Japanese Coast Research Articles

Construction of Climate Change-Adapted Seaweed Beds on the Japanese Coast

Miura, H.; Ito, Y., and Suenaga, Y., 2018. Construction of Climate Change-Adapted Seaweed Beds on the Japanese Coast. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 391–395. Coconut Creek (Florida), ISSN 0749-0208.Japanese coastal seaweed beds are experiencing a long-term decline in area coverage in a phenomenon called isoyake, which has massively impacted the fisheries industry. Therefore, research has been performed on seaweed bed restoration. Consequent measures have been implemented along with the promulgation of relevant technology. Meanwhile, increasing seawater temperatures and other environmental changes associated with climate change, which is one of the causes of isoyake, are spreading globally and have become increasingly severe in recent years. With respect to methods of coping with the effects of climate change, the Intergovernmental Panel on Climate Change's Fifth Assessment Report (2014) calls for “adaptation” to effects that have already occurred and unavoidable medium- and long-term effects. In this context, this paper discusses the present state of and future forecasts for seaweed beds on the Japanese coast, and it then considers the future trends of climate change-adapted seaweed bed construction.

Genetic diversity and population structure of penis fish (Urechis unicinctus) based on mitochondrial and nuclear gene markers

Urechis unicinctus is distributed only in Bohai Gulf of China and Korean and Japanese coast. The wild populations of this species have sharply declined in China and Japan. We collected 105 samples from six localities of Bohai Gulf and Korea coast, and investigated genetic diversity and population structure with mitochondrial COI, 16S-rRNA and nuclear 28S-rRNA gene fragments. Genetic diversity of U. unicinctus based on COI sequences was still high (Hd: 0.9595, π: 0.0101), however, 28S-rRNA gene sequences showed low level of genetic diversity (Hd: 0.4084, π: 0.0007). Based on COI sequences, FST values between populations ranged from −0.00204 to 0.05210, and 99.12% genetic diversity was contributed by different individuals within population. Both phylogenetic trees and median-joining network did not show clear geographic cluster, haplotypes from different populations were mixed. Our results indicated low level of genetic divergence among different localities of U. unicinctus, and this species should be treated as a whole population among China, Japan and Korea coast during species conservation.

Analysis of functional components and radical scavenging activity of 21 algae species collected from the Japanese coast

The functional chemical substances and the antioxidant activity of lipids in 21 marine algae along the Japanese coast were investigated. Principal component analysis was performed to detect any correlation between the chemical substances and algae phylum. Chlorophyta contained a high level of β-carotene. Rhodophyta contained high amounts of cholesterol, β-sitosterol, and saturated fatty acids. Phaeophyta were rich in fucosterol, α-tocopherol, fucoxanthin, and polyphenol. Phaeophyta algae also showed the highest antioxidant activity compared with other phylum. This suggests that Phaeophyta has the greatest potential to be used as a functional food. Consumption of the beneficial Phaeophyta species, such as Eisenia arborea Areschoug and Ecklonia cava Kjellman should be encouraged as not only as food products but also as nutraceuticals and dietary supplements. These beneficial ingredients should be encouraged to be studied in depth with the possibility to develop specific formulated products target to special consumer’s population with added nutritional value.

High-resolution modeling of the Kuroshio current power south of Japan

Ocean current power near the Japanese coast was estimated using a high-resolution, three-dimensional ocean model. Two experiments were conducted to distinguish the impact of the Kuroshio large meander. The simulation results were validated by comparison with measurements. To choose the proper site for ocean current power generation experiment, we quantitatively analyzed the variation of the current field for three candidate areas: around the Tokara Strait, south of Cape Ashizuri (AS), and south of Cape Shionomisaki (SH). The results show that the current around the Tokara Strait is the weakest among the three candidates. The current south of SH is strongest for the non-large-meander period. The area south of AS is promising for ocean current power generation, because the current is stable and strong regardless of the large meander, and the average ocean current power density can reach 1 \(\hbox {kW/m}^{2}\).

