Japanese Coast Research Articles

Projection of Shoreline Retreat due to Sea Level Rise along Japanese Coasts

Sea level rise due to climate change is expected to increase coastal erosion and thus result in serious coastal disasters. Along the Japanese coasts, existing projections of the sea level rise show 9-27 cm rise at the end of 21st century; however, there is few study on its effect on the Japanese coastal erosion after Mimura et al. (1994). In this study, observed wave and tidal data were analyzed to investigate characteristics of their long-term trends and then future beach erosion along the Japanese coasts was projected using the Bruun rule for SRES A1B scenario. The observed data analyses demonstrate that the annual average and maximum tide levels and the annual maximum wave height tended to increase at rates of 0.4, 0.4 and 3.9 cm/yr, respectively, in recent decades. Due to these factors, beach erosion was projected to be 10-50 m.

Evaluation of Storm Surge Risk Directly Based on Climate Change Projection

Future storm surge risk due to the tropical cyclones (TC) in East Asia is evaluated where the climate change projection by the state-of-the-art atmospheric GCM is employed as driving forces for storm surge simulations. The reproducibility or validity of TC characteristics by the GCM in the northwest Pacific is confirmed comparing with the observed best track data, and future TC change is presented. Storm surge simulations are carried out in the East Asia with the finest nested domain on Japanese coast. Probability of maximum storm surge heights with several return periods are analyzed by extreme statistics. It was found that there are strong regional dependencies on the change of magnitudes of severe storm surge anomalies in the future climate.

津波警報発令時における湾内の船舶の避航・避泊行動に関する調査研究

External forces of marine weather, such as waves, currents and wind flows, affect the course and speed of a ship under way. As a result, marine accidents, such as collisions or grounding, may occur, particularly in inshore areas. On coasts where earthquakes and tsunamis occur frequently, such as the Japanese coast, a tsunami that advances into a bay from the open sea is influenced by the submarine topography. It grows into a huge wave that could cause tremendous damage to ships under way and at anchorage. A massive earthquake occurred in the Tohoku and Kanto regions of Japan on 11 March 2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behaviour of ships by AIS data in Tokyo bay and Osaka bay after the tsunami warning was issued. The unusual behaviour observed was attributed to the emergency evacuation of ships. In addition, the propagation direction of the tsunami was clarified by analysing the drift situation of each ship.

Contamination status and spatial distribution of organochlorine compounds in fishes from Nansei Islands, Japan

Two species of fishes (n=52; tilapia and mullet) from industrialized and urbanized areas of Okinawa Island (Manko-Noha river, Hija river and Shikaza river) and from a remote area of Ishigaki Island (Anparu mudflat), Japan were collected between August 2005 and July 2006, and analyzed for five organochlorine compounds (OCs), viz., DDTs, PCBs, CHLs, HCHs and HCB. Concentrations and the contamination patterns of OCs in fishes varied between locations. Considerable residue levels of OCs, especially CHLs and DDTs were found in both fishes from the main Okinawa Island. These levels were relatively higher than the reported values for seafood from Japanese coasts, indicating that even now pollution sources of these contaminants still exist in this region. On the other hand, lower concentrations of OCs were detected in fishes from Ishigaki Island waters than those of other Japanese coastal waters, suggesting that this region is less contaminated by OC contaminants.

