Pacific Coast Of Eastern Japan Research Articles

Characterization and spatiotemporal changes in the macrozoobenthic community structures at tidalflats along the Pacific coast of eastern Japan after the 2011 tsunamis using a large-scale survey data set

Characterization and spatiotemporal changes in the macrozoobenthic community structures at tidalflats along the Pacific coast of eastern Japan after the 2011 tsunamis using a large-scale survey data set

An Ecopath with Ecosim model for the Pacific coast of eastern Japan: Describing the marine environment and its fisheries prior to the Great East Japan earthquake

A mass balance model of the marine ecosystems is presented for the four prefectures of Japan prior to the Great East Japan earthquake. The Ecopath with Ecosim food web modelling approach and its Ecotracer routine were used to simulate the concentrations of 137Cs in the ocean and the biota in order to serve as baseline, , and to estimate the initial conditions for impact scenarios. Results of the Ecopath model were checked against pre-balance [PREBAL] diagnostics for integrity. 137Cs was shown to bioaccumulate with increases in trophic level, and has a tendency to biomagnify. Generally, for fish species, the dominant pathway of contaminant accumulation was through diet, whereas for invertebrates it was through respiration. Ecotracer was able to accurately model the expected concentrations in organisms that had existing concentration ratio data from field measurements, and also make predictions on biota lacking concentration data. In 2010, using national fishery landing statistics for the four prefectures and predicted whole body concentrations of 137Cs, it is estimated that the apparent direct and indirect human food supply of 137Cs from fisheries to the market was 46.1 MBq.

Abundance decline in the narrow‐ridged finless porpoise population off the Pacific coast of eastern Japan

AbstractThe narrow‐ridged finless porpoise Neophocaena asiaeorientalis is a small‐toothed whale with a coastal habitat and is sensitive to human activity. Aerial sighting surveys were conducted in 2012 to evaluate the abundance and distribution of the Sendai Bay‐Tokyo Bay population off the Pacific coast of eastern Japan. We flew along 35 east–west transects at intervals of 11.6 km over the study area between 34°57′ and 38°21’ N. In total, 25 groups were detected by two observers. The mean group size was 1.44 individuals. Porpoise abundance was estimated to be 1,491 individuals (coefficient of variation = 32.4%), which was lower than the abundance estimated in 2000 (z test, p < 0.05). A population decline trend during 2000–2012 was also detected using four available abundance estimates (Bootstrapping linear regression, p = 0.040). A possible cause of this decline was coastal habitat disturbance and deaths by tsunami waves caused by the 2011 Great East Japan Earthquake. Density was as low as 0.221 individuals/km2, which is among the lowest levels in Japanese waters. Furthermore, distributional gaps reconfirmed by the present study and past genetic studies show that the population should be divided into at least two populations: northern (“Sendai Bay‐Fukushima”) and southern. Density decline was detected in the northern population between 2000 and 2012. Unlike the earthquake, human activities may continue to affect the porpoises. Viability analyses of these small populations should be conducted in the future.

Radiostrontium monitoring of bivalves from the Pacific coast of eastern Japan.

In early April 2011, radiostrontium was accidentally released from the Fukushima Daiichi Nuclear Power Plant to the Pacific coast of eastern Japan. We developed a simple procedure to analyze radiostrontium levels in marine mussels (Septifer virgatus) and seawater using crown ether (Sr Resin; Eichrom). Then, we used our method to describe the spatial and temporal distribution of radiostrontium in mussels and seawater on the Pacific coast of eastern Japan from 2011 to 2013 and for 2015. Activity of (90)Sr in mussels and seawater decreased with distance from the Fukushima Daiichi Nuclear Power Plant and between 2011 and 2013 tended to be higher in areas south of the Fukushima Daiichi Nuclear Power Plant than to the north of it. Activity in mussels and seawater also tended to decrease from 2011 to 2013 and by 2015 had reached levels experienced prior to the Fukushima accident. Our results suggest that radiostrontium discharged from the Fukushima Daiichi Nuclear Power Plant was dispersed by coastal currents in a southerly direction along the Pacific coast of eastern Japan from 2011 to 2013, following which its activity decreased to background levels by 2015.

Genomic and metagenomic analysis of microbes in a soil environment affected by the 2011 Great East Japan Earthquake tsunami.

