Rafting Across the Pacific: Invasive Species Coming to North America with Debris from the Japan Tsunami.


Home / Rafting Across the Pacific: Invasive Species Coming to North America with Debris from the Japan Tsunami.

Tsunami debris include invasive species. Photograph by U.S. Navy.

The earthquake and tsunami that devastated Japan in March of 2011 loosened many millions of tons of material from the land and cast them into the sea. While most quickly sank, the rest are riding the Kuroshio Current across the Pacific Ocean, and outriders have already reached North America. So far, there haven’t been any problems with radioactivity (most people’s first concern), but potentially invasive species have come along for the ride.

Plants and animals have been drifting around on ocean currents for thousands of years. The seeds of some tropical plants can make spectacular journeys—they’re called sea beans. Mary’s Beans (Merremia discoidesperma), seeds of a rare tropical vine found in Mexico and Central America, have made it all the way to Europe. Their common name comes from religious Europeans who drew their own conclusions about the cross-shape on the seeds, back in the Middle Ages.

Birds and animals, needing food and water, can’t survive as long as plant seeds, so usually don’t travel as far. Yet this is presumably how at least a few animals colonized some ocean islands, perhaps most famously the Galapogos Islands off South America.

Japan Tsunami: Marine Debris

Of course, there’s already a lot of debris floating around the ocean, possibly even carrying invasive species: seaweed, algae, and other small marine species. NOAA’s Marine Debris Monitoring Program was set up to track this debris; most is garbage washed into the ocean from the land.

The Japan tsunami debris is mostly more of the same. But it also contains some floating docks, boats, and small appliances that can transport small marine species quite comfortably across the Pacific. In early June 2012, part of just such a dock arrived on a State Park Beach in Oregon. It was nearly 70 ft long, and had been torn from a fishing port in Japan. Invasive species were found on it: seaweed, plankton and small crabs.

Docking at the Olympic National Park

On December 18, a large dock was found on a remote beach in the Olympic National Park, within the Olympic Coast National Marine Sanctuary – a designated wilderness area. The dock is 65 ft long, 20 ft wide, 7.5 ft tall, weighs about 185 tons, and is made of Styrofoam within steel reinforced concrete. The concrete is damaged, exposing both rebar and the Styrofoam, which could be eaten by fish, birds, and marine mammals.

While the tide was out, staff from government agencies hiked along old logging roads and wind-swept beaches to take samples of attached marine life attached to the dock. When the tide is in, waves wash the dock and dislodge this marine life back into the ocean. Any invasive species could devastate the intertidal zone of the Olympic Coast National Marine Sanctuary, which is the most diverse coastal ecosystem on the west coast.

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