Transition of the Tsushima Warm Current Path Observed over Toyama Trough, Japan

AbstractMooring, CTD, and ADCP observations were made in 2012 in and around the Toyama Trough (TT) cutting across a continental shelf along the Japanese coast of the Japan Sea between Noto Peninsula (NP) and Sado Island (SI) to investigate spatiotemporal characteristics of path transition of the coastal branch of the Tsushima Warm Current (CBTWC). Around SI, downstream of the TT boundary, a wavelike alongshore current perturbation, accompanied by sea level rise, was observed. This perturbation occurred after the seasonal amplification of the CBTWC around the NP on the upstream boundary of the TT. This process was delineated by the results of numerical experiments performed with a two-layer model using idealized topography. The model showed that a current path of the CBTWC shifted from alongshore mode to offshore mode bridged over the TT in association with the lee eddy development behind the NP toward the SI over the TT. This lee eddy is generated by positive vorticity induced over topographic discontinuity between the continental shelf off the northern coast of the NP and deeper region of the TT. The model indicated the period of eddy formation is 60–90 days if the volume transport is 1 Sv (1 Sv ≡ 106 m3 s−1), whereas the observations showed the formation period was only 47 days at 1.2 Sv of volume transport. To explain this discrepancy, temporal variation of the CBTWC, vortex supply from preexisting eddies, or eddies caused by the scattering of coastal-trapped waves were suggested as new processes that accelerate the growth rate of the lee eddy.

Theoretical Solution and Applications of Ocean Bottom Pressure Induced by Seismic Seafloor Motion

AbstractSeismic signals captured by ocean bottom pressure sensors, which are designed to record tsunami waves, are largely ignored. In this paper, we derive a simple theoretical solution of the ocean bottom pressure as a function of prescribed seafloor motion. All the assumptions are clearly stated and analyzed. The solution is checked by comparing the seafloor displacement and pressure from three M7+ earthquakes, recorded by ocean bottom seismometers and pressure gauges located off the Japanese coast. We then show two applications. First, using the seafloor displacement data recorded by an ocean bottom seismometer, the pressure amplitude recorded by the associated pressure gauge is corrected, and vice versa. Second, pressure recordings from Deep Ocean Assessment and Reporting of Tsunamis during the 2011 Tohoku earthquake are converted to seafloor displacements, which are then utilized to estimate the earthquake focal mechanism. Thus, we demonstrate that seismic signals recorded by pressure sensors have great potential for fast estimate of earthquake source parameters.

Population panmixia and demographic expansion of a highly piscivorous marine fish Scomberomorus niphonius.

Population structure and demographic history of the Japanese Spanish mackerel Scomberomorus niphonius a highly piscivorous and migratory marine fish, were assessed using mitochondrial DNA control region sequences (n = 720) and microsatellite genotypes at five loci (n = 1331) for samples collected on Japanese coasts from 2001 to 2010. The population structure was panmictic and the haplotype and allele frequencies were temporally stable even during the recent recovery process. Demographic expansion was strongly supported throughout the Pleistocene, suggesting that the oscillating glacial and interglacial climate conditions in the Pleistocene had no substantial impact on the demographic history of S. niphonius.

Temporal and spatial changes in the copepod community during the 1974–1998 spring seasons in the Kuroshio region; a time period of profound changes in pelagic fish populations

