Environmental and Economic Recovery Post-Fukushima Daiichi Nuclear Disaster: Isotope Characteristics and the Recovery of a Crippled Fisheries Industry

The 2011 Tohoku earthquake and subsequent tsunami had a catastrophic effect on the aquaculture industry of the North-East Japanese coast. Ten years on, this paper examines the environmental and economic impacts of this disaster within the context of the Fukushima nuclear meltdown. Following structural damage to the Tokyo Electric Power Company Fukushima Daiichi plant, fisheries and aquaculture industries were suspended, given the initially high radio caesium output into the coastal water column. Daily radiation testing began on all fisheries products, with tentative industry resuming within the Fukushima prefecture once radiation had dropped below the 50 Bq/kg, as stipulated by the Fukushima Fisheries Association. Routine testing continues biweekly (at least until March 2021). As of May 2016, 73 fish species were passed for consumption. The rapid functional recovery of the fisheries industry has been mediated by two factors, the sedimentation characteristics of the caesium isotopes and deposition of isotopes out to sea in an Easterly direction, given the interaction of oceanic currents. While the aquaculture industry may have recovered and food reduced to safe radiation levels, the disaster continues to exert a domestic and international economic impact given the stigma of Fukushima radiation.

Rapid Assessment of Tsunami Offshore Propagation and Inundation with D-FLOW Flexible Mesh and SFINCS for the 2011 Tōhoku Tsunami in Japan

This study demonstrates the skills of D-FLOW Flexible Mesh (FM) and SFINCS (Super-Fast INundation of CoastS) in combination with the Delft Dashboard Tsunami Toolbox to numerically simulate tsunami offshore propagation and inundation based on the example of the 2011 Tōhoku tsunami in Japan. Caused by a megathrust earthquake, this is one of the most severe tsunami events in recent history, resulting in vast inundation and devastation of the Japanese coast. The comparison of the simulated with the measured offshore water levels at four DART buoys located in the Northwestern Pacific Ocean shows that especially the FM but also the SFINCS model accurately reproduce the observed tsunami propagation. The inundation observed at the Sendai coast is well reproduced by both models. All in all, the model outcomes are consistent with the findings gained in earlier simulation studies. Depending on the specific needs of future tsunami simulations, different possibilities for the application of both models are conceivable: (i) the exclusive use of FM to achieve high accuracy of the tsunami offshore propagation, with the option to use an all-in-one model domain (no nesting required) and to add tsunami sediment dynamics, (ii) the combined use of FM for the accurate simulation of the tsunami propagation and of SFINCS for the accurate and time efficient simulation of the onshore inundation and (iii) the exclusive use of SFINCS to get a reliable picture of the tsunami propagation and accurate results for the onshore inundation within seconds of computational time. This manuscript demonstrates the suitability of FM and SFINCS for the rapid and reliable assessment of tsunami propagation and inundation and discusses use cases of the three model combinations that form an important base for tsunami risk management.

THE JAPANESE COAST GUARD’S OPERATIONALIZED HEDGING STRATEGY IN THE EAST CHINA SEA

Qualitative evidence from nearly two dozen sources are used to explain how and why an energized, retooled, and restructured Japanese Coast Guard can serve as the primary enabler of an updated Japanese maritime security policy. This study examines the efforts associated with improving Japan’s maritime security in the East China Sea against the pressure points of an assertive Chinese naval apparatus, as well as the country’s enduring security partnership with the U.S. This research showcases both how, and more importantly, why, a specific Japanese Coast Guard-related policy and operational capability can be effective when developed and cultivated from a tailored hedging strategy. This study finds Japan’s best bet for long-term stability and absolute security gain lies in operationalizing a varied hedging strategy through a capable and resourced coast guard.

