Rafting on a Tragedy

In March of 2011, the magnitude 9.0 Tohoku earthquake occurred off the coast of Japan setting a record for the strongest earthquake for Japan and the 4th strongest in the world. Indeed, the quake actually moved parts of Japan nearest its epicenter up to 13 feet closer to North America. The earthquake caused a subsequent tsunami which hit the coast of Honshu, ravaged 200 miles of land, and reached a maximum wave height of nearly 40 meters in the Iwate prefecture. Over 20,000 deaths occurred during and after the earthquake and tsunami and an estimated 210 billion dollars (USD) in damage was done.

5 million tons of debris was washed out to sea.

Where did it all go? Nobody knows for sure, but we do have models. The first models in 2011 were extremely basic and did not account much for changing winds or different types of objects. Shortly after the tsunami, Ocean Drift Models from the International Pacific Research Center (IPRC) were used to predict debris trajectories based on satellite-tracked buoys and satellite-measured winds. Today, advanced models’ predictions of where the debris will travel has matched with the locations where various pieces of debris have appeared.

IPRC’s 15 year projection model of the Japanese tsunami debris field under zero windage. Source

IPRC’s 15 year projection model of the Japanese tsunami debris field under zero windage. Source

A Tale of Four Docks

Originating from the Misawa Fishing Port in Japan, four enormous, indestructible docks were ripped from their hinges during the tsunami’s drawback and taken out to sea. While all four are exactly alike and came from exactly the same location, their trajectories were not exactly the same. Misawa 1 was found on Agate Beach in Oregon. Misawa 3 was found in Washington’s Olympic Coast National Marine Sanctuary. Misawa 2 was spotted off the coast of Hawaii, but never beached and has not been spotted since. Misawa 4 has never been seen. Each of these docks is 66 ft long, 19 ft wide, 7 ft tall, and weighs approximately 185 tons.

A simplified illustration of dock trajectory.

A simplified illustration of dock trajectory.

A member of the team that hiked to the remote location Misawa 3 landed in Olympic National Park, Washington. Source

A member of the team that hiked to the remote location Misawa 3 landed in Olympic National Park, Washington. Source

Out of roughly 1.5 million tons of debris still floating around the Pacific (the other 3.5 is said to have sunk), it is a wonder that we have encountered 3 out of the 4 largest and most dangerous structures. Though the landing of Misawa 1 came as a relief at first, its interception in June 2012 was when we realized not only that we would be seeing what is now called Japanese Tsunami Marine Debris (JTMD), but also that Japanese organisms were surviving the conditions of the open ocean for months and years. Many of them had even resumed reproduction upon arrival in more familiar coastal conditions. Approximately 100 species, weighing around 2 tons in total, were still alive when scientists arrived to sample Misawa 1. Misawa 3 had substantially less: about 29 species. Suddenly this debris was no longer just an annoyance for cities, beach cleaners, and owners of private beaches or an increased hazard to birds and marine animals; it was an opportunity to observe a phenomenon never before studied in great detail: rafting.

Something Wicked This Way Comes

The Pacific gyres and garbage patches. Source

The Pacific gyres and garbage patches. Source

Rafting is the process whereby organisms float from one place to another on an object over a body of water. While some marine creatures are capable of creating their own raft (e.g., Portuguese man o’ war), others will raft on buoyant objects that they were already living on or that they settle on out in open waters (e.g., pelagic gooseneck barnacles). We know rafting happens, as evidenced by anecdotal observations (see Thiel and Gutow 2005) and studies of pumice rafting after a major volcanic event (Bryan et al. 2012). In fact, rafting might well be one of the most important modes of dispersal of non-native species in addition to vectors such as ballast water and intentional introduction by humans. So why is rafting not studied more in depth? Certainly there is enough trash out there. But the issue isn’t the abundance of trash, it’s knowing from where and when the object(s) originated.

The 2011 Japanese tsunami was a disaster of epic proportions, but out of this tragedy, scientists can gain valuable insight about this method of transportation. Objects that appear on the coast of Hawaii and the West coast of America and Canada can be identified as Japanese based on what the object is, how it’s made, what it’s made with, and/or by Japanese characters that are still legible (specifically for Misawa docks and boats/skiffs).