BackgroundThe Great East Japan Earthquake of 2011 triggered large tsunami waves, which flooded broad areas of land along the Pacific coast of eastern Japan and changed the soil environment drastically. However, the microbial characteristics of tsunami-affected soil at the genomic level remain largely unknown. In this study, we isolated microbes from a soil sample using general low-nutrient and seawater-based media to investigate microbial characteristics in tsunami-affected soil.ResultsAs expected, a greater proportion of strains isolated from the tsunami-affected soil than the unaffected soil grew in the seawater-based medium. Cultivable strains in both the general low-nutrient and seawater-based media were distributed in the genus Arthrobacter. Most importantly, whole-genome sequencing of four of the isolated Arthrobacter strains revealed independent losses of siderophore-synthesis genes from their genomes. Siderophores are low-molecular-weight, iron-chelating compounds that are secreted for iron uptake; thus, the loss of siderophore-synthesis genes indicates that these strains have adapted to environments with high-iron concentrations. Indeed, chemical analysis confirmed the investigated soil samples to be rich in iron, and culture experiments confirmed weak cultivability of some of these strains in iron-limited media. Furthermore, metagenomic analyses demonstrated over-representation of denitrification-related genes in the tsunami-affected soil sample, as well as the presence of pathogenic and marine-living genera and genes related to salt-tolerance.ConclusionsCollectively, the present results would provide an example of microbial characteristics of soil disturbed by the tsunami, which may give an insight into microbial adaptation to drastic environmental changes. Further analyses on microbial ecology after a tsunami are envisioned to develop a deeper understanding of the recovery processes of terrestrial microbial ecosystems.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2380-4) contains supplementary material, which is available to authorized users.

Status of 137Cs contamination in marine biota along the Pacific coast of eastern Japan derived from a dynamic biological model two years simulation following the Fukushima accident

Radiocesium (134Cs and 137Cs) released into the Fukushima coastal environment was transferred to marine biota inhabiting the Pacific Ocean coastal waters of eastern Japan. Though the levels in most of the edible marine species decreased overtime, radiocesium concentrations in some fishes were still remained higher than the Japanese regulatory limit for seafood products. In this study, a dynamic food chain transfer model was applied to reconstruct 137Cs levels in olive flounder by adopting the radiocesium concentrations in small demersal fish which constitute an important fraction of the diet of the olive flounder particularly inhabiting area near Fukushima. In addition, 137Cs levels in slime flounder were also simulated using reported radiocesium concentrations in some prey organisms. The simulated results from Onahama on the southern border of the Fukushima coastline, and at Choshi the southernmost point where the contaminated water mass was transported by the Oyashio current, were assessed in order to identify what can be explained from present information, and what remains to be clarified three years after the Fukushima Dai-ichi nuclear power plant (1FNPP) accident. As a result, the observed 137Cs concentrations in planktivorous fish and their predator fish could be explained by the theoretically-derived simulated levels. On the other hand, the slow 137Cs depuration in slime flounder can be attributed to uptake from unknown sources for which the uptake fluxes were of a similar magnitude as the excretion fluxes. Since the reported 137Cs concentrations in benthic invertebrates off Onahama were higher than the simulated values, radiocesium transfer from these benthic detritivorous invertebrates to slime flounder via ingestion was suggested as a cause for the observed slow depuration of 137Cs in demersal fish off southern Fukushima. Furthermore, the slower depuration in the demersal fish likely required an additional source of 137Cs, i.e. contaminated detritus or sediment which was entrained with the prey during the active sediment feeding of this fish species.

Detection of Fishing Grounds, Fishing Season, and Size Distribution of Stocked Barfin Flounder Verasper moseri in Southern Tohoku, the Pacific Coast of Eastern Japan

Detection of Fishing Grounds, Fishing Season, and Size Distribution of Stocked Barfin Flounder Verasper moseri in Southern Tohoku, the Pacific Coast of Eastern Japan

Collection Record and Feeding Habits of Larval Spotted Halibut and Stone Flounder in Coastal Shallow Waters off Fukushima, the Pacific Coast of Eastern Japan

Collection Record and Feeding Habits of Larval Spotted Halibut and Stone Flounder in Coastal Shallow Waters off Fukushima, the Pacific Coast of Eastern Japan

Evidence of viscoelastic deformation following the 2011 Tohoku‐Oki earthquake revealed from seafloor geodetic observation

AbstractThe GPS/acoustic seafloor positioning has detected significant postseismic movements after the 2011 Tohoku‐Oki earthquake (M9.0), just above the source region off the Pacific coast of eastern Japan. In contrast to the coastal Global Navigation Satellite Systems sites where trenchward‐upward movements were reported, the offshore sites above the main rupture zone in the northern part of the source region exhibit landward displacements of tens of centimeters with significant subsidence from almost 3 years of repeated observations. At the sites above around the edge of the main rupture zone, smaller amount of trench‐normal movements was found. Although the terrestrial movements were reasonably interpreted by afterslip beneath the coastal area, these offshore results are rather consistent with effects predicted from viscoelastic relaxation in the upper mantle, providing definitive evidence of its occurrence. On the other hand, the results in the southern part of the source region imply superposition of effects from viscoelastic relaxation and afterslip.