The long-term change (1974–1998) of the pelagic copepod community in the Kuroshio region, western Pacific was examined in archival samples collected both day and night in April/May in a time period of profound changes in the pelagic fish populations. A total of 162 adult copepod species was found. The community analysis based on species composition and abundance of adult copepods identified five assemblages (A–E) by cluster analysis. These assemblages were distributed in the north-frontal area of the Kuroshio Current within the slope area (A), the Kuroshio axis area (B), the subtropical area (C, D), and the coastal area within the slope area (E), indicating that such diverse communities were formed to correspond with the gradual change in the oceanic environment across the Kuroshio Current. The abundance of copepods in the north-frontal area of the Kuroshio Current (A) was 1.6 times greater than that of the other assemblages. Kuroshio/subtropical species were abundant in the assemblage, suggesting that these species that were transported from the Kuroshio and/or subtropical regions increased in the slope region. Abundance and species richness of two assemblages (C, D), which were found in the subtropical areas were higher at night (C) than during the day (D), suggesting that diel vertical migration of copepods is one of the most important factors affecting changes in the community. Furthermore, a generalized additive model revealed that the most dominant subtropical/Kuroshio species increased in years in which the Kuroshio Current flowed further south, with the Kuroshio axis located far from the Japanese coast. In contrast, the model showed that the lower latitude of the Kuroshio axis positioned negatively affected coastal-dominant species, such as Paracalanus parvus sensu lato (s.l.). These results indicate that onshore-offshore shifts of the Kuroshio axis caused by Kuroshio meandering was an important factor involved in the inter-annual change in the copepod community during April–May in the Kuroshio region, suggesting that the inter-annual change of copepod communities might affect survival and growth rates of larvae in pelagic migratory fish which utilize the Kuroshio region as spawning and nursery grounds.

Sea Level Variability around Japan during the Twentieth Century Simulated by a Regional Ocean Model

Sea level variability around Japan from 1906 to 2010 is examined using a regional ocean model, along with observational data and the CMIP5 historical simulations. The regional model reproduces observed interdecadal sea level variability, for example, high sea level around 1950, low sea level in the 1970s, and sea level rise during the most recent three decades, along the Japanese coast. Sensitivity runs reveal that the high sea level around 1950 was induced by the wind stress curl changes over the North Pacific, characterized by a weakening of the Aleutian low. In contrast, the recent sea level rise is primarily caused by heat and freshwater flux forcings. That the wind-induced sea level rise along the Japanese coast around 1950 is as large as the recent sea level rise highlights the importance of natural variability in understanding regional sea level change on interdecadal time scales.

Fate of microplastics and mesoplastics carried by surface currents and wind waves: A numerical model approach in the Sea of Japan

A numerical model was established to reproduce the oceanic transport processes of microplastics and mesoplastics in the Sea of Japan. A particle tracking model, where surface ocean currents were given by a combination of a reanalysis ocean current product and Stokes drift computed separately by a wave model, simulated particle movement. The model results corresponded with the field survey. Modeled results indicated the micro- and mesoplastics are moved northeastward by the Tsushima Current. Subsequently, Stokes drift selectively moves mesoplastics during winter toward the Japanese coast, resulting in increased contributions of mesoplastics south of 39°N. Additionally, Stokes drift also transports micro- and mesoplastics out to the sea area south of the subpolar front where the northeastward Tsushima Current carries them into the open ocean via the Tsugaru and Soya straits. Average transit time of modeled particles in the Sea of Japan is drastically reduced when including Stokes drift in the model.

4-1-1 越波式波力発電装置開発に向けたわが国の波エネルギー賦存量と地域特性(4-1 海洋エネルギー,Session 4 新エネルギー)

4-1-1 越波式波力発電装置開発に向けたわが国の波エネルギー賦存量と地域特性(4-1 海洋エネルギー,Session 4 新エネルギー)

Methodology to Improve Corrosion Rate Estimation Based on Atmospheric Corrosion Monitoring Sensors

The accuracy of corrosion rate estimation using atmospheric corrosion monitoring (ACM) sensors is improved using humidity data. This methodology determines the daily amount of sea salt, Ws, to consecutively determine rain/dew/dry conditions for instantaneous output. ACM outputs observed in 4.8-m-long steel pipe braces installed on the Japanese coast were used to verify the methodology. Ws is the basic value used in analysis and is in agreement with experimental observations. When using this methodology, divergence of estimated and observed corrosion rates was reduced by up to 40% compared with results using the conventional methodology that determines rainfall using only outputs from ACM sensors.

