Miyakejima Research Articles

Three species of the family Aoridae Stebbing, 1899 (Crustacea: Amphipoda) collected from remote islands in southern Japan, with a key to all Japanese species of the family

Three species of the aorid amphipod were collected from remote islands in southern Japan. Protolembos ryukyuensis sp. nov. was collected from Ishigaki Island in Okinawa Prefecture and Tanegashima Island in Kagoshima Prefecture, and characterized by the dense plumose setae on the male gnathopods 1 and 2. Tethylembos cavatus sp. nov. and T. japonicus Ariyama, 2004 were collected from Miyake Island and the Ogasawara Islands in Tokyo Prefecture, respectively. Both species share the male gnathopod 1 propodus heavily setose medially; however, Tethylembos cavatus can be distinguished from T. japonicus in the excavated basis of the male pereopod 5. Keys to species of Protolembos Myers, 1988 and Tethylembos Myers, 1988 in the world and a key to all Japanese species of the family Aoridae are provided. Number of aorid species in Japan stands at 34.

Emergency Island Medical Care: Ⅱ. 2000 Miyake Island Mount Oyama Eruption

Emergency Island Medical Care: Ⅱ. 2000 Miyake Island Mount Oyama Eruption

Complete Genome Sequence of a Chemolithoautotrophic Iron-Oxidizing Bacterium, Acidithiobacillus ferrooxidans Strain NFP31, Isolated from Volcanic Ash Deposits on Miyake-Jima, Japan.

ABSTRACTThe genome sequence of Acidithiobacillus ferrooxidans strain NFP31, which is a chemolithoautotrophic iron-oxidizing bacterium that inhabits acidified volcanic deposits on Mount Oyama, Miyake Island (Miyake-jima), Japan, was determined to identify the genetic characteristics associated with pioneer microbes in newly placed pyroclastic deposits.

Photosynthetic Properties of Miscanthus condensatus at Volcanically Devastated Sites on Miyake-jima Island.

How photosynthetic-related leaf traits of non-nitrogen (N)-fixing pioneer species respond to extreme habitat conditions of primary succession is still not well-elucidated, especially in volcanically N-deplete habitats. The effect of N-deplete soil on photosynthetic-related leaf traits can provide a basis for predicting how plants adjust their strategies to adapt to such habitats. To examine the responses of leaf traits to extreme conditions, we investigated Miscanthus condensatus (a non-N-fixing C4 pioneer grass) which grows on a volcanically devastated area on Miyake-jima Island, Japan, in which the volcanic ash has been deposited for 17–18 years since the 2000-year eruption. Leaf N content (Narea), light-saturated photosynthetic rate (Amax), and photosynthetic N use efficiency (PNUE) in three contrasting study sites: bare land (BL), shrub land gap (SLG), and shrub land under canopy (SLUC) were determined. Results indicated that compared to previous studies and internal comparison of Miyake Island, M. condensatus in BL was able to maintain a relatively high Amax, Narea and PNUE. The higher Amax was in part a result of the higher PNUE. This is a characteristic necessary for its successful growth in N-deplete soils. These results suggest that M. condensatus has photosynthetic-related advantages for adaptation to volcanically N-deplete habitats.

Key Role of the Kuroshio Current in the Formation of Frontal Structure of an Extratropical Cyclone Associated with Heavy Precipitation

