ENVIRONMENT

The Tohoku tsunami of 2011 caused longest maritime migration ever recorded, with crustaceans, sea slugs and worms riding 4,800 miles from Japan to the North American west coast. (The Guardian)

What was the Tohoku tsunami?

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit Text Set.

Discussion Ideas

• The “tsunami travelers” described in the Guardian article are associated with a tsunami that hit the Japanese east coast in 2011. What was the Tohoku tsunami? Read through our short article for some help.
  • The tsunami was a series of powerful waves triggered by the strongest earthquake in Japan’s recorded history—a 9.0 magnitude temblor. The earthquake struck below the North Pacific Ocean, 130 kilometers (81 miles) east of Sendai. Sendai is the largest city in Tohoku, the northeastern region on the island of Honshu. The Tohoku tsunami hit the coast of Japan with waves up to 40 meters (132 feet) tall.

 

• Waves associated with the Tohoku tsunami carried a million (!) sea creatures across the vast Pacific Ocean, from Japan to the West Coast of North America. What sort of creatures were “tsunami travelers”?
  • The new research reports 289 living invertebrate and fish species transported by the tsunami, “none of which were previously reported to have rafted transoceanically between continents.”
  • “Tsunami traveler” biota include:
    • macroinvertebrates. Most macroinvertebrate tsunami travelers fall into five groups: mollusks (sea slugs, oysters, barnacles, limpets, mussels); annelids (worms); cnidarians (jellies); bryozoans (filter feeders); and crustaceans (crabs, lobsters, shrimp).
    • fish. Cute Japanese barred knifejaw fish are tsunami travelers.
    • microinvertebrates. These microbes include plankton.
    • protists. More than 50 taxa of these weird microorganisms were identified as tsunami travelers.

 

• How did all those tsunami travelers actually travel? These are species that cannot migrate long distances.
  • It wasn’t natural. The species rafted on pieces of debris generated by the tsunami. The Tohoku tsunami “generated five million tonnes of debris from the three prefectures of Iwate, Miyagi, and Fukushima. About 70% sank quickly to the ocean floor, according to experts, but countless buoys, docks, boats and other items with buoyancy were swept out to sea.”
    • Here’s a key takeaway from Science: “Rafting, or the transport of organisms across water on natural debris such as trees or kelp, is thought to have contributed to the colonization of islands and the exchange of life between continents. [Learn more about that process here.] More recently, rafting on human artifacts, such as large plastic items, has been growing in importance; these items survive longer at sea than their natural counterparts and can therefore carry their cargo further. The scale and spatial extent of the rafting event associated with the 2011 tsunami are, however, unprecedented.”

 

• Are these tsunami travelers now invasive species in their new North American homes?
  • No. “For now, the team hasn’t detected any cases where Japanese species that were pushed over by the tsunami have established themselves in North American waters. But it’s too early to detect such invasions, says James Carlton, one of the researchers. They may be happening, but we wouldn’t know. And they’ll probably be a recurring feature of the future.”

 

TEACHERS TOOLKIT TEXT SET

The Guardian: Tsunami carried a million sea creatures from Japan to US west coast

The Atlantic: Japanese Animals Are Still Washing Up in America After The 2011 Tsunami

Science: Tsunami debris spells trouble

Nat Geo: Tohoku Earthquake and Tsunami

Nat Geo: Landslides Help Explain How Life Reaches Remote Islands

(extra credit!) Science: Tsunami-driven rafting: Transoceanic species dispersal and implications for marine biogeography