Ecological impacts of the 2011 Tohoku Earthquake Tsunami on aquatic animals in rice paddies

The 2011 Tohoku Earthquake Tsunami hit the Pacific coast of eastern Japan on March 11, 2011 and disturbed various ecosystems, including rice paddies along the coast. In Miyagi Prefecture, located in the Tohoku Region, a total of 12685 ha, or about 11.5 % of the rice paddies, were inundated and damaged by the tsunami. Although rice paddies are artificially constructed, they have long been used by many kinds of aquatic animals as habitats. To assess impacts of the 2011 Tohoku Earthquake Tsunami on aquatic animals inhabiting the rice paddies, census surveys were conducted at inundated and non-inundated rice paddies at six sites along the coast of Miyagi Prefecture from June to July 2012. This was 30–60 days after the first transplanting of rice seedling in inundated rice paddies following the tsunami. In the surveys a total of 100 aquatic animal taxa, 72 from inundated and 86 from non-inundated rice paddies, were found. Although the taxonomic richness and composition differed among the sites, the total number of observations of walk dispersers and obligatory aquatic animals without resting stages were significantly lower in inundated than in non-inundated rice paddies. However, no notable difference was detected in taxonomic richness and the total number of observations of flight dispersers and obligatory aquatic animals with resting stages between inundated and non-inundated rice paddies. The results showed that the tsunami had a substantial impact on freshwater animals but that restoration of the paddies for rice cultivation enhanced rapid recolonization by aquatic animals with high dispersal abilities and resting stages.

史料に記録された中世における東日本太平洋沿岸の津波

To find tsunamis that affected the Pacific coast of eastern Japan during period between A.D. 869 and the 1600s, we searched a historical earthquake and tsunami database for tsunami descriptions. We examined reliability of the descriptions considering the written dates and independence of documents. As a result, at least two events were found. One is the Oei tsunami which occurred on September 1st, 1420 on the Julian calendar (the 7th month 23rd day, 27th year of Oei era on the Japanese calendar). The tsunami affected Kawarago and Aiga villages in Hitachi city, Ibaraki prefecture. Sea receded 9 times during 4 hours, exposing the coastal seafloor, and many fish were carried to the land. No description of earthquake ground shaking was found. The other is the Kyotoku earthquake tsunami which occurred on December 12th, 1454 (11th month 23rd day, 3rd year of Kyotoku era). An earthquake occurred in night and the tsunami widely inundated the coastal area of “Oshu” (the old name of province from Aomori to Fukushima prefectures). Many people were killed in the tsunami. Another entry in the database on December 31st, 1455 (11th month 23rd day, first year of Kosho era) is likely to be a fake event.

Immediate Ecological Impacts of the 2011 Tohoku Earthquake Tsunami on Intertidal Flat Communities

Following the Great East Japan Earthquake in 2011, a large tsunami developed and struck the Pacific coast of eastern Japan. To assess the immediate impacts of the tsunami on coastal communities, changes in taxon composition and richness of macrobenthic animals before and after the tsunami were examined at nine intertidal flats in Sendai Bay and the Sanriku Ria coast. The results showed that 30–80% of taxa indigenously inhabiting intertidal flats disappeared after the tsunami. Among animal types, endobenthic and sessile epibenthic animals were more vulnerable to the tsunami than mobile epibenthic animals like shore crabs and snails. For all the intertidal flats examined, animals that were originally dwellers in lower tidal zones and not recorded before the tsunami were also found right after the tsunami, indicating that the tsunami not only took away many benthic taxa from the intertidal flats but also brought in some taxa from elsewhere. However, overall changes in taxon community composition were greater for intertidal flats that experienced larger inundation heights. These results showed that the ecological impacts of the tsunami were proportional to the physical impacts as gauged by wave height and that mobile epibenthic animals were less vulnerable to the tsunami.

