Japanese Tsunami Sends Invasive Debris and Marine Algae to the US Pacific Northwest Coast

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In a new article published in Phycologia, researchers detail the collection, examination and classification of the foreign marine algae from the Japanese tsunami of 2011 to determine whether it posed an invasive threat to the North American coastline. Their findings provide insight into the global impact of tsunamis.

Phycologia Volume 57 Issue 6 cover

Phycologia Volume 57 Issue 6

Many of the items were fouled with a wide variety of healthy Japanese species and the potential invasion of Northeast Pacific shores by these species seemed highly probable.

Phycologia – In March 2011, the Great Tohoku Earthquake and Tsunami devastated the Pacific Coast of Japan; however, the tsunami also had global implications. When the water from the 40-m waves that pounded the coastline finally receded, a lot of debris from the island was carried out to sea. This debris, ranging from beach docks to boats to small flotation devices, started washing up on the shores of the Pacific Northwest in the United States in 2012, bringing with it fouling foreign marine algae that posed a major invasive threat to the US coastline.
In the current issue of Phycologia, researchers from Oregon State University, United States, and Kobe University, Japan, detail the collection, examination and classification of these foreign marine algae from their first appearance in 2012 through 2016 when the debris appeared to have subsided. The main goal of the research was to assess the algae and determine whether it posed an invasive threat to the North American coastline.

As the debris settled on beaches, the researchers, with the enlisted help of state workers, volunteers and other scientists, worked to collect samples of the attached algae. Overall, more than 500 samples were collected from 42 pieces of debris. Once collected and delivered, the samples were immediately examined and cataloged. Each sample was meticulously evaluated for the following characteristics: taxonomy, life history (including longevity and successional type), global distribution, size, how many times it appeared on different debris, at-sea survival and Northeast Pacific occurrence both pre- and post-tsunami.

The researchers identified 84 species and varieties of algae and cyanobacteria from the debris. They noted that 83% were reproductive, 48% were ephemeral and 75% were opportunistic. This led them to conclude that many species had high colonization potential upon reaching the shores of the Pacific Northwest. They also found that 72% of the species were globally widespread. Not all species survived the more than 4-year study. The short-term survivors appeared to be the larger species, whereas the long-term survivors were the smaller species, and tended to be the species with the highest invasive potential.

The researchers’ findings indicate that if not dealt with immediately, the risk of colonization was extremely high from the foreign debris. Dr. Gayle Hansen, a researcher in this study, stated, “Many of the items were fouled with a wide variety of healthy Japanese species and the potential invasion of Northeast Pacific shores by these species seemed highly probable. From 2012 to 2016, we studied the algae arriving on debris and discovered 84 species, ranging from large kelp to small filamentous forms. A surprisingly large number of these species were reproductive (83%), a feature that increased both their survival on debris and also their colonization risk. Realizing the invasion threat, the government agencies and volunteers in these two states immediately began removing the fouled debris from the beaches. With a subsidy from the Japanese Ministry of the Environment, the cleanup efforts were remarkably extensive. This alone appears to have prevented many invasions, and even today, no new algal colonizations have been found that can be directly linked to tsunami debris.”

The researchers concluded that due to the swift cleanup efforts, no foreign species was able to colonize upon reaching US shores. However, this study proves the global impacts of a tsunami. Once debris is swept out to sea, the foreign species of marine algae that are attached have a high probability of colonization when they finally wash ashore, if not handled immediately.
Full text of the article, “Invasion threat of benthic marine algae arriving on Japanese tsunami marine debris in Oregon and Washington, USA,” Phycologia, Vol. 57, No. 6, 2018, is available at http://www.phycologia.org/doi/full/10.2216/18-58.1

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Dominique Scanlan
Allen Press
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