Correlation between Polycyclic Aromatic Hydrocarbons in Wharf Roach (Ligia spp.) and Environmental Components of the Intertidal and Supralittoral Zone along the Japanese Coast

Polycyclic aromatic hydrocarbon (PAH) concentrations in wharf roach (Ligia spp.), as an environmental indicator, and in environmental components of the intertidal and supralittoral zones were determined, and the PAH exposure pathways in wharf roach were estimated. Wharf roaches, mussels, and environmental media (water, soil and sand, and drifting seaweed) were collected from 12 sites in Japan along coastal areas of the Sea of Japan. PAH concentrations in wharf roaches were higher than those in mussels (median total of 15 PAHs: 48.5 and 39.9 ng/g-dry weight (dw), respectively) except for samples from Ishikawa (wharf roach: 47.9 ng/g-dw; mussel: 132 ng/g-dw). The highest total PAH concentration in wharf roach was from Akita (96.0 ng/g-dw), followed by a sample from Niigata (85.2 ng/g-dw). Diagnostic ratio analysis showed that nearly all PAHs in soil and sand were of petrogenic origin. Based on a correlation analysis of PAH concentrations between wharf roach and the environmental components, wharf roach exposure to three- and four-ring PAHs was likely from food (drifting seaweed) and from soil and sand, whereas exposure to four- and five-ring PAHs was from several environmental components. These findings suggest that the wharf roach can be used to monitor PAH pollution in the supralittoral zone and in the intertidal zone.

EVALUATION OF VEGETATED DUNES FOR EROSION RESISTANCE AGAINST TSUNAMI OVERFLOW

A total of 14 soil samples were collected from sand dunes without scattering, and the process of tsunami-induced erosion was observed using hydraulic model experiments. The densities of vegetation roots were measured at 45 points on seven beaches along the Japanese coast. The results of the experiment confirmed that the roots of vegetation highly affected the resistance of soil against erosion. Based on this result, an erosion model based on the index alpha was proposed, and the relationship between alpha and root density was described. Then, the applicability of the proposed erosion model was investigated using numerical simulations.

New seriated Amathia species in Japan, with a redescription of A. acervata Lamouroux, 1824 (Bryozoa: Ctenostomata)

The status of seriated Amathia species (Bryozoa: Ctenostomata) in Japan is reviewed. Several historical specimens and materials recently collected from several localities along the Japanese coast are examined in this study. Amathia acervata Lamouroux, 1824, collected from Japan by Wilhelm Gottlieb Tilesius in 1804, was examined and is redescribed from a reconstituted fragment of the sole type specimen. Material previously reported from Wakayama Prefecture is very similar to Amathia acervata, but differs in having fewer autozooid pairs per cluster, which spiral in different directions; the species is described as a new species Amathia brevisilva n. sp. Measurements of colony characters vary according to the effects of fixation, but stolon length, the ratio of autozooid clusters on stolons, spirality and pigmentation are useful characters for the identification of Japanese seriated Amathia. In addition, two new species are described, Amathia reptopinnata n. sp. and Amathia fimbria n. sp. Amathia reptopinnata n. sp. is characterized by its robust form, dark colour, dichotomous branching, long stolons, long autozooidal clusters and pinnately arranged prostrate zooids. Amathia fimbria n. sp. was found only in the Showa Emperor collection, and is characterized by its compact colony form, remarkably short internode length and trichotomous branching.

Two new species of the genus Caligus (Crustacea, Copepoda, Siphonostomatoida) from the Sea of Japan, with a note on the establishment of a new species group

Two new species of Caligus are described from the Japanese coast of the Sea of Japan. Caligus chinglonglinisp. nov. is based on a male specimen found in a plankton sample, whereas C. kajiisp. nov. was collected from the body surface of the host flathead Platycephalus sp. These two new species can be assigned to a distinct species group, the pseudorhombi group newly named and defined by the morphology of the genital complex in both sexes, and by the structure and armature of legs 2 and 4. The species group so far accommodates 19 species including these two new species. The morphology, host specificity and zoogeography of the species group are discussed herein and keys to species groups of Caligus and to species of the C. pseudorhombi species group are provided.

Tsunami Risk in Japanese Coast and Recent Mitigation Technique using Removable Breakwater

In this paper, the tsunami risk in the west coast of Japan is introduced. Especially, the inundation risk in Osaka city is discussed. Three visor gates are installed at the mouths of main rivers in the city. The gates are mainly installed to prevent the storm surge due to typhoons but they are effective to reduce the tsunami height at the mouth point of river. Though the gates are necessary to prevent the tsunami inundation, the stability against tsunami forces is not enough because the gates were constructed in 1960s. Therefore, the removable breakwater is now under consideration to reduce the tsunami force. The hydraulic experiment was carried out in order to investigate the applicability of the removable breakwater. The reduction rate by the breakwater was derived from the experiment.