Kerama Islands Research Articles

The genus Anacaena Thomson from the Ryukyu Archipelago of Japan (Coleoptera, Hydrophilidae)

We review the genus Anacaena Thomson, 1859 from the Ryukyu Archipelago, southern Japan. Three aquatic species are recognised: A. torikaiisp. nov. from Amami-ôshima Island, A. okinawanasp. nov. from Okinawa-jima Island and Kerama Islands, and A. kumejimanasp. nov. from Kumejima Island. All three species are very similar, with the morphology of the aedeagus being essential for a reliable identification. Dorsal colouration is also useful as a diagnostic character, despite some variation within species. We observe a possible geography-based variation between A. okinawana from Okinawa-jima I. and the neighbouring Kerama Is., but we treat both populations as conspecific based on genital morphology. Anacaena kumejimana and A. okinawana share many morphological characters possibly indicating their close relationship. We compare the endemism of aquatic Hydrophilidae in the Ryukyu Archipelago to that in other groups of aquatic beetles: the proportion of endemic species is higher in aquatic Hydrophilidae than in Dytiscidae, but much lower than in stream-inhabiting Hydraenidae and Elmidae. A list of Japanese species of Anacaena and a key to the Japanese species of the genus are provided.

Ascidians observed associating epizoically on holothurians in waters in the Kerama Islands, Okinawa, Japan

Photograph records of four holothurian individuals upon which colonial ascidians were associated epizoically are reported from the waters around Akajima Island, Kerama Islands, Okinawa, Japan. Although holothurians are known to be hosts of many organisms, these new observations add a new perspective to understanding the ecological role of holothurians as mobile scaffolds. Some ascidians have limited capabilities of locomotion, but we believe an association with holothurians would increase the mobility of ascidians. On the other hand, such associations may be beneficial as part of the holothurians’ chemical defenses, since some ascidians and/or harbored cyanobacteria produce bioactive compounds. Even though these observed cases may be temporary associations, it is apparent holothurians are ecosystem engineers on coral reefs not only due to their feeding behavior, but also due to their associated fauna.

Higher Genetic Diversity of the Common Sea Cucumber Holothuria (Halodeima) atra in Marine Protected Areas of the Central and Southern Ryukyu Islands

Recently, sea cucumbers (Echinodermata: Holothuroidea) have been over-exploited in many areas of the world, including in the Ryukyu Islands, southern Japan, due to increases in their economic importance. Nevertheless, management and protection of sea cucumbers are insufficient worldwide. The black sea cucumber Holothuria (Halodeima) atra Jaeger, 1833, inhabits a large range across the Indo-West Pacific Ocean and is a widely harvested species. Here we conducted population genetic analyses on H. atra using partial mitochondrial DNA sequences of cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S) to examine 11 different populations around three island groups in the middle Ryukyus; Okinawajima Island, the Kerama Islands, and the Sakishima Islands, all within Okinawa Prefecture. We found 27 haplotypes for COI and 16 haplotypes for 16S. Locations within national and quasi-national parks (Zamami Island, Keramas, and Manza, Okinawajima; managed by the national Ministry of Environment and Okinawa Prefecture, respectively) had the highest number of haplotypes, whereas locations with less management and more anthropogenic pressure had lower numbers The mean of all samples' genetic diversity indices was moderate with regards to both haplotype and nucleotide diversity. According to our results, Zamami Ama was the most genetically diverse location based on both markers used, likely because it is located within Kerama-Shoto National Park with comparatively stricter regulations than most other locations. Based on our COI sequences, three-quarters of the locations with the highest haplotype diversity were found to be distant from Okinawajima Island, indicating that the genetic diversity of H. atra was reduced around Okinawajima Island. Our results possibly reflect negative impacts from anthropogenic pressures such as over-harvesting and coastal development, although future comprehensive research including sequences of nuclear loci is needed to confirm this hypothesis.

Coupling high-resolution coral bleaching modeling with management practices to identify areas for conservation in a warming climate: Keramashoto National Park (Okinawa Prefecture, Japan)

Increases in sea-surface temperature due to global warming are a major threat to tropical and subtropical corals as exposure to high water temperatures is the primary cause of coral bleaching. To continue receiving high ecosystem services from coral reef ecosystems in the future, it is important to predict the growth conditions of corals and take appropriate countermeasures to protect them at both global and local scales. The Kerama Islands (part of the Nansei Islands, Japan) were selected as the study area. The islands have been designated as a national park and attract substantial tourism, which utilizes the coral reef ecosystem. The selected study site is significant as it is known to act as a source of coral larvae for the surrounding area. In this study, coral bleaching and mortality rates under present and +1.5 °C/+2.0 °C water temperature conditions were estimated using a 1) three-dimensional hydrodynamic model with a spatial resolution of 100 m and 2) statistical model describing the relationship between various environmental parameters and coral bleaching and mortality rates. Applying a local hydrodynamic model enabled us to obtain high-resolution spatial and temporal variations in water temperature and current speed, and these data were used to obtain statistical model data. Coral conservation sites were prioritized based on 1) projections of the spatial distribution of bleaching and mortality rates under global warming conditions and 2) locations of the main diving and conservation points, with the intention of continuing the present use and management locations. The results of this study are expected to contribute to the management of coral reef ecosystems through conservation and adaptation strategies at local scales.

