When a floating dock the size of a boxcar washed up on a sandy beach in Oregon, beachcombers got excited because it was the largest piece of debris from last year’s tsunami in Japan to show up on the US west coast.
However, scientists worried it represented a whole new way for invasive species of seaweeds, crabs and other marine organisms to break the Earth’s natural barriers and further muck up the west coast’s marine environments, and more invasive species could be hitching rides on tsunami debris expected to arrive in the weeks and months to come.
“We know extinctions occur with invasions,” said John Chapman, assistant professor of fisheries and invasive species specialist at Oregon State University’s Hatfield Marine Science Center. “This is like arrows shot into the dark. Some of them could hit a mark.”
Though the global economy has accelerated the process in recent decades by the sheer volume of ships, mostly from Asia, entering west coast ports, the marine invasion has been in full swing since 1869, when the transcontinental railroad brought the first shipment of east coast oysters packed in seaweed and mud to San Francisco, said Andrew Cohen, director of the Center for Research on Aquatic Bioinvasions in Richmond, California. For nearly a century before then, ships sailing up the coast carried barnacles and seaweeds.
Now, hot spots like San Francisco Bay amount to a “global zoo” of invasive species and perhaps 500 plants and animals from foreign shores have established in US marine waters, said James Carlton, professor of marine sciences at Williams College. They come mostly from ship hulls and the water ships take on as ballast, but also get dumped into bays from home aquariums.
The costs quickly mount into the untold billions of US dollars. Mitten crabs from China eat baby Dungeness crabs that are one of the region’s top commercial fisheries. Spartina, a ropey seaweed from Europe, chokes commercial oyster beds. Shellfish plug the cooling water intakes of power plants. Kelp and tiny shrimp-like creatures change the food web that fish, marine mammals and even humans depend on.
A 2004 study in the scientific journal Ecological Economic estimated 400 threatened and endangered species in the US are facing extinction because of pressures from invasive species.
It is too early for scientists to know how much Japanese tsunami debris may add to the invasive species already here.
“It may only introduce one thing,” Cohen said. “But if that thing turns out to be a big problem, we would rather it not happen. There could be an economic impact, an ecological impact or even a human health impact.”
The dock, torn loose from a fishing port on the northern tip of Japan, was covered with 1.5 tonnes of seaweed, mussels, barnacles and even a few starfish. Volunteers scraped it all off, buried it above the high water line, and sterilized the top and sides of the dock with torches.
However, there was no telling whether they might already have released spores or larvae that could establish a foothold in a bay or estuary as it floated along the coast, Carlton said.
“That’s the ‘Johnny Clamseed’ approach,” he said, referring to Johnny Appleseed, the pioneer US apple tree planter of the early 19th century. “While that is theoretical, we don’t actually know if that kind of thing happens.”