2）原発事故が地域にもたらしたもの〜福島の大震災の特異性〜

After the catastrophic 2011 Tohoku earthquake and tsunami which struck cities and towns on the Japanese Pacific coast, Fukushima has been the focus of special and serious disaster relief procedures modification regarding nuclear power plant accidents. To date, the Japanese government has repeatedly issued evacuation orders to more than 100,000 residents. Huge numbers of refugees are still uncertain if they can return home and re-cultivate their farm land. Ambiguous public announcements concerning the radiation risks seem to have aggravated feelings of insecurity, fear and the desire to escape, both at home and abroad. This disaster has seriously undermined trust internationally and locally in Fukushima. Harmful rumors added further difficulties. In response to this disaster, local government, medical institutions, care facilities, police, emergency services and the self-defense forces continue to put their utmost effort into reconstruction. This seismic disaster has reminded us that supplies of water, electricity, gas, gasoline and telephone/communication facilities are essential prerequisites for reconstruction and daily life. Disaster and radiation medical association teams actively participated in the rescue efforts, and a number of organized medical teams cared for about 15,000 refugees in 100 shelters. We also visited home-bound patients, who were unable to evacuate from the 20-30 km inner evacuation area. In this relief role, we need to consider the following; (1) professionals, both healthcare and nuclear engineers, must always be prepared for unexpected circumstances, (2) the daily organic cooperation of individuals and units is closely linked to readiness against sudden risks, and (3) appropriate accountability is essential to assuage the fears of residents and refugees. A sincere learning process may benefit those innocent refugees who may be forced to abandon their homes permanently.

Water Column Profiles of Dissolved Inorganic Radiocarbon for the Kuroshio Region, Offshore of the Southern Japanese Coast

We present the water column profiles (surface to 2000 m depth) for dissolved inorganic radiocarbon (14CDIC) from 2 stations in the Kuroshio region including the Kuroshio large meander (LM) of 2004–2005. Surprisingly, the Δ14CDIC value varied up to 125‰ in the intermediate layer, especially near 600 m depth. In addition, the Δ14CDIC value was approximately − 150‰ at 200 m depth at the northern station of Kuroshio in August 2005. This value is ∼100‰ less than other Δ14CDIC values for the same depth. In comparison, the Δ14CDIC water column profiles for the southern station of Kuroshio and GEOSECS station 224 decrease down to 600 m depth and were similar below 600 m depth. Our results suggest that strong upwelling associated with the Kuroshio LM has a powerful influence on the Δ14CDIC water column profiles in the study region.

Sea-ice extent variation along the coast of Hokkaido, Japan: Earth’s lowest-latitude occurrence of sea ice and its relation to changing climate

AbstarctThe seasonal duration of sea-ice cover in the region immediately north of Hokkaido in the Sea of Okhotsk was estimated from daily sea-ice concentration maps (1995–2009) produced by the Japanese Coast Guard. The results show that this period is generally well represented by the proxy record of sea-ice duration in the region of Utoro in the Shiretoko peninsula. Comparison of the duration of seasonal sea-ice cover along the coast of Hokkaido with meteorological conditions over the period of sea-ice mapping by the Japanese Coast Guard indicates that all sea ice will disappear from the coast of Hokkaido once air temperature is increased by 2–4˚C over present values by the effects of climate change.

Species-specific detection and quantification of common barnacle larvae from the Japanese coast using quantitative real-time PCR

Species-specific detection and quantification methods for barnacle larvae using quantitative real-time polymerase chain reaction (qPCR) were developed. Species-specific primers for qPCR were designed for 13 barnacle species in the mitochondrial 12S ribosomal RNA gene region. Primer specificity was examined by PCR using template DNA extracted from each of the 13 barnacle species, other unidentified barnacle species, and field collected zooplankton samples. The resulting PCR products comprised single bands following agarose gel electrophoresis when the templates corresponded to primers. The amplifications were highly species-specific even for the field plankton samples. The field plankton samples were subjected to qPCR assay. The calculated DNA contents for each barnacle species were closely correlated with the number of larvae measured by microscopic examination. The method could be applied to quantify barnacle larvae in natural plankton samples.

Spatial variation in otolith elemental composition of the Pacific herring Clupea pallasii in northern Japan

In order to examine whether otolith elemental composition of Pacific herring Clupea pallasii reflected spatially specific differences in capture location, we analyzed the elemental compo- sitions in the edge portion of each otolith, which corresponded to the period immediately prior to the capture, as an indicator of the geographic areas in which the outer otolith was deposited. We col- lected 7 fish groups from 5 coastal sites: Tomamae offshore, Ishikari Bay, Akkeshi Bay, Lake Furen and Miyako Bay along the Japanese coast. Six elemental ratios, Na/Ca, Mg/Ca, K/Ca, Cu/Ca, Sr/Ca and Ba/Ca, were measured in the edge areas of each otolith by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Significant differences were shown in all mean elemental ratios of otoliths among 4 sampling groups in the 2005 year class and among 3 sampling groups in the 2006 year class. The classification accuracy with the jackknife cross-validation using quadratic dis- criminant function analysis ranged from 80 to 98% and 78 to 100% in the 2005 and 2006 year classes, respectively. Our findings are comparable to those in previous studies and are further evidence that otolith chemistry is a potential tool for identifying the Pacific herring groups with different habitat- use histories and migration patterns.