AbstractIn this study, the authors examined how the Kuroshio Current affected the frontal structure of an extratropical cyclone associated with heavy precipitation. We focused on an extratropical cyclone and related heavy precipitation on Miyake Island, which is situated near the Kuroshio Current, in January 2017. We first investigated the frontal structure and the attendant precipitation using observational data and objective analysis data. As the cyclone grew around the Kuroshio Current, a nonclassic front (outer front) intensified to the north of a warm front. A line‐shaped precipitation band developed along the outer front, contributing to the heavy precipitation on Miyake Island. The outer front lay along a sea surface temperature (SST) front associated with the Kuroshio Current in its early life stage. To clarify the impact of the SST front on the formation of the incipient outer front, we next conducted cloud‐resolving numerical experiments using SST distributions with and without the oceanic frontal structure. In the real SST experiment, sensible heat supply from the Kuroshio Current was large, while the amount from the ocean on the northern side of the warm current was small. This meridional difference in sensible heating caused frontogenesis along the SST front, which created the incipient front. Consequently, the real SST experiment reproduced the formation of the front. In contrast, the SST sensitivity experiments did not simulate such a sensible heating pattern or front formation. Thus, the Kuroshio Current played a key role in forming the incipient outer front and contributed to the heavy precipitation.

三宅島の噴火が島嶼(とうしょ)生態系に及ぼした影響と回復過程―生物間相互作用からみた三宅島の生態系の一側面―

三宅島の噴火が島嶼(とうしょ)生態系に及ぼした影響と回復過程―生物間相互作用からみた三宅島の生態系の一側面―

Interaction between insects and insect-pollinated plants on Miyake Island after a recent volcanic eruption: A comparison between vegetation types

In habitats after natural disturbance, mutualistic interaction between plant and flower-visiting insects is critical for maintenance and recovery of communities. However, the detailed characteristics of the plant-insect interactions that occur after a natural disturbance remain to be identified. We investigated the network structure of these interactions on the oceanic and volcanic island of Miyake, Japan. Large vegetated areas of this island were disturbed by a massive volcanic eruption during 2000. In 2012, we sampled insects visiting the flowering plants along the roadsides bordering six sites in the 3 vegetation types, which represent the island's vegetation after the volcanic disturbance; (1) shrubland colonizing accumulated ash (SL), (2) mature broad-leaved forests with partial damage (BF), and (3) coastal vegetation with partial damage (CV). Network properties, such as specialization, nestedness, and modularity did not differ among the three vegetation categories. We found the same specialized, modular, and anti-nested structures in five networks. The largest variation in insect/plant assemblages was observed between CV and the other vegetation types, but we did not find distinctive variations between SL and BF sites. Our study suggests that network structure is constant in the varying vegetation types, and raises the possibility that this island's mutualistic interactions are robust to volcanic disturbance.

RADARSAT determination of the outlines of the successively collapsing caldera at the Miyakejima 2000 eruption, Japan

RADARSAT determination of the outlines of the successively collapsing caldera at the Miyakejima 2000 eruption, Japan

Generation of periodic intrusions at Suruga Bay when the Kuroshio follows a large meandering path

We measured the vertical profiles of currents at the eastern mouth of the Suruga Bay using a moored acoustic Doppler current profiler (ADCP). Currents vertical profiles were found to be mostly barotropic in structure when intrusions occurred at the eastern mouth of the bay. Warm-water intrusions at the Suruga Bay and sea level elevations at the bay and at islands on the Izu Ridge located off the bay have the same period of 26 days. The temporal variation in the sea levels occurs in response to Kuroshio frontal waves, and the two phases are consistent. The sea level rise propagates from Hachijo Island to the Suruga Bay via Miyake Island and Kozu Island, i.e., from off the Suruga Bay to in or near the bay. The perturbation of the sea level along the Izu Ridge occurs as waves with a period of 26 days, a wavelength of 500km, and a phase speed of 23cm/sec. The propagated waves and those of the Kuroshio frontal waves have the same features. This means that the periodic inflows at the eastern mouth of the Suruga Bay are caused by the passage of Kuroshio frontal waves off the bay.

