THE FATE OF THE TOHOKU TSUNAMI DEBRIS FIELD

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region (Bertero, 2011;Lekkas et al., 2011).e ensuing tsunami inundated an area of about 561 km 2 (Geospatial Information Authority, 2011), washing away an estimated 24.9 million tonnes of debris, including wood, sediments, plastics, industrial chemicals, and structural components (Oh, 2011).Two weeks following the tsunami, the meltdown of the Fukushima Daiichi nuclear reactors released radioactive elements into the atmosphere and coastal waters.
Atmospheric deposition was found to be an important source of radioactivity in surface waters and may have contaminated the debris eld, although the extent of this contamination remains unknown (Buesseler et al., 2012;Honda et al., 2012).
Here, we follow the debris eld along its predicted path from its source exchange (Buesseler et al., 2012).Some of the radioactive elements were also released into the atmosphere, where they could have travelled signi cant distances before deposition (Honda et al., 2012).
Elevated levels of radiation found in sh samples led the Japanese govern-  (Gadd, 1999;Heldal et al., 2001;Burger et al., 2006;Kaeriyama et al., 2008;Morita et al., 2010;Hong et al., 2011).e radioactive signature of the Fukushima Daiichi disaster could persist locally for the life of the isotopes, as contaminated sediments are remobilized through physical processes, chemical changes, and biological activity (Fisher et al., 1991;Vives i Batlle, 2011).

KUROSHIOOYASHIO E XTENSION
Within a month, the debris eld entered  into these waters by atmospheric transport and subsequent deposition. is process could explain the high levels of cesium-137 in samples gathered several hundred kilometers o shore of Japan (Buesseler et al., 2012).Radionuclides in suspended solids and zooplankton were up to two orders of magnitude higher than background levels, demonstrating that bioaccumulation is already occurring (Honda et al., 2012).
FAD-based shing using purse seines catches younger individuals, in contrast to longline sets that primarily catch adults (Fonteneau et al., 2000).Because the debris eld e ectively increases the number of FADs, focused shery e ort on them may result in over shing of juveniles, which may reduce the breeding stock.
As timber from ~ 400,000 destroyed buildings transits the Paci c Ocean, it will become water-logged and sink at varying rates, some landing on the seaoor within the NPC and some reaching the California Current (National Police

Agency of Japan Emergency Disaster
Countermeasures Headquarters, 2012).
As wood sinks, the potential habitat of wood-fall and opportunistic species may increase dramatically (Gooday, 2002).Some bivalves, crustaceans, and polychaetes may bene t from the increased abundance of wood falls (Kiel and Goedert, 2006;Bernardino et al., 2010).
ough certain early colonizing bivalves recruit poorly on the copper-treated lumber typical of Japanese construction (Japan Wood Preserving Association, 2012), wood-boring crustaceans may be uninhibited by the preservatives (Distel, 2003).e abundance and composition of the sunken debris could cause atypical successions and community compositions that may last a decade or more.Showstack, 2011).In addition to being a productive region characterized by seasonal upwelling, the CCS is a common ground for many pelagic predators, and many trans-Paci c migratory pathways converge within its waters (Block et al., 2011).Already, within one year of the tsunami, shing oats, nets, and plastics identi able as coming from Japan have washed ashore in Alaska, British

CALIFORNIA CURRENT SYSTEM
Columbia, and Washington-much earlier than simulation models predicted (International Paci c Research Center, 2011b; Maximenko and Hafner, 2012).
e probability of successful invasion along the CCS by a ra ing species depends upon the life history of the organisms, the duration and path of transport, and the resilience of the Figure 3. Satellite tracks of migratory tunas (yellow), sea turtles (orange), and seabirds (purple) superimposed upon the projected coverage of the debris field (red).Regions of overlap are crosshatched.Adapted from Block et al. (2011) invaded ecosystem ( iel and Gutow, 2005).e west coast of North America is recognized as the most invaded region on the continent, primarily in high-tra c ports such as San Francisco (Ruiz et al., 2000), with the most invasive species previously originating from Indonesia (Ruiz et al., 2000;Williams and Smith, 2007).e tsunami debris eld may be an unprecedented source of potentially invasive species to the CCS ecosystem, its $500 million shing industry (National Marine Fisheries Service, 2010), and its associated coastal and benthic habitats.
On the west coast of North America, large woody debris expelled from rivers has been the source of habitat for deepsea communities (Kiel and Goedert, 2006).In the last century, however, this supply was greatly reduced by human enterprise, especially river damming, deforestation, and the harvest of oating timber (Dolo , 1993;Moulin and Piegay, 2004). is ongoing "deep-sea deforestation" may be temporarily o set by the in ux of new-albeit chemically treated-woody habitat from the debris eld, thus increasing the biomass of some wood-fall associated species.

