Kume Island Research Articles

Using contingent behaviour analysis to estimate benefits from coral reefs in Kume Island, Japan: A Poisson‐inverse Gaussian approach with on‐site correction

AbstractCoral reefs face a critical crisis worldwide because of rising ocean temperature, excessive use of resources and soil erosion. As reefs have great recreational and tourism value, the degradation of their quality may have a significant effect on tourism. This study employs a contingent behaviour approach to estimate the effect of reef extinction on the recreational demand for Kume Island, Okinawa, Japan. We propose a Poisson‐inverse Gaussian (PIG) model with correction for on‐site sampling issues to derive a more accurate estimate of consumer surplus (CS). The results show that the annual CS per‐person trip is 5898 yen (US$ 49.15 in 2015 currency) according to the random‐effects PIG model.

Priority sites for coral aquaculture in Kume Island based on numerical simulation

Global and local stresses such as increased water temperature and terrestrial sediment runoff significantly affect coral reef ecosystems. Over the past three decades, the increase in the intensity and frequency of coral bleaching has been a significant problem in tropical and subtropical coastal seas, and maintaining healthy coral reef ecosystems has long been a challenge. Coral cover in Shimajiri Bay on Kume Island, located in the Nansei Islands (Okinawa Prefecture, southern Japan), has declined due to exposure to high water temperatures, an outbreak of coral predators, and sediment (red soil) inflow from the land. From such a background, coral aquaculture has been implemented at a few stations in the bay. Therefore, it is essential to conduct aquaculture in suitable locations for coral growth and survival. This study aimed to select suitable locations for coral culture with high spatial resolution in an enclosed bay that was greatly affected by red soil runoff, mainly from a sugarcane field. A freshwater and red soil runoff model for the watershed was merged with a coastal hydrodynamic, red soil dispersal, and accumulation model at a spatial resolution of 75 m for Shimajiri Bay. The simulation results were validated using in situ continuous and routine observations. Simulations were conducted over ten years. Locations not subjected to high water temperature in the bay or river loading were selected based on topography, simulated water temperature, salinity, and red soil content of sea sediment. This coupled model enables us to evaluate the growth and survival conditions of cultured corals with high spatiotemporal resolution and quantitatively consider the reduction target of red soil runoff to realize robust coral growth and survival.

The folk beliefs and the number of children of the elderly of Kume Island, Okinawa, Japan

The folk beliefs and the number of children of the elderly of Kume Island, Okinawa, Japan

Chironomidae collected at the seashore in Kume Island, Japan

Local residents and tourists of Kume Island suffer from the biting of Leptoconops taiwanensis (Lien, Lin & Weng 1998) (Ceratopogonidae), a species known as asa-mushi (sea lettuce bug). Because L. taiwanensis bites tend to occur while harvesting sea lettuce, some locals mistakenly believe that L. taiwanensis inhabits the sea lettuce. The objectives of the current study are to (i) identify the chironomid species inhabiting the sea lettuce, (ii) determine the distribution of the larvae, and (iii) perform a faunistic investigation of Chironomidae at Shinri Beach. Only one male chironomid species, Ainuyusurika tuberculatum (Tokunaga, 1940), emerged from the samples taken from the beach. The density of chironomid larvae was the highest in the presence of sea lettuce. A total of 53 males were collected using light traps, of which we identified males of seven genera and seven species belonging to three subfamilies. No L. taiwanensis were collected in this study.

A novel aromatic compound from the fungus Synnemellisia sp. FKR-0921.

The filamentous fungus Synnemellisia sp. strain FKR-0921 was obtained from soil collected on Kume Island, Okinawa. The MeOH extract of FKR-0921 cultured on a solid rice medium yielded a new aromatic compound, synnemellisitriol A (1). The structure, including the absolute configuration, was elucidated by spectroscopic analysis (FT-IR, NMR, and HR-ESI-MS), and the absolute configuration at C-9 of 1 was determined using the modified Mosher's method. Additionally, 1 was evaluated for its biological activities, including metallo-β-lactamase inhibitory activity, type III secretion system inhibitory activity, antimicrobial activity, antimalarial activity, and cytotoxicity.