A Chill in China-Japan Academic Relations

A diplomatic tiff stemming from a collision last month between a Chinese trawler and two Japanese coast guard vessels has chilled academic exchange between the two countries.

Genetic structure in species with shallow evolutionary lineages: a case study of the rare flatfish Verasper variegatus

We examined the genetic population divergence of the spotted halibut Verasper variegatus. A previous report suggested two conservation units for this species along the Japanese Pacific coast. Extending the coverage of the genomes (29 microsatellites and three mitochondrial DNA segments) revealed hitherto-undetected genetic population boundaries. We screened population samples from the major habitats along the Japanese coast and the Yellow Sea coast (East Asian Continent). Significant genetic differentiation was found in every comparison between the habitats. In most cases, the nuclear and mitochondrial population divergences were incongruent, most likely caused by differences between the two genomes in the effects of genetic drift after recent population isolation and bottleneck events. We discuss the ecological and evolutionary mechanisms of the genetic structure as well as the units of conservation. The present study illustrates the merits of wider coverage of genomes in genetic population analysis especially for species with a shallow population history.

Atmospheric Effects of the Kuroshio Large Meander during 2004–05*

Abstract In the summer of 2004, the Kuroshio took a large meander path south of Japan for the first time since 1991, and this large meander event persisted until the next summer. Satellite observations and numerical model simulations are used to study the effect of this large meander event on the atmosphere. The large meander leaves a cool water pool between the Kuroshio and Japanese coast. Sea surface temperature (SST) in the cool water pool is about 2°–3°C colder than the surroundings during winter and spring, whereas the SST signature substantially weakens in summer. A local reduction of wind speed is found over the cool water pool, and the positive SST–wind speed correlation is indicative of ocean forcing of the atmosphere. Cloud liquid water (CLW) content and precipitation also decrease over the cool SST pool. A regional atmospheric model successfully simulates atmospheric response to the Kuroshio large meander. The model experiments suggest that the reduced surface wind speed and precipitation are due to the large meander-induced SST cooling. Analysis of the surface perturbation momentum budgets shows the importance of the pressure adjustment mechanism in surface wind response to the cold SST anomalies.

Validation of an ICP-OES method for macro and trace element determination in Laminaria and Porphyra seaweeds from four different countries

An Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) method for speedy simultaneous determination of 12 elements (Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) in seaweeds used as human food was optimized and then validated according to Eurachem guidelines. First, instrumental parameters (nebulizer argon flow rate and incident power) were optimized and then analytical lines free from spectral interferences were selected. The method was validated using biological Certified Reference Materials (CRMs). Intra- and inter-assay precision varied from 0.79% to 5.74% and from 2.48% to 8.57%, respectively, depending on the element studied. Within the experimental error, concentrations measured for each element coincided with certified values. Sensitivities, linearity and detection and quantification limits were also determined. Samples of seaweeds ( Porphyra and Laminaria) from France, Spain, Korea and Japan were analyzed by using the optimized and validated method. Some considerations on element composition of analyzed samples were made. Seaweeds from the Korean and Japanese coasts tended to display the highest concentrations of P and Al. In contrast, French Porphyra samples showed the lowest levels of Ba, Cu, Fe and Mn. Because great differences in element concentrations were observed due to costal origin and genus, any generalization regarding the algal mineral content may be considered misleading and scientifically inappropriate.

