How the Tohoku tsunami transported Japanese marine life to the American coast

Study reveals 2011 tsunami displaced marine life from Japanese coast to American coast via oceanic debris

On March 11 2011, a 9.1 magnitude earthquake hit the Pacific coast of Tohoku, Japan. To say that it was powerful would be an understatement, with the then Japanese Prime Minister Naoto Kan saying that “in the 65 years after the end of World War II, this is the toughest and most difficult crisis for Japan”. The earthquake triggered tsunami waves that were up to 133 feet tall, damaging many establishments in the country from roads and railways to buildings and dams. Six years later, the people of Tohoku are still reeling from the damages caused by the catastrophe.

 

However, the consequences of the earthquake are not only evident in the damages that it has caused in the Japanese archipelago and its surrounding area. In a report published by the American Association for the Advancement of Science, it has been found that the tsunami waves have caused Japanese marine life to be displaced by over 7,000 kilometres to faraway Hawaiian, American, and Canadian coastlines. According to the researchers, this was “an extraordinary transoceanic biological rafting event with no known historical precedent”. They studied 635 debris objects made from non-biodegradable materials such as fibreglass and polystyrene foam. Within these objects, they found that 289 Japanese species have successfully established a colony. 80 of these species were found on a 170 ton section of dock. Most of the debris was considered “high-richness arrivals” meaning that they carried with and in them more than 20 Japanese species.

 

The Japanese invertebrate and fish species come from 16 phyla, and they began landing on American and Canadian coastlines in 2011. Some of the marine life displaced includes molluscs, limpid, crabs, other crustaceans, and even some fish such as chordate. They are shown to have had very successful reproduction along the way. According to the researchers, this was made possible by the slow movement of the debris, as the speed of the debris only ranged from two to four kilometres per hour. As well as this, the materials’ non-biodegradability contributed to the species’ survival. Organic material like trees and root masses have short lives at sea, however, non-biodegradable materials survive at sea for longer. The result is that the species had the time not only to adapt to the changing conditions across the Pacific oceans, but to also establish a colony.

 

Researchers have warned that the non-biodegradable debris has possibly brought with it invasive species that may destroy existing ecosystems in the places in which they have landed. It is easy to see that the amount of non-biodegradable waste was key to these species’ survival, and as world population increases, so will the waste present in our waters. If this phenomenon continues, it can lead to detrimental change on our coastlines and less diversity in seashores across the globe.

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