Genome‐wide SNP genotyping reveals hidden population structure of an acroporid species at a subtropical coral island: Implications for coral restoration

Abstract It is essential to consider genetic composition for both conventional coral restoration management and for initiating new interventions to counter the significant global decline in living corals. Population genetic structure at a fine spatial scale should be carefully evaluated before implementing strategies to achieve self‐sustaining ecosystems via coral restoration. This study investigated the population genetic structure of two acroporid species at Kume Island, Okinawa, Japan. There were 140 colonies of Acropora digitifera collected from seven study sites, and 81 colonies of Acropora tenuis from six sites. In total, 384 single nucleotide polymorphism (SNP) loci for A. digitifera and 470 SNPs for A. tenuis were obtained using a comparatively economical technique, Multiplexed ISSR Genotyping by sequencing. Observed heterozygosity was significantly lower than expected heterozygosity at all SNP sites in both acroporid species, suggesting deficient genetic diversity possibly caused by past massive coral bleaching. Even though both species are broadcast spawners, the population structure was different in the two species. No detectable structure was evident in A. digitifera, but two distinct clades were found in A. tenuis. The genetic homogeneity of A. digitifera at Kume Island suggests that this species could be used as a focal species for active restoration in terms of genetic differentiation at this island. By contrast, A. tenuis unexpectedly included two distinct clades with little or no admixture within a small study area, possibly representing two reproductively isolated cryptic species. Thus, when using A. tenuis, it would be prudent to avoid disturbing the genetic composition of wild populations until this question is answered.

Shimajiri Group equivalent sedimentary rocks dredged from sea knolls off Kume Island, central Ryukyus: Implications for timing and mode of rifting of the middle Okinawa Trough back‐arc basin

AbstractThe late Cenozoic geohistory of the Ryukyu arc is closely related to the rifting history of the Okinawa Trough. The submarine geology and stratigraphy of areas around Kume Island, which is situated near the eastern rifted margin of the middle Okinawa Trough, provide key constraints to understand the timing and mode of Okinawa Trough rifting. Here we report the lithology of sedimentary rocks dredged along slopes of ~1000‐m‐deep sea knolls located north and northwest off Kume Island, and their depositional ages determined by calcareous nannofossils and strontium (Sr) isotope analyses. Various types of sedimentary rocks, such as siltstone, very fine‐grained sandstone, medium‐grained sandstone, fossiliferous coarse‐grained sandstone, and tuffaceous sandstone, were recovered at two dredge sites. These sedimentary rocks are lithologically similar to those in the Aka Formation and a part of the Maja Formation of the Shimajiri Group in nearby Kume Island. Calcareous nannofossils and Sr isotope analyses indicate their depositional ages from the early Pliocene to the early Pleistocene, which are generally consistent with those of the Aka Formation. The finding of the dredged rocks similar in lithology and ages to the Aka Formation indicates that marine deltaic area continued toward north and northwest from Kume Island during these periods. The presence of the Shimajiri Group equivalent sedimentary rocks at the dredge sites are likely related to the main rifting of the Okinawa Trough after ca. 2 Ma in the central Ryukyus.

Evaluation of geochemical records as a paleoenvironmental proxy in the hypercalcified demosponge Astrosclera willeyana

The geochemistry of the calcium carbonates of marine organisms is an excellent proxy for reconstruction of the paleoceanographic history. However, previous studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. Here, we investigated stable oxygen (δ18O) and carbon (δ13C) isotopes and minor and trace element (Mg, Sr, Ba, Pb, and U) to Ca ratios of 36 living sclerosponges (Astrosclera willeyana) collected from Kume Island in the Ryukyu Islands, southwestern Japan, to evaluate the utility of geochemistry as a paleoenvironmental proxy. The δ18O, δ13C, and Sr/Ca deviations of the coevally precipitated skeleton were extremely small and almost constant at all skeletal portions, strongly suggesting that within-skeletal variations in the chemical components are negligibly small for non-symbiotic sclerosponges. Mean δ18O, δ13C, and Sr/Ca values (N = 36), falling within a quite narrow range, showed no significant evidence for intraspecific (inter-specimen) variations in the sclerosponges. The sclerosponges δ18O and δ13C were consistent with those of the aragonites precipitated in isotopic equilibrium with seawater at the growth site. The sclerosponge Sr/Ca was close to that of inorganically precipitated aragonite, and the estimated partition coefficient of 1.1 (almost unity) is identical to previously reported values for different species (Ceratoporella nicholsoni). Consequently, these results suggest that A. willeyana sclerosponge, having little vital effects on the geochemistry, is a robust indicator of paleocean environments (seawater δ18O, temperature, and dissolved inorganic carbon δ13C). Further, our evaluation study documents that sclerosponges living in deeper ocean environments can support the reconstruction of spatial and vertical paleoceanographic changes in conjunction with coral proxy records. The sclerosponge U/Ca showed little within-skeletal and intraspecific variations, but the heterogeneity and individual difference of the Mg/Ca, Ba/Ca, and Pb/Ca were relatively large, the reasons of which still remain unresolved.