Polychlorinated Biphenyls and Their Hydroxylated Metabolites (OH-PCBs) in the Blood of Toothed and Baleen Whales Stranded along Japanese Coastal Waters

In this study, we determined the residue levels and patterns of polychlorinated biphenyls (PCBs) and hydroxylated PCBs (OH-PCBs) in the blood from eight species of toothed whales and three species of baleen whales stranded along the Japanese coast during 1999-2007. Penta- through hepta-chlorinated PCB congeners were the dominant homologue groups in all cetaceans. In contrast, specific differences in the distribution of dominant OH-PCB isomers and homologues were found among the cetacean species. In five species of toothed whales (melon-headed whale, Stejneger's beaked whale, Pacific white-sided dolphin, Blainville's beaked whale, and killer whale), the predominant homologues were OH-penta-PCBs followed by OH-tetra-PCBs and OH-tri-PCBs. The predominant homologues of finless porpoise and beluga whale were OH-penta-PCBs followed by OH-hexa-PCBs and OH-tri-PCBs. The predominant OH-PCB isomers were para-OH-PCBs such as 4OH-CB26, 4'OH-CB25/4'OH-CB26/4OH-CB31, 4OH-CB70, 4'OH-CB72, 4'OH-CB97, 4'OH-CB101/4'OH-CB120, and 4OH-CB107/4'OH-CB108 in toothed whales. In three baleen whales (common minke whale, Bryde's whale, and humpback whale) and in sperm whale (which is a toothed whale), OH-octa-PCB (4OH-CB202) was the predominant homologue group accounting for 40-80% of the total OH-PCB concentrations. The differences in concentrations and profiles of OH-PCBs may suggest species-specific diets, metabolic capability, and the transthyretin (TTR) binding specificity. These results reveal that the accumulation profiles of OH-PCBs in cetacean blood are entirely different from the profiles found in pinnipeds, polar bear, and humans.

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of 131I in brown algae was 0.37 ± 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of 131I and 137Cs in these seaweeds. The specific activity of 137Cs ranged from 0.0034 ± 0.00075 to 0.090 ± 0.014 Bq/kg-wet. Low specific activity and minimal variability of 137Cs in brown algae indicated that past nuclear weapon tests were the source of 137Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of 131I, there was no relationship between the sites where 131I was detected and the locations of nuclear power facilities. Most of the sites where 131I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of 131I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.

Amplification of tsunami heights by delayed rupture of great earthquakes along the Nankai trough

We investigated the effect of delayed rupture of great earthquakes along the Nankai trough on tsunami heights on the Japanese coast. As the tsunami source, we used a model of the 1707 Hoei earthquake, which consists of four segments: Tokai, Tonankai, and two Nankai segments. We first searched for the worst case, in terms of coastal tsunami heights, of rupture delay time on each segment, on the basis of superposition principle for the linear long wave theory. When the rupture starts on the Tonankai segment, followed by rupture on the Tokai segment 21 min later, as well as the eastern and western Nankai segments 15 and 28 min later, respectively, the average coastal tsunami height becomes the largest. To quantify the tsunami amplification, we compared the coastal tsunami heights from the delayed rupture with those from the simultaneous rupture model. Along the coasts of the sea of Hyu’uga and in the Bungo Channel, the tsunami heights become significantly amplified (>1.4 times larger) relative to the simultaneous rupture. Along the coasts of Tosa Bay and in the Kii Channel, the tsunami heights become amplified about 1.2 times. Along the coasts of the sea of Kumano and Ise Bay, and the western Enshu coast, the tsunami heights become slightly smaller for the delayed rupture. Along the eastern Enshu coast, the coast of Suruga Bay, and the west coast of Sagami Bay, the tsunami heights become amplified about 1.1 times.

