Invasive Species Carried by Floating Dock from Japanese Tsunami
On World Oceans Day, a study just published by Oregon State University's Hatfield Marine Science Center reminds us of the amazing power of oceans. The OSU marine biologists have been studying a 20-foot long concrete and metal dock that was pushed out of Japanese waters by the tragic tsunami which stuck last spring, and which has been pushed by ocean currents all the way to the coast of Oregon.
Survival "Mind-boggling"The dock throbs with life. Passers-by examining the huge piece of debris during a local news video of the floating dock can be overheard exclaiming, "look at the claws coming out on that one." OSU reports that biologists have already collected "4-6 species of barnacles, starfish, urchins, anemones, amphipods, worms, mussels, limpets, snails, solitary tunicates and algae" from the dock.
John Chapman, an OSU marine invasive species specialist, called the survival of so many species during the long trip on the open ocean "mind-boggling." The discovery forces a re-assessment of assumptions about the ability of many species to survive the harsh conditions of the vast expanses of blue:
Life on the open ocean, while drifting, may be more gentle for these organisms than we initially suspected. Invertebrates can survive for months without food and the most abundant algae species may not have had the normal compliment of herbivores. Still, it is surprising.
The floating dock toured at least 5500 miles (8850 km) of ocean from the port of Misawa, in northern Japan's Aomori Prefecture, to Agate beach in Newport, Oregon, approximately 100 miles southwest of Portland.
Tons of Organisms on World Tour?Initial press releases published an estimate of 100 tons of organisms on the dock. The OSU official information mentions only a figure of 13 pounds of critters per square foot, presumably indicating that the 100 ton estimate has been retracted. By our calculations, assuming that the 13 lbs./sq. ft. figure implies surface area, a dock of 20 feet long by approximately 10 feet wide and 8 feet high would have something more in the neighborhood of ten tons of hitch-hiking organisms aboard if you assume that surface area is increased by some hollowness in the underside of the structure.
But the total mass of species arriving on US shores is of little importance. Because these critters are alive, any of them that have hopped off into local waters and find themselves feeling quite at home there could thrive and multiply. In fact, because these are the organisms that have survived an arduous journey, they could be particularly robust examples of their species, more likely to be able to stake a place in their new habitats.
The brown algae covering most of the dock was identified as wakame (Undaria pinnatifida) by OSU marine ecologist Jessica Miller, an assessment confirmed by OSU phycologist Gayle Hansen. Brown algae, native to the western Pacific, has already invaded some areas of southern California, so the threat is real.
The examination of the dock, and tons of tsunami debris arriving on foreign shores, by scientists well informed in the methods of detecting and deterring invasive species will help to prevent the worst possible imbalances from arising. But the fight against invasive species in the oceans of our well-travelled, small planet remains a challenge that only increases in severity as the ocean itself carries its denizens across the globe, hitch-hiking on human debris.