Invasive species, stowed away on tsunami trash, show up off the West Coast

Japan is still recovering from the massive 2011 tsunami that struck in the wake of a 9.0 earthquake, and it turns out that the West Coast of the U.S. is still experiencing some of the fallout as well, as dozens of marine species show up here after a long journey across the Pacific Ocean.

The millions of tons of debris the tsunami sucked into the ocean became homes to hundreds of different species of marine life, at least 289 of which traveled more than 4,500 miles to the West Coast, according to a new study published in the journal Science.

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"We documented some of the farthest distance, longest-lasting marine dispersal events probably recorded," said Jessica Miller, study co-author and associate professor at Oregon State University's Department of Fisheries and Wildlife.

Researchers from Washington to California and as far off as Hawaii have been documenting the arrival of non-indigenous species on debris from Japan since the first major piece was spotted in Oregon in June 2012: a dock with more than 100 different creatures aboard.

"That really put the idea that there could be a lot of different species being transported long distances on our radar," Miller said.

Everything from small pieces of plastic to crates, buoys and fishing boats have been languishing in the Pacific for the past six years. Ocean currents and storms eventually push them and their tiny passengers towards their final destinations.

Stowaways have included shrimp, fish, barnacles, mussels, oysters, sea anemone, sea stars, crabs and algae, some of which are known invasive species.

A Japanese buoy covered in oysters (Crassostrea gigas) was found floating in Alsea Bay, Oregon in 2012.

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James T. Carlton

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The Japanese shore crab, for instance, has invaded the Atlantic coast of the U.S. It was found on a vessel that arrived from Japan. The Japanese sea star and skeleton shrimp, which showed up off of the West Coast, have invaded ecosystems around the globe, including Australia.

So far there's no indication that any of these creatures have established themselves in the U.S., Miller said. However, experts say it can take a decade or more to see the effects of an invasive species on a habitat.

The movement of species from one place to another is nothing new, but Miller said it's rare for so many species to migrate so far in such a relatively short period of time.

Usually marine life uses kelp or pumice, and sometimes even trees, as natural rafts to get from one place to the next. However, the debris from Japan are made of plastic or metal, materials with much longer staying power.

"In this case that created these incredibly long lasting rafts that were able to carry sort of whole communities of coastal invertebrates, and a couple of fish across the ocean," Miller said. It's a demonstration of what's possible when man-made materials make their way into bodies of water and act as vessels to transport creatures. It's possible that we'll see more of these events as more disasters occur and litter the ocean with debris, she said.

"It's an interesting example of how our impact has changed a natural event," said Miller.

Miller said that researchers have seen a decrease in the amount of debris showing up on U.S. shores over the years, but that they're covered in the same amount of marine life that they always were. It's unclear how much longer refuse will continue to come in, as researchers are unsure of exactly how much is still floating out in the middle of the Pacific.