Cocotropus aurantius, a new velvetfish (Aploactinidae) from Japan

The new velvetfish Cocotropus aurantius is described on the basis of a single specimen (17.1 mm standard length) collected off Nagannu Island, Kerama Islands, Japan, at a depth of ca. 50 m. An individual of the new species has also been photographed off Izu Peninsula, Japan. The species is characterized by XII, 8 dorsal-fin rays, II, 6 anal-fin rays, 13 pectoral-fin rays, 7 segmented lower caudal-fin rays, 26 vertebrae, an interneural space between the 7th and 8th vertebrae lacking dorsal-fin spine proximal pterygiophores, the 1st–4th dorsal-fin spines situated anterior to the 3rd neural spine, 5 preopercular spines, vomerine teeth absent, the 2nd mandibular pore on each side fused, and the head, body and fins somewhat orange when fresh (preserved condition creamy-white), and with numerous small scattered brownish blotches and streaks.

慶良間諸島渡嘉敷島渡嘉志久湾の魚類相:144 種の追加記録

慶良間諸島渡嘉敷島渡嘉志久湾の魚類相:144 種の追加記録

Distribution and Local Movement of Humpback Whales in Okinawan Waters Depend on Sex and Reproductive Status.

The distribution and local movement patterns of humpback whales in waters off the west coast of Okinawa Island, southwest Japan, were investigated using line transect and photo-identification methodologies. Line transect surveys were conducted from 2011 to 2014 and photo-identification survey from 2006 to 2012. During the surveys, humpback whales aggregated in the areas around Ie and Kerama Islands, and tended to travel along the inshore coast of Okinawa Island when they move locally between those two sites. A total of 496 humpback whales of the known sex were photo-identified (322 males, 75 females and 99 females with a calf). Of these, 24.8% were confirmed moving locally between the sites of Ie and Kerama Islands within the same season. Frequency rates of the local movement for males, females and females with a calf were 41.9, 25.0, and 15.1%, respectively; the frequency of local movement for males was significantly higher than that for females and females with a calf. These results indicate that male humpback whales tend to move more actively between the local breeding sites as compared to females and females with a calf. We speculate that the males search for more opportunities to mate, whereas females with a calf tend to remain in the same areas to nurse their calves. These findings extend our knowledge of the habitat use and reproductive ecology of humpback whales in Okinawan waters, which remain poorly understood.

Airborne Laser Bathymetry Technology

The Airborne Laser Bathymetry (ALB) is a technique to measure from an aircraft using a scanning (pulsed laser beams) and mainly used for hydrographic survey in shallow and moderately clear, nearshore coastal waters and lakes. Recently, ALB has been utilized for the verification of river surveying. It seems that it will become as a valuable sensor for rapid and accurate measurements in various fields in the near future. In this paper, in order to promote the usage of ALB in various fields, we have described the development history of ALB and measurement outline. We highlighted the differences from conventional airborne laser survey, and introduction of measurement examples in rivers (Yoshino River) and oceans (Kerama islands).

Spatial Distribution and Habitat Use Patterns of Humpback Whales in Okinawa, Japan

Abstract. Detailed knowledge of the population of humpback whales (Megaptera novaeangliae) in Okinawa is important for conservation management in this area; however, information on the spatial distribution of this population is limited. In this study, we investigated the distribution of whales using data on the sighting locations, water depth, and reproductive status of whales collected over 21 years in the area of Kerama and Ie Islands, Okinawa, Japan, one of the breeding grounds in the Western North Pacific. Of 1,402 whales that were photo-identified (856 males, 100 singers, 150 females, and 296 females with a calf), males, females, and singers were mainly distributed in deep offshore waters, while females with a calf were distributed in shallow interisland waters. The results suggest that certain reproductive activities, such as mating behavior or competition among males over females to mate, might occur in the offshore northern waters of Kerama Islands and western waters of Ie Island, while nurturing ...

Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan.

To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence‐based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.

Genome-wide SNP analysis explains coral diversity and recovery in