HAWAIIAN ISL ANDS
e increasingly fragmented debris is predicted to reach the shores of the Hawaiian archipelago four years a er the tsunami.Many migratory, endangered, and endemic species rely upon this island chain and will probably be threatened by the in ux of debris (Polovina et al., 2001(Polovina et al., , 2008)).e oating wreckage may still contain nonbiodegradable shing gear from Tohoku that could entangle, injure, and kill large numbers of marine mammals, seabirds, and coral reef communities (Donohue et al., 2001;Chiappone et al., 2005;Brown and Macfadyen, 2007).
e debris may prove to be disastrous for the endangered Hawaiian monk seal (Monachus schauinslandi), whose population is already decreasing by 4% annually (Baker et al., 2011;Lowry et al., 2011).With the highest annual entanglement rate among all pinnipeds (Henderson, 2001), this population will likely experience increased mortality caused by the lost shing gear.
Entanglement deaths of the endangered hawksbill turtle (Eretmochelys imbricata) of the Northwest Hawaiian Islands have decreased from 20 to one or two annually due to bycatch mitigation (Donohue et al., 2001;Finkbeiner et al., 2011); sadly, the debris may reverse this trend.
Plastics in the debris eld may be ingested by a variety of marine mammals and seabirds (Derraik, 2002).Sea turtles (Carr, 1987) and Hawaiian albatrosses (Young et al., 2009) are especially prone to consuming degraded plastic debris that is mistaken for, or aggregated around, their natural prey.Albatross chicks fed plastic parts by their parents can die before ever going to sea; plastics can cause physical trauma and blockages in the digestive tract or reduce the urge to feed, leading to starvation (Young et al., 2009).where plastics and other oating debris accumulate and persist for decades (Venrick et al., 1973;Rios et al., 2010).

NORTH PACIFIC GYRE
It is hypothesized that such material will eventually degrade and lose buoyancy due to biofouling by organisms and sediment (Barnes et al., 2009).However, the time frame of suspension in the water column remains unknown (Ye and Andrady, 1991).
Plastics in the NPG a ect shes, seabirds, turtles, and marine mammals, as well as commercially important sheries.
In addition to the previously mentioned  and also adsorb organic contaminants already present in seawater (Artham and Doble, 2009;Rios et al., 2010).
Organisms that ingest plastics, or are associated with contaminated water, may be at risk from the deleterious e ects of these chemicals, causing, for example, disruption of endocrine, reproductive, and immune systems, and, potentially, neurobehavioral disorders and cancer (Jones and de Voogt, 1999).While it is too soon to speculate on the impact of these contaminant pathways, these chemicals may persist in the marine environment and, under certain conditions, be transferred to marine organisms (Teuten et al., 2009).

CONCLUSIONS
Here, we have presented a Lagrangian M A L B A G U L AYA N , J I N A E N .B A R T L E T T R O A , A M A N D A L .C A R T E R , B R Y C E G .I N M A N , E R I C M .K E E N , E R I C C .O R E N S T E I N ,N A S TA S S I A V. PAT I N , K I R K N .S .S AT O , E L I Z A B E T H C .S I B E R T, A N N E E .S I M O N I S , A M Y M .VA N C I S E , A N D P E T E R J .S .F R A N K S R E G U L A R I S S U E F E AT U R E INTRODUC TION e 9.0 magnitude Tohoku earthquake that struck o the coast of Japan on March 11, 2011, was the fourth largest earthquake in recorded history and the largest ever to hit a densely populated