Molecular analysis of green-tide-forming macroalgae in the Yellow Sea

In the summer of 2008, free-floating green algae bloomed in the Yellow Sea. Samples were collected in a wide area (119°32′–122°00′E, 32°25′–36°49′N). We calculated the sequence divergences of nuclear ITS, chloroplast rbcL, and psbA data of free-floating samples collected from the Yellow Sea and Ulvaceae from Europe and Japan. In the ITS sequence, 19 out of the 21 Yellow Sea samples of 2008 were identical to those of a sample taken at Qingdao in 2007. A low divergence (0.2%) was found in remaining two samples. Similar evidence was shown by pairwise distances of rbcL and psbA gene sequence data, implying the uniformity of the Yellow Sea blooms in 2007 and 2008. The ITS sequence of the Yellow Sea samples differed 8.1–10.8% from free-floating Enteromorpha or Ulva reported worldwide. ITS-based molecular phylogenetic results and rbcL sequence data grouped the free-floating alga in the Yellow Sea into one clade with Enteromorpha procera, Enteromorpha linza and Enteromorpha prolifera. Furthermore, both morphological characteristics and ribotype network of the ITS sequences imply that the blooming algae in 2007 and 2008 were E. prolifera. The haplotypes of the Yellow Sea free-floating E. prolifera are closely related to those from the Japanese coast but less to European and American algae.

Genetic evidence for parapatric differentiation of two forms of the brackish-water nereidid polychaete Hediste atoka

The phylogeography of local populations of the direct-developing estuarine polychaete Hediste atoka was examined by comparing the partial nucleotide sequences of the mitochondrial gene for cytochrome oxidase subunit I (COI) from 67 individuals collected from 27 sites that cover the majority of the distribution area of this species along the Japanese coasts, and from two sites of the Korean coasts. The phylogenetic trees drawn by four different methods (maximum likelihood, neighbor-joining, minimum evolution and maximum parsimony) showed consistently that populations of H. atoka could be divided into two parapatric forms: form A constituted all Korean and most Japanese populations except for those in southern Japan (southwestern Kyushu and the Ryukyu Islands), occupied by form B. No morphological differentiation has been detected between the two forms; the number of paragnath on the proboscis of each group was not significantly different from each other. The geographical distributions of these two forms did not overlap each other. These results suggest that cryptic speciation may occur in H. atoka.

海洋生物からの医薬シーズの探索

In search of new pharmaceutically valuable substances from marine organisms, we have been engaged in chemical studies 1] structural elucidation; 2] asymmetric total synthesis; 3] elucidation of pharmacophore by analysis of structure–activity relationship; 4] action mechanism and search for target protein on the bioactive substances, which were isolated from marine invertebrates and marine microorganisms at Japanese coasts and Indonesian coral reefs on the guidance of new practical bioassay. a) Anti–angiogenic substance: selective growth–inhibitor against human umbilical vein endothelial cells (HUVECs) (e.g. cortistatin A: 9(10–19)–abeo–androstane–type steroidal alkaloid having isoquinoline unit) b) Hypoxia–selective growth inhibitor: growth inhibitor against tumor cells under hypoxic environment selectively (e.g. furospinosulin–1: furanosesterterpene) c) Anti–mycobacterial substances, which are effective to both active and non–replicating persistent (NRP) states of tuberculosis (e.g. halicyclamine A: macrocyclic alkaloid)

Classification of fish schools based on evaluation of acoustic descriptor characteristics

Acoustic surveys were conducted from 2002 to 2006 in the East China Sea off the Japanese coast in order to develop a quantitative classification typology of a pelagic fish community and other co-occurring fishes based on acoustic descriptors. Acoustic data were postprocessed to detect and extract fish aggregations from echograms. Based on the expert visual examination of the echograms, detected schools were divided into three broad fish groups according to their schooling characteristics and ethological properties. Each fish school was described by a set of associated descriptors in order to objectively allocate each echo trace to its fish group. Two methods of supervised classification were employed, the discriminant function analysis (DFA) and the artificial neural network technique (ANN). We evaluated and compared the performance of both methods, which showed encouraging and about equally highly correct classification rates (ANN 87.6%; DFA 85.1%). In both techniques, positional and then morphological parameters were most important in discriminating among fish schools. Fish catch composition from midwater trawling validated the fish group classification through one representative example of each grouping. Both methods provided the essential information required for assessing fish stocks. Similar techniques of fish classification might be applicable to marine ecosystems with high pelagic fish diversity.