” said the study’s lead author James Carlton, professor of marine sciences, emeritus at Williams College.
More than 300 potentially invasive “hitchhikers” have been identified on debris collected in California, Oregon, Washington, B.C. and Alaska, he said.
Twenty species have been identified in B.C., but that is likely a massive understatement, he said. At least 237 Japanese marine species were catalogued in Washington state and 278 in Oregon, but the west coast of Vancouver Island is relatively inaccessible, so no one is there to report it when bio-fouled items land.
“From what we have seen in news reports and from citizen scientists, we estimate that thousands of items arrived with living things attached and that a great many more species arrived,” he said.
There is no evidence yet that Japanese species are successfully colonizing B.C. waters.
“We are in a finger-drumming window of time between when a species arrives and when we can first detect (breeding) populations,” he said. “If that is happening in isolated locations, it’s very hard to see right now.”
Rafting events in which species survive over such massive distances are exceedingly rare, perhaps occurring once in 10,000 or 100,000 years, said Carlton.
“Until 2012, we had no mention in the marine science literature, policy literature or maritime history literature over 150 years of anything floating over from Asia and landing in North America with communities of Japanese species,” he said.
Scores of volunteers with the help of more than two dozen cooperating agencies from as far away as Japan have been scouring West Coast beaches and filling barges with debris since the massive quake, said Karla Robison, manager of environmental and emergency services for the District of Ucluelet.
After a formal request for assistance to the mayors of Tofino and Ucluelet from the consul general of Japan early in 2012, a 1,000-metre strip of beach was designated as a test site to monitor for debris.
At the time, millions of tonnes of wreckage were moving across the Pacific Ocean and there were concerns about radioactivity resulting from the meltdown at Fukushima nuclear complex.
The first creatures identified on the monitoring site were found on a post and beam that were confirmed to be Japanese by their unique joinery and dimensions.
Sleuthing for Japanese material and species is complicated by the fact that debris from other sources is also continuously washing up on our beaches, said Robison.
Inventories of the creatures they found and samples taken by the district and Parks Canada were sent to investigators led by Carlton.
After hearing about Ucluelet’s efforts to identify and recover Japanese tsunami debris, Carlton visited Robison in 2013 and delivered a crash course in marine species identification.