Cotyledon morphology of Convolvulaceae seedling from sea-borne seeds on the Japanese coast

Cotyledon morphology of Convolvulaceae seedling from sea-borne seeds on the Japanese coast

Detecting the Early Genetic Effects of Habitat Degradation in Small Size Remnant Populations ofMachilus thunbergiiSieb. et Zucc. (Lauraceae)

Habitat degradation caused by human activities has reduced the sizes of many plant populations worldwide, generally with negative genetic impacts. However, detecting such impacts in tree species is not easy because trees have long life spans.Machilus thunbergiiSieb. et Zucc. (Lauraceae) is a dominant tree species of broad-leaved evergreen forests distributed primarily along the Japanese coast. Inland habitats for this species have become degraded by human activities. To investigate the effects of habitat degradation on genetic structure, we compared the genetic diversities of mature and juvenile trees of fiveM. thunbergiipopulations around Lake Biwa in Japan. Allelic diversity was influenced by past lineage admixture events, but the effects of forest size were not clear. On the other hand, the inbreeding coefficient of the juvenile stage was higher in small populations, whereas large populations maintained panmictic breeding. Also, the extent of genetic differentiation was greater in juveniles than in mature trees. We detected the early genetic effects of habitat degradation in small, isolatedM. thunbergiipopulations, indicating that habitat degradation increases inbreeding and genetic differentiation between populations.

Population- and growth-related differences in helminthic fauna of finless porpoises (Neophocaena asiaeorientalis) in five Japanese populations.

A survey of helminths and ectoparasites, including epizoits, was conducted in narrow-ridged finless porpoises (Neophocaena asiaeorientalis) from Japanese five populations using dead stranded or incidentally caught animals. In total, 13 helminth species were found (6 nematodes, 4 trematodes, 2 cestodes and 1 acanthocephalan) in 137 porpoises. A new location record of Stenurus nanjingensis and a new host record of Tetrabothrius sp. were obtained. Eight species of helminth were considered common in the Japanese populations of the finless porpoise: Pharurus sunameri, Pharurus asiaeorientalis, Nasitrema spathulatum, Nasitrema sunameri, Halocercus pingi, Halocercus sunameri, Campula oblonga and Synthesium elongatum. No anisakid nematodes were found. N. spathulatum was found only in the western waters of the Seto Inland Sea. Low prevalence of C. oblonga in the Omura Bay was demonstrated. H. pingi was mostly found in very young porpoises before starting to eat prey, indicating prenatal or transmammary infection. However, a congeneric species, H. sunameri, mainly infected weaned porpoises, indicating that these two species possess different transmission pathways. This study provides information on the geographical distribution and prevalence of helminth parasites in finless porpoises off the Japanese coast.

A new species of the genusHalectinosoma(Copepoda, Harpacticoida, Ectinosomatidae) from Korea

Abstract A new species of harpacticoid copepod, Halectinosoma foveolata, was described from sandy sediments on several intertidal areas of Korea. This new species is mostly similar to H. dimorphum Coull, 1970, but differs from the latter by the following characteristics combined: (1) the third segment of antennule is longest; (2) the first exopodal segment of antenna has a row of spinules; (3) the mandibular gnathobase is composed of chitinous teeth without dorsal seta; (4) the female P5 has an incomplete boundary between the exopod and the baseoendopod; (5) the female P5 baseoendopod has two rows of spinules. We also discuss the state of H. arenicola sensu Ito (1973), reported from the Japanese coast, which is considered here a synonym with the new species.