Nighttime Visits to Male Flowers of a Wild Grapevine by Some Oedemerid Beetles (Coleoptera: Oedemeridae) on Miyake Island

ABSTRACT: We report that some oedemerid beetles and longicorn beetles visited male flowers of the wild grapevine Vitis ficifolia var. izuinsularis on Miyake Island, off southeastern Honshu Island, Japan. We collected those beetles by beating inflorescences at night, though we had previously found no insects on the inflorescences in the daytime. We also used light traps to collect insects from the vicinity of inflorescences, and trapped many other insect species in addition to oedemerid beetles. Our results suggest that some oedemerid beetles are promising candidates as effective pollinators of the wild grapevine.

Rehabilitation from the long-term evacuations by disasters, Volcanic eruptions on Miyakejima Island and 311 disaster on "Fukushima"

Rehabilitation from the long-term evacuations by disasters, Volcanic eruptions on Miyakejima Island and 311 disaster on "Fukushima"

人工降雨観測実験に対する数値シミュレーション

人工降雨観測実験に対する数値シミュレーション

Recognition, opinion and evaluation of sabo by the residents around debris flow disaster stricken area in Miyake Island

Recognition, opinion and evaluation of sabo by the residents around debris flow disaster stricken area in Miyake Island

Effects of volcanic disturbance on the reproductive success of Eurya japonica and its reproductive mutualisms

Ecological observation of surviving organisms and their interactions during and after volcanic activity provides an indispensable opportunity to study how organisms respond to environmental devastation. Eurya japonica satisfies the criteria as a facilitator plant species in recovering forest on the volcanic Miyake Island, which erupted in 2000, because this species is more resistant to volcanic gases than other tree species on the island. We examined the effects of volcanic disturbance on reproductive success of E. japonica and compared the visitation frequencies of pollinator insects and frugivorous birds at nine sites showing different degrees of disturbance. The leaf health was strongly decreased by frequent volcanic gas exposure, whereas flower bud formation was not suppressed. The fruit abortion rate did not differ among sites, whereas the fruit set rate significantly decreased with increasing volcanic damage. The frequencies of pollinator and frugivorous bird visits were higher in heavily damaged areas. These results indicate that the pollination and seed-dispersal system of E. japonica was potentially maintained under volcanic disturbance, though the final reproductive success decreased.

三宅島近海流況観測とそれに基づく海流エネルギー資源量推定

Ocean current near Miyake Island was measured by an Acoustic Doppler Current Profiler equipped on a moored buoy system from March 2013 to March 2014 for an ocean current energy converter development project. Current variations associated with the Kuroshio,tide and wind,were found in the observed record and are described in the paper.Based on the Kuroshio axis location,periods with and without the Kuroshio intrusion into the island were identified. Spectral analysis of the current speed revealed that the diurnal variation is enhanced when the Kuroshio does not intrude.This enhancement of diurnal current variation is possibly related to the generation of the Island-Trapped Waves.By combining the fine-scale observation data and the long-term coarse-resolution Kuroshio axis data,inter-annual variability of the current power was estimated.The estimated current power is about three times larger than the one estimated from an ocean reanalysis.The result implies that coarse-resolution non-tidal numerical models possibly underestimate current power in coastal ocean.

Detection of microwave emission due to rock fracture as a new tool for geophysics: A field test at a volcano in Miyake Island, Japan

Abstract This paper describes a field test to verify a newly discovered phenomenon of microwave emission due to rock fracture in a volcano. The field test was carried out on Miyake Island, 150 km south of Tokyo. The main objective of the test was to investigate the applicability of the phenomenon to the study of geophysics, volcanology, and seismology by extending observations of this phenomenological occurrence from the laboratory to the natural field. We installed measuring systems for 300 MHz, 2 GHz, and 18 GHz-bands on the mountain top and mountain foot in order to discriminate local events from regional and global events. The systems include deliberate data subsystems that store slowly sampled data in the long term, and fast sampled data when triggered. We successfully obtained data from January to February 2008. During this period, characteristic microwave pulses were intermittently detected at 300 MHz. Two photographs taken before and after this period revealed that a considerably large-scale collapse occurred on the crater cliff. Moreover, seismograms obtained by nearby observatories strongly suggest that the crater subsidence occurred simultaneously with microwave signals on the same day during the observation period. For confirmation of the microwave emission caused by rock fracture, these microwave signals must be clearly discriminated from noise, interferences, and other disturbances. We carefully discriminated the microwave data taken at the mountaintop and foot, checked the lightning strike data around the island, and consequently concluded that these microwave signals could not be attributed to lightning. Artificial interferences were discriminated by the nature of their waveforms. Thus, we inferred that the signals detected at 300 MHz were due to rock fractures during cliff collapses. This result may provide a useful new tool for geoscientists and for the mitigation of natural hazards.

