Mediterranean mussels, acorn barnacles and anemones crossed the Pacific on this buoy found in Long Beach, Washington, in February 2017. (Photo: Nancy Treneman)
by Kristen Minogue
On March 11, 2011, a 125-foot tsunami struck Japan’s Tōhoku coast, triggered by a massive earthquake just hours earlier. The cost in human life and property damage was devastating. When it receded, it set in motion another chain of events—one scientists are still watching unfold eight years later. It’s a story of millions of pieces of plastic that journeyed across the ocean, and the plants and animals that rafted with them.
A year after the tsunami, beach walkers in Oregon and Washington began spotting pieces of debris with Japanese characters. When scientists came on the scene, they confirmed much of the debris had come from the Tōhoku region in the wake of the tsunami. Even more stunning, many were covered in shellfish, barnacles and other creatures that survived the ocean crossing. In 2017, scientists reported nearly 300 living species had rafted to the Hawaiian Islands or the North American West Coast on tsunami debris, and more animals were still arriving through summer 2018.
But that wasn’t the end. After surviving an ocean voyage, a new question emerged: Can these species survive in their new homes?
Pioneers on Plastic Rafts
Christina Simkanin, a marine biologist with the Smithsonian Environmental Research Center (SERC), is part of a team of scientists trying to predict which species stand the best chance. Their findings appeared in a new study, published Monday in Global Ecology and Biogeography.
Christina Simkanin, marine ecologist at SERC, studies how aquatic plants and animals move around the globe.
“The tsunami debris basically showed that coastal species can make it for years in the open ocean, which is super weird,” she said. In the past, biologists thought such a long, slow voyage would kill most coastal creatures, either from lack of food, ultraviolet exposure, or saltier water. But once they’ve landed, there are plenty of barriers to setting up shop.
Simkanin and biologists from Williams College – Mystic Seaport and Fisheries and Oceans Canada zeroed in on one of the biggest: how hospitable the environment is. If temperature, saltiness and other conditions don’t match, a species might not survive long enough to establish a population.
Jim Carlton, marine ecologist at Williams College, has been studying species on tsunami debris since it first began washing up on the West Coast. (Photo: Anna Sawin)
The team looked at 48 species that made it all the way across the Pacific. All told, 70 percent stood a fighting chance. After building a model and crunching the data, the team discovered 13 species had landed in areas with a perfect environmental match. Another 21 species didn’t match the exact location where they landed, but could well have landed somewhere else suitable on the Pacific coast, given that debris washed ashore from southeast Alaska to central California.
Many of those species are completely new to North America’s West Coast. But even species that aren’t new could pose a threat. One concern is that if a tsunami-borne invader finds a population of its own species already on the West Coast, it could up the genetic diversity pool. That could make invaders more resilient, more adaptable, and better able to spread.
“Greater genetic diversity often comes along with greater ability to survive,” Simkanin said.
Slideshow: Meet The Contenders
These 10 species—some new to the West Coast; some already present—are among the tsunami rafters with a decent chance of survival somewhere on the West Coast. Hover over the images to learn more about them as you click through the slides.
Of course, environmental matching isn’t the only obstacle new arrivals must surmount. There’s no shortage of ways for species to fail.
“Things as simple as wave action can take you out,” said co-author Jim Carlton, an emeritus ecologist at Williams College who co-authored the first 2017 paper on Japanese tsunami species. Predators and competition pose additional threats. “There are lots of ways between cup and lip, as it were, to not make it.”
Landing on sandy beaches, Simkanin pointed out, can also be a problem. Many species that latched onto tsunami debris need a hard surface to settle on. A dock or rocky shore is their best bet. And for animals that reproduce sexually, there’s the age-old need to find a mate.
But even with these barriers, plenty of species still find a foothold.
Stemming the Plastic Tide
This leaves environmental managers with the dilemma of what to do. When it comes to invasive species, the prevailing wisdom is that an ounce of prevention is worth a pound of cure. But preventing tsunamis and other natural disasters is all but impossible. And unlike more predictable ways invasive species get moved around—like shipping—floating debris can land just about anywhere.
Barring prevention, early detection is the next best thing, according to Simkanin. That’s something models like the one in the new study can help with.
“Eradication is possible when populations are small,” Simkanin said. “It becomes much harder when nonnative populations become large. So catching an invasion early is really important.”
A watchful public is crucial, Carlton said. Locals are often the first to notice something new in their homes. “We need the eyes and ears of the public to be out there looking for novel invaders….There’s vastly more members of the public that are on the coast than there are scientists.”
Meanwhile, large patches of ocean plastic continue to grow. This could make mass rafting events more common, according to the study’s authors, even without extremes like tsunamis. Carlton and a team of Smithsonian scientists are studying samples from the Great Pacific Garbage Patch, one of the largest swaths of ocean-borne debris and microplastics. Perhaps the keys to stopping future invasions—and ultimately kicking our plastic addiction—lie buried somewhere in the miles of drifting trash.