Sightings of floating debris began in September 2011, but was not reported to start washing ashore until June 2012. Some interesting things have been seen or washed ashore, including a motorcycle and helmet, a large steel tank, a ghost ship, and soccer and volleyballs. Out of the many beached vessels, a few have even been tracked back to their cities or owners!

The first Japanese debris to wash up on the Californian coast. Source

The first Japanese debris to wash up on the Californian coast. Source

One of two things happens with objects that are reported to local officials: they may be collected, packaged, and shipped to major project scientists or, items too large are photographed and organisms are scraped off, packaged, and shipped as preserved or dried material to major project scientists. In either case, analyses of organisms present is done.

Issues faced by JTMD researchers:

  • Belief that debris is radioactive (it is not)
  • Beach combers and cleaners throwing away objects before sampling can take place
  • Lack of specialized taxonomists
  • Separating Japanese from pelagic, beach, and west coast acquisitioned species
  • Inability to collect quantitative samples due to time constraints

Study of JTMD is done by picking and sorting. Each sample is rigorously searched and organisms are identified to the lowest possible taxonomic rank and put in their own separate, labeled vials. Annotations are made to account for relative abundance and when organisms contain tissue (i.e., barnacle shell vs. barnacle with body) or are reproductive (i.e., bryozoan embryos or amphipod with eggs). These vials will then be sent to taxonomic experts for identification to the species level. If enough specimens are present, those are vialed separately and sent in for genetic barcoding.

Current State of Knowledge

Today, only a portion of over 200 Japanese objects have been analyzed in depth, yet over 200 species have already been identified. Organisms as large as the pink acorn barnacle, Megabalanus rosa, to those as tiny as suctorians and foraminiferans are sorted out in each sample. We have seen the true Japanese versions of species like the bryozoan, Tricellaria inopinata, and the Asian shore crab, Hemigrapsus sanguineus, which have already invaded American coasts. We have seen fouled objects of varying materials and sizes that have appeared at very different times in very different locations with very different assemblages of species.

There are many uncertainties with JTMD: we don’t know how long the debris will continue to wash ashore from 5,000 miles away, what trajectory any object took, or which Japanese species will establish populations after being rafted in (Mytilus galloprovincialis, the Mediterranean mussel, which originated from Misawa 1, has already been found along Agate Beach, OR). One thing is certain though: a rafting study of this magnitude is unprecedented and we will take whatever information we can get.

I am honored to be a part of a project that is changing the state of knowledge about vectors of invasion, but every time I look through the scope I can’t help but feel sadness that this study is the result of such a devastating event.

Life truly is one big experiment.

Megan McCuller received a M.S. in Zoology from the University of New Hampshire in 2012 under her advisor, Dr. Larry Harris. Her research focused on the range expansion of a sea slug in response to climate change and availability of an invasive bryozoan as a food source. Megan currently works with Dr. Jim Carlton at Williams College-Mystic Seaport working on the JTMD project. In her spare time she studies the bryozoans of New England and has hobbies like XC skiing and crafting. Contact Megan at mccullermi@gmail.com or follow her on Twitter @mccullermi

Additional Resources

Time-lapse video of the removal of Misawa 3

Bryan, S.E., Cook, A.G., Evans, J.P., Hebden, K., Hurrey, L., Colls, P., Jell, J.S., Weatherley, D., Firn, J., 2012. Rapid, long-distance dispersal by pumice rafting. PLoS One. 7(7). e40583.

Calder, D.R., Choong, H.H.C., Carlton, J.T., Chapman, J.W., Miller, J.A., Geller, J.B. In press. Hydroids (Cnidaria: Hydrozoa) from Japanese tsunami marine debris washing ashore in the northwestern United States. Aquatic Invasions 9(4).

Thiel, M., Gutow, L. 2005. The ecology of rafting in the marine environment. II. The rafting organisms and community. Oceanography and Marine Biology: An Annual Review. 43. 279-418.

NOAA FAQs on JTMD and “Severe Marine Debris Event” Report (PDF)

Presentation: Japanese tsunami debris and invasive species: lessons being learned in Oregon and Applications for the Region