Dual layer structural thermoplastic polyester powder coating film and its weathering resistance

AbstractMicro FTIR analysis was performed to the point with a 50–80 μm spatial resolution to verify the exact structure of a new blend thermoplastic powder coating film. Resistance to certain artificially accelerated conditions and actual outdoor exposure were examined to confirm the performance of the film as a protective coating for use in the telecommunication field. The new blend powder coating film consists of primary polyethylene terephthalate (PET) and secondary polyvinyl butyral (PVB) resins, and has a distinct dual phase structure. Specifically, it forms a continuous PVB phase in a surface layer with a thickness of approximately 100–150 μm. Good corrosion resistance was confirmed in artificially accelerated testing using salt water spray, heat cycle, and accelerated UV tests. Actual outdoor exposure in a metropolitan area (Shinkiba in Tokyo) and a coastal area (Miyake Island) revealed good weathering performance throughout the study period. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Elution behaviour and environmental impact of heavy metals and rare-earth elements from volcanic ashes of Mt. Oyama, Miyake Island

To obtain information on the environmental impact of materials eluted from volcanic ashes of Mt. Oyama, Miyake Island, which erupted in July 2000, the dissolution behaviours of heavy metals and rare-earth elements from the volcanic ashes were examined. The most important characteristic of the Mt. Oyama eruption is that sulphur dioxide (SO2) gas has been continuously released, and all persons living on Miyake Island have been required to evacuate. To estimate in terms of the volcanic eruption using SO2 gas, the ash nature in Mt. Usu, Hokkaido, was also examined and compared with that in Mt. Oyama. When rain water mixed the ashes, the water from the ashes of Mt. Oyama became acidic because of the sulphuric acid. Therefore, SO2 gas in Mt. Oyama can accelerate the dissolution of protons and heavy metals in the ashes, whereas the rain water in Mt. Usu was not acidic and the dissolution of the heavy metals was not so evident compared with that in the case of Mt. Oyama. With this sulphuric acid, heavy metals such as As, Cd, Pb and Hg in the ashes in Mt. Oyama easily dissolved owing to the low pH. The ashes in Mt. Oyama had been released for eight years and the amount of fallen ashes was estimated to be 33 billion tons. The weights of the harmful heavy metals in the volcanic ashes, such as As, Cd, Pb and Hg, were estimated to be 3.8 × 102, 1.3 × 103, 1.1 × 103 and 29 kg, respectively, and these heavy metals were dissolved and diluted in seawater. Therefore, the concentration and species (chemical form) of these metals should be carefully monitored in the future. Moreover, SO2 gas, which has a direct effect on human health and has been monitored continuously, causes other effects, such as facilitation of metal ion elution and rock aeration.

Real-time Simulation and Analysis on Long-range Atmospheric Dispersions of Volcanic Gases Discharged from the Miyake Island

Real-time Simulation and Analysis on Long-range Atmospheric Dispersions of Volcanic Gases Discharged from the Miyake Island

Development of a Chemical Transport Model Coupled with a Mesoscale Meteorological Model and Application to Atmospheric Diffusion of Volcanic Gases from Miyake Island

Development of a Chemical Transport Model Coupled with a Mesoscale Meteorological Model and Application to Atmospheric Diffusion of Volcanic Gases from Miyake Island