in
Japanese coastal waters through the Kuroshio-Oyashio Extension, the North Paci c Current, and the California Current.From there, it will loop back toward the Hawaiian Islands, ultimately accumulating in the North Paci c Gyre (International Paci c Research Center, 2011b; Figure 1).Relying on precedents from previous natural disasters and ongoing observations, we attempt to predict the impact of this debris eld on marine and coastal ecosystems in each of these regions.We predict that the Tohoku debris eld will create a rare perturbation for ecosystems interconnected across the North Paci c, exacerbating the accumulating human impacts on the world ocean.COASTAL JAPANESE WATERS Chemical contaminants and debris were carried over Japan's narrow eastern continental shelf, home to a multibilliondollar shing industry (Johnson, 2011), passing through habitats for plankton, benthic invertebrates, sh larvae, and many transitory pelagic sh.Sea oor observations by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) suggested that receding waves kept nearshore bays, coves, and o shore trenches relatively clear of debris (K.Fujikura and H. Kitazato,JAMSTEC, pers.comm., Nov. 23, 2011).Larger objects may have scoured swaths of the continental shelf as they were carried o shore.e nuclear ssion reactor meltdowns at Fukushima Daiichi released radioactive isotopes with ecologically relevant half-lives, such as cesium-134 (2 yr), cesium-137 (30 yr), and strontium-90 (29 yr)(Kaeriyama et al., 2008;Hong et al., 2011).A large amount of iodine-131, known to cause thyroid cancer in humans(Morita et al., 2010), was also introduced.Due to iodine's short half-life (8 d), its ecological impact is presumed to be minimal and geographically restricted.Strong nearshore currents advected radioactively contaminated water northeastward into the open Paci c, but the Kuroshio Current acted as a boundary to more southerly THE FATE OF THE TOHOKU TSUNAMI DEBRIS FIELD ment to institute a local moratorium on shing that was still in place as of May 2012 (Institute of Electrical and Electronics Engineers, 2012).Although this moratorium addressed short-term contamination, long-lived radioactive isotopes could be incorporated into sediment, phytoplankton, and brown algae, eventually bioaccumulating in higher trophic levels such as copepods, molluscs, polychaetes, and shes, all of which are directly or indirectly consumed by humans harvesting from coastal waters the productive waters of the Kuroshio-Oyashio Extension (KOE) region, a major con uence of Paci c western boundary currents.is timing corresponded with the annual spring phytoplankton bloom that governs ecosystem dynamics across the North Paci c (Figure 2; Saito et al., 2002; Liu et al., 2004).Following a tsunami, primary productivity may increase in response to nutrient loading.For example, immediately following the 2004 Indian Ocean tsunami, nutrients and phytoplankton increased near the earthquake's epicenter (Murty et al., 2007; Satheesh and Wesley, 2009; Yan and Tang, 2009).Our analyses of MODIS satellite data from the KOE between 2003 and 2011 (http:// oceancolor.gsfc.nasa.gov/cgi/l3)suggest that the 2011 spring phytoplankton bloom initiated earlier in the year (March, rather than early April), and was signi cantly higher (t-test, 2460 df, p << .001)for that month than in any other year since 2003 (Figure 2). is circumstance may have been a consequence of increased nutrient input from the tsunami, due either to deep mixing or terrestrial runo .ough the KOE extends far o shore, radioactive elements can be introduced Amal Bagulayan, Jinae N. Bartlett-Roa, Amanda L. Carter, Bryce G. Inman, Eric M. Keen, Eric C. Orenstein, Nastassia V. Patin, Kirk N.S.Sato, Elizabeth C. Sibert, Anne E. Simonis, and Amy M. Van Cise are students in the biological oceanography class SIO280, and Peter J.S. Franks (pfranks@ucsd.edu) is Professor, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.

Figure 1 .
Figure 1. e projected path of the Tohoku tsunami debris field showing the expected arrival time of debris at each major geographic area covered in this review.Darker shades represent increasing probability of debris occurrence.Debris path adapted from IPRC (2011b).Bathymetry modified from an image by Hiroyasu Hasumi, University of Tokyo.

Figure 2 .
Figure 2. Satellite remotely sensed chlorophyll 2003-2011.Upper panels: Marchaveraged MODIS satellite surface chlorophyll data from near Japan.Black areas are either land or cloud-covered.Lower panel: Mean, mean + standard deviation, and maximum chlorophyll a value from the boxed region in each satellite image.

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convergence zone of the North Paci c Gyre (NPG) is the predicted nal resting place for much of the Japanese tsunami debris eld, particularly oating plastics.e gyre's center is home to the North Paci c Garbage Patch, a region physical e ects of intestinal blockage, entanglement, and su ocation that lead to mortality, many chemical e ects can be associated with the breakdown of plastic debris.Degrading plastics leach a broad spectrum of chemical additives " HERE, WE HAVE PRESENTED A LAGRANGIAN VIEW OF THE TOHOKU DEBRIS FIELD, FROM COASTAL SOURCE TO ABYSSAL SINK, AS IT DRIFTS THROUGH THE ECOSYSTEMS, TROPHIC WEBS, AND WATER COLUMN OF THE NORTH PACIFIC.

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view of the Tohoku debris eld, from coastal source to abyssal sink, as it dri s through the ecosystems, trophic webs, and water column of the North Paci c. e international community needs to come together to develop a plan to mitigate the e ects of the Tohoku tsunami debris eld.Although our predictions are necessarily speculative, some e ects are easier than others to identify.For example, while the chemical e ects of bioaccumulation are di cult to predict, entanglement from debris may have a negative impact on commercially important and endangered species.Consequently, directed e orts to remove debris around a ected islands or coastlines will likely be a worthwhile investment.Additionally, to avoid over shing of juvenile tunas and other shes associated with FADs, it is advisable to manage shing e ort in debris-a ected areas.Although its journey makes for a memorable story, within decades, the debris will assimilate into the countless tons of garbage already accumulating in the central North Paci c.While this is an unprecedented in ux of debris, the widespread short-term e ects will only be a pulse in the rising levels of anthropogenic impacts to the ocean.ACKNOWLEDGEMENTS e topic of this paper was assigned as a term project to SIO280, the graduatelevel introductory biological oceanography course at Scripps Institution of Oceanography taught by Peter Franks.e 35 students, representing all the disciplines at Scripps, submitted nine group papers that were subsequently synthesized into this paper by the named authors.e remaining