Detailed volcanic and tectonic morphology of Nakadomari Hill in the southern Okinawa Trough

Nakadomari Hill is an unexplored edifice in the southern Okinawa Trough back-arc basin where crustal extension by continental rifting occurs and few submarine eruptions associated with back-arc volcanism have been mapped in detail. High-resolution bathymetric mapping with an autonomous underwater vehicle (AUV) reveals that Nakadomari Hill is a submarine volcanic complex with recent lava flow eruptions. The high-resolution (2 m) bathymetry shows striking contrast between rugged terrain in the central area and the adjacent smooth terrain. The cone-shaped features in the rugged terrain are covered by ropey fabric with high acoustic reflectivity and are devoid of tectonic deformation, thus they are interpreted to be relatively younger lava domes. The cone-shaped features in the smooth terrain show low reflectivity and are dissected by ENE–WSW trending tectonic lineaments, suggesting they were formed during older volcanism. Nakadomari Hill developed through multi-stage eruptions before and after back-arc rifting and faulting. The ropey and curtain-folded morphology with high acoustic reflectivity are interpreted to be a field of lava flows and they are relatively young. The area considered to be lava flows is estimated to be over 13 km2, showing that eruptions in the southern Okinawa Trough have been extensive. An active volcanic system is supported by indicators of high-temperature hydrothermal venting. Hydrothermal plumes with concurrent sharp temperature increases of up to 0.17 °C were present even at the vehicle altitude of ~100 m above the bottom. The alignment of volcanic cone-shaped features at Nakadomari Hill is in the NNW–SSE direction which is clearly different from the orientation of local rifting (ENE–WSW). At a larger scale, the volcanic edifices west of Kume Island from the arc to back-arc are also aligned roughly in the NNW–SSE direction and they are sub-parallel to a major tectonic structure in the arc, the Kerama Gap. The agreement of the local volcanic and tectonic trends implies that magmatic focusing may have taken place along the tectonic structures of the Kerama gap and in turn caused the extensive back-arc volcanism in this area.

After the long summer: Death and survival of coral communities in the shallow waters of Kume Island, from the Ryukyu Archipelago

Coral reefs in the Ryukyu Islands, southern Japan, have been undergoing degradation for at least five decades. Recently, the archipelago has been hit by bleaching events for two consecutive years (summers of 2016–2017). Shallow coral communities have been reported as especially affected. In this study, using underwater transects, we assessed the status of shallow coral reef communities in Kume Island, at seven distinct locations in Shimajiri Bay, following reports from local fishermen and divers of heavy bleaching across the bay. Our data and analyses revealed that the benthic environment in the bay has algae as the main component, with an average coral cover of only 7.2%. Branching coral colonies, which used to be the most common morphology in Kume Island reefs, accounted for just 7.6% of the total coral cover. Notably, the genus Acropora was almost completely absent from our transects, although its recent presence was confirmed by dead colonies making up 4.12% of total transect coverage, suggesting that restoration efforts focused on this genus might be possible in the future. In order for these to be successful, however, a better understanding of the environmental situation at Kume Island is required, including the effects of human activities on coral reef communities.

Two large squat lobsters of the superfamily Chirostyloidea (Crustacea: Decapoda: Anomura) from the Ryukyu Islands, southwestern Japan, with description of a new species of the genus Eumunida Smith, 1883.

Two species of the chirostyloid families Sternostylidae and Eumunididae, Sternostylus investigatoris (Alcock Anderson, 1899) and Eumunida balteipes n. sp., are reported on the basis of material collected from deep waters off Kume Island, Ryukyu Islands, southwestern Japan. Sternostylus investigatoris is recorded for the first time and is the second species of the genus from Japanese waters. Eumunida balteipes n. sp. is morphologically closest to E. sternomaculata de Saint Laurent Macpherson, 1990, but the armature of the thoracic sternite 3 and P1 palm distinguishes the two species.

Long-term Monitoring of Metal Elements in Total Suspended Particle Aerosols Simultaneously Collected at Three Islands in Okinawa, Japan