The Mega-Tsunami along the Pacific Coast of Eastern Japan in March, 2011 and the Shrine

The Mega-Tsunami along the Pacific Coast of Eastern Japan in March, 2011 and the Shrine

The reconstruction of transportation and environmental infrastructure in rural areas

On March 11, 2011 a massive, magnitude 9.0 earthquake destroyed most of the rural areas along the Pacific Coast of eastern Japan, an area that had been facing issues of depopulation and aging even before the earthquake. In this paper I discuss reconstruction plans for depopulated rural areas from the perspectives of transportation infrastructure, residential areas, agriculture, forestry, fisheries, consensus building, and nature restoration. We must take a “backcasting” approach to sustainable development, one in which planning strategies lead to successful outcomes. An organizational and planning support platform is needed to build a consensus within an area.

Lateral variation of the cutoff depth of shallow earthquakes beneath the Japan Islands and its implications for seismogenesis

We estimated the spatial distribution of the cut-off depth of shallow seismicity beneath the Japan Islands based on data from a recently constructed nationwide dense seismic network. In order to avoid the effect of heterogeneous seismic velocity structure, we determined the 3D seismic velocity structure for the whole of Japan, which was then used to relocate the hypocenters. The cut-off depth was determined by calculating D90, the depth above which 90% of the earthquakes occur. A spatial distribution of estimated D90 values shows a considerable lateral variation, ranging from about 5km to about 40km. The D90's are deep along the Pacific coast of eastern Japan. Locally shallow D90's extend along belt-like stretches of volcanic areas. Heat flow is low along the Pacific coast in eastern Japan and high in the volcanic areas. This indicates that the lateral variation of D90's is formed mainly by lateral geotherm variation. Cooling by the subducting old, very cold Pacific plate may cause the deep D90's along the Pacific coast in eastern Japan. Heating by magma supplied from the mantle wedge below is considered to be the main cause of the shallow D90's in the volcanic areas. Magma and/or aqueous fluids derived from solidified magma contribute not only to locally shallow D90's but also to the weakening of ambient rocks in the lower crust, resulting in stress concentrations in the upper crust just above them. Large shallow inland earthquakes tend to occur in such areas, suggesting that a model of shallow earthquake generation applied to Tohoku can be used in other areas in Japan as well.

Effect of Simultaneous Consideration for Seismically Induced Events on Core Damage Frequency

The purpose of this study is to investigate the effects of the consideration of simultaneous occurrence of seismically induced events in Nuclear Power Plants (NPPs) such as failures of components due to seismic stress, seismically induced fire, and seismically induced internal flooding in seismic probabilistic safety assessment(PSA). The seismic risk is estimated in terms of the Core Damage Frequency (CDF) and the CDF is comprised of occurrence frequencies of accident sequences. In this study, two analytical methods, upper bound approximation (UBA) using minimal cut sets (MCSs) and direct quantification of fault tree using Monte Carlo simulation (DQFM) are selected for comparison. The results showed that the simultaneous occurrence of seismically induced events should be reasonably considered to assess the intersection and the union of these events. In addition, the Great Eastern Japan Earthquake and the Tsunami damaged NPPs on the Pacific Coast of Eastern Japan on March 11, 2011 will be examined in this study.

Phylogenetic relationship of two Mola sunfishes (Tetraodontiformes: Molidae) occurring around the coast of Japan, with notes on their geographical distribution and morphological characteristics

Phylogenetic analyses were conducted using complete nucleotide sequences of the D-loop in the mitochondrial genome of Mola specimens, collected mainly in Japanese waters, to clarify the genetic features and distribution patterns of Mola sunfishes. Two significantly distinct groups (designated A and B) were present in the genus, with a considerable net nucleotide sequence divergence between the two (8.4%). The two groups occurred sympatrically around the Japanese coast, as previously suggested by Sagara et al. (2005). Group A occurred mostly on the Pacific coast of eastern Japan, while group B was widely distributed along the Kuroshio Current, strongly suggesting different migration routes for each group. The morphological characteristics of the two group specimens were differentiated via the head bump, body proportions and shape of the clavus. Through the addition of Mola sequence data taken from outside Japan to our phylogenetic analyses, three independent groups, including groups A and B, were found, each with a wide geographical distribution, which suggests the presence of at least three independent species within the genus Mola.