Reexamination of the magnitudes for the 1906 and 1922 Chilean earthquakes using Japanese tsunami amplitudes: Implications for source depth constraints

AbstractFar‐field tsunami records from the Japanese tide gauge network allow the reexamination of the moment magnitudes (Mw) for the 1906 and 1922 Chilean earthquakes, which to date rely on limited information mainly from seismological observations alone. Tide gauges along the Japanese coast provide extensive records of tsunamis triggered by six great (Mw >8) Chilean earthquakes with instrumentally determined moment magnitudes. These tsunami records are used to explore the dependence of tsunami amplitudes in Japan on the parent earthquake magnitude of Chilean origin. Using the resulting regression parameters together with tide gauge amplitudes measured in Japan we estimate apparent moment magnitudes of Mw 8.0–8.2 and Mw 8.5–8.6 for the 1906 central and 1922 north‐central Chile earthquakes. The large discrepancy of the 1906 magnitude estimated from the tsunami observed in Japan as compared with those previously determined from seismic waves (Ms 8.4) suggests a deeper than average source with reduced tsunami excitation. A deep dislocation along the Chilean megathrust would favor uplift of the coast rather than beneath the sea, giving rise to a smaller tsunami and producing effects consistent with those observed in 1906. The 1922 magnitude inferred from far‐field tsunami amplitudes appear to better explain the large extent of damage and the destructive tsunami that were locally observed following the earthquake than the lower seismic magnitudes (Ms 8.3) that were likely affected by the well‐known saturation effects. Thus, a repeat of the large 1922 earthquake poses seismic and tsunami hazards in a region identified as a mature seismic gap.

Recirculation of FNPP1-derived radiocaesium observed in winter 2015/2016 in coastal regions of Japan

We conducted enhanced surface water sampling at more than 80 stations in coastal regions on both the Japan Sea and Pacific Ocean sides of Japan in winter 2015/2016 to examine the recirculation behaviour of FNPP1-derived radiocaesium in the surface layer 5 years after the 2011 FNPP1 accident. We found that a small part of the FNPP1-derived radiocaesium had already recirculated in the surface layer and reached the Japanese coast.

A new record of the Axiid shrimp Balssaxius habereri (Balss, 1913) (Crustacea: Decapoda: Axiidea) in Korean waters

Balssaxius habereri (Balss, 1903) has been newly reported in Korean waters. This species was previously known from the Pacific coast of northern Japan, Korea Strait, Yellow Sea, and Japanese coast of the East Sea. Specimens were collected from western Jeju Island using otter trawls at depths of 65–85 m. Regarding Korean axiid shrimps, a single species, Boasaxius princeps (Boas, 1880), previously known as Axiopsis princeps in Korea, has been recorded. B. habereri is easily distinguished from B. princeps as it does not have tufts of setae on its body and males do not have the first pleopod. Morphological descriptions and color photos of the specimens are provided.

Zoanthamine-Type Alkaloids from the Zoanthid Zoanthus kuroshio Collected in Taiwan and Their Effects on Inflammation.

Zoanthus kuroshio is a colorful zoanthid with a fluorescent pink oral disc and brown tentacles, which dominates certain parts of the Taiwanese and Japanese coasts. This sea anemone is a rich source of biologically active alkaloids. In the current investigation, two novel halogenated zoanthamines [5α-iodozoanthenamine (1) and 11β-chloro-11-deoxykuroshine A (2)], along with four new zoanthamines [18-epi-kuroshine A (3), 7α-hydroxykuroshine E (4), 5α-methoxykuroshine E (5), and 18-epi-kuroshine E (6)], and six known compounds were isolated from Z. kuroshio. Compounds 1 and 2 are the first examples of halogenated zoanthamine-type alkaloids isolated from nature. Compounds 3 and 6 are the first zoanthamine stereoisomers with a cis-junction of the A/B rings. All isolated compounds were evaluated for their anti-inflammatory activities by measuring their effects on superoxide anion generation and elastase release by human neutrophils in response to fMLP.