In the present study, total suspended particle (TSP) aerosols were simultaneously collected using identical high-volume air samplers at three islands in Okinawa; Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS, Okinawa Island), from 2008 to 2012 Kume Island (KM, ca. 160 km south-west of CHAAMS), and Minami-Daitou Island (MD, ca. 320 km south-east of CHAAMS) from 2008 to 2010. The sample collected were analyzed using energy-dispersive X-ray fluorescence spectrometry (ED-XRF) and synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) to investigation long-range transport of metal elements to Okinawa from the Asian continent. From analytical data on samples collected at CHAAMS for five years, it was found that most elements (Ca, Fe, Ti, Mn, V, Cu, Ni, Pb, As, and Zn) in TSP aerosols showed higher concentrations in the period from October to May, when the continental air mass passed over Okinawa, regardless of Asian dust events. The annual average concentrations of Ni, Cu, Zn, As, Se, and Pb in TSP aerosol samples collected at three islands gradually decreased as the TSP aerosols traveled from west to east in any year. Based on the enrichment factors (EFs) and concentration ratios, it is considered that most of anthropogenic elements such as As, Pb, and Zn in TSP aerosols are derived from coal combustion in the Asian continent. Moreover, it is confirmed from the direction of the air mass reaching the sampling sites that Cu, Zn, As, and Pb in TSP aerosols were transported to the three islands in Okinawa by air mass not only from northwest and north, but also from the west. These TSP aerosols transported from the Asian continent may influences not only the atmospheric environment but also the concentrations of trace metals in coastal seawater in Okinawa, which have to be kept extremely low to preserve the diverse and unique ecosystem in coral reefs.

Preparation of standard materials of aerosol particles for X‐ray fluorescence analysis using a small chamber sampling unit

We investigated the simple and rapid preparation of standard materials of major and trace elements in aerosol particles for X‐ray fluorescence (XRF) analysis to study long‐range transport of air pollutants in East Asia. Standard materials for calibration curve were prepared using a small‐chamber sampling technique consisted of a 3‐L cylindrical acrylic chamber, aerosol filter holder, flow meter, and vacuum pump. Prepared aerosol standard materials had an excellent homogeneity in 0.5 mm × 0.5 mm analytical area. XRF analysis was performed by a bench top energy‐dispersive X‐ray fluorescent spectrometer. For only arsenic analysis, synchrotron radiation XRF was applied because As‐Kα line (10.53 keV) was overlapped by Pb‐Lα line (10.55 keV) in a typical XRF measurement. The calibration curves of 15 elements (K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, As, Se, Rb, Sr, Ba, and Pb) showed a good linearity. The prepared standard materials were applied to determine metal elements in total suspended particle (TSP) aerosols, which were collected at Kume Island in Okinawa, Japan, from June 2008 to June 2010, and analytical results in XRF were compared with those of inductively coupled plasma atomic mass spectrometry (ICP‐MS) or atomic absorption spectrometry (AAS). Analytical results of TSP aerosol between XRF and ICP‐MS or AAS had a strong correlation higher than 0.800 for all elements.

Reconstruction of the temporal distribution of 236U/238U in the Northwest Pacific Ocean using a coral core sample from the Kuroshio Current area

The temporal distribution of 236U in the Northwest Pacific Ocean was reconstructed through measurements of the annual changes in 236U/238U atom ratios in a coral core collected from Kume Island located within the Kuroshio Current region. In total, 74years (1940–2014) of temporal trend of 236U/238U atom ratios were reconstructed using Accelerator Mass Spectrometry (AMS). The annually resolved 236U/238U ratios showed a strong increase from 1952, and two prominent peaks were found in the annual bands for 1954 (11.0±1.2×10−9) and 1958 (8.55±1.17×10−9); also an enhanced peak was observed for the band of 1963 (3.51±0.20×10−9). These peaks coincided with the occurrence of large nuclear tests in the Pacific Proving Grounds and/or the highest global fallout rate, suggesting a clear influence of these nuclear events on 236U/238U atom ratios. Furthermore, the coral results showed some disagreement with the annual changes for 236U in East Asian corals collected at the entrance to the Sea of Japan. Based on these results, the mixing ratios of the surface seawater currents in the Northwest Pacific Ocean have been estimated.

Measurement on behavior of deep ocean water discharged in Maja Port in Kume Island

Measurement on behavior of deep ocean water discharged in Maja Port in Kume Island

Heat transfer characteristics of plate heat exchanger for desalination using deep seawater in Kume Island

Heat transfer characteristics of plate heat exchanger for desalination using deep seawater in Kume Island

Geomorphology of barrier reef in the eastern Kume Island based on multibeam bathymetry and SCUBA surveys

Geomorphology of barrier reef in the eastern Kume Island based on multibeam bathymetry and SCUBA surveys

Effects of Fipronil Bait on Sugarcane Growth and Yield on Kume Island, Okinawa, Japan

Effects of Fipronil Bait on Sugarcane Growth and Yield on Kume Island, Okinawa, Japan

A Study of Awareness of Local Residents on Tourism Promotion in Kume Island

A Study of Awareness of Local Residents on Tourism Promotion in Kume Island

Determinants of Farmers in Kume Island to Implement the Measures for Prevention of Red Clay Outflow and Crop Choice

Determinants of Farmers in Kume Island to Implement the Measures for Prevention of Red Clay Outflow and Crop Choice