船舶調査から推定した日本周辺におけるアホウドリの海上生息域

The pelagic distribution of the Short-tailed Albatross Phoebastria albatrus in the western North Pacific o# the Nansei Islands to eastern Japan was examined from data collected by research vessels from 1999 to 2004. Fifteen groups and 325 individuals of Short-tailed Albatrosses were recorded during line-transect sighting surveys, and 25 groups and 45 individuals were recorded in opportunistic observations during cruising, drifting and experimental fishing. Results of the sighting survey revealed that Short-tailed Albatrosses appeared in three areas o# Japan from the fourth quarter to the next second quarter: 1) o# the Pacific coast of eastern Japan, 2) near Torishima of the Izu Islands, and 3) near Minamikojima of the Senkaku Islands. Geographical analysis of the occurrence points showed that large numbers of Short-tailed Albatrosses aggregated in the near-shore waters within 30 km of the breeding islands, and that they also utilized the Kuroshio Oyashio mixture zone above the continental shelf edge and slope 2001400 m in depth and 2070 km o#shore of the Pacific coast of eastern Japan. Results of this study suggest that ar esting area near the breeding islands and a foraging area above the continental slope o# eastern Japan are important marine habitats for the Short-tailed Albatross during the breeding period.

Ground-penetrating radar profiles of Holocene raised-beach deposits in the Kujukuri strand plain, Pacific coast of eastern Japan

Ground-penetrating radar (GPR) profiles of Holocene beach deposits were documented from the Kujukuri strand plain, Pacific coast of Japan, to examine a marker of past sea level recognized in these profiles. The Kujukuri strand plain has been uplifted over the last 6000 years, with a total relative sea-level fall of about 5 m suggested by seaward lowering of the lithologic boundary between the foreshore and upper shoreface facies. A GPR survey was performed on a modern aeolian dune and beach ridges of the strand plain using a PulseEkko100 system with 100-MHz antennae. The profiles obtained contain five vertically stacked radar units (R1–R5) with characteristic reflections. Ground truthing using sediment cores and the morphology of the modern beach suggest that these radar units correspond to aeolian dune (R1), small-scale swale (R2), backshore and foreshore (R3), upper shoreface (R4), and lower shoreface (R5) deposits, in descending order. The backshore and foreshore radar unit shows a sequence of continuous reflections dipping seaward at an angle consistent with the modern beach, whereas the underlying upper shoreface radar unit represents complicated and less-continuous reflections. The boundary between these two units is a downlap surface of the foreshore reflections, and is thought to have formed at about 1 m below the mean sea level at the time of deposition. The lateral tracing of the boundary in radar profiles across the strand plain indicates a total fall in relative sea level of 5 m, which is consistent with the drill core results. Radar profiles of the foreshore and upper shoreface deposits in the Kujukuri strand plain thus provide a past sea-level indicator that is available without drilling sediment cores.

Intra‐shoreface erosion in response to rapid sea‐level fall: depositional record of a tectonically uplifted strand plain, Pacific coast of Japan

AbstractThis study documents lowering of the surf zone (i.e. the upper shoreface) leading to intra‐shoreface erosion, following two rapid relative sea‐level falls along a tectonically uplifted coast during the Holocene, and the characteristics of the resultant prograding shoreface deposits. These findings are based on high‐resolution analysis and radiocarbon dating of three new drill cores obtained from the Kujukuri strand plain, Pacific coast of eastern Japan, combined with previously published borehole data and information on modern shoreline profile adjustments. A shallowing‐upward sandy succession composed of lower and upper shoreface facies, foreshore and backshore facies was recognized in the drill cores. Two rapid falls in relative sea‐level at 2·3 to 2·6 and 1·8 to 2·0 ka are recorded by downstepping of the base of the foreshore facies, and farther seawards by the lowering of an erosional boundary between the upper and lower shoreface facies. Superimposed bed profiles of an adjacent modern beach define an envelope, the base of which reflects shore‐normal migration of longshore bars and troughs. The base of the envelope represents an erosional surface that divides the surface mobile layer above from preserved deposits beneath. The surface is concave upwards and steeper than the mean beach profile, and exhibits a flat platform approximately at the lower limit of the upper shoreface equating to the storm surf zone. The seaward transition of this surface, rather than the mean equilibrium profile, controls the metre‐scale to decimetre‐scale internal structure of the Kujukuri shoreface deposits. Depositional models for sea‐level fall based on an exponential equilibrium profile do not adequately account for the presence and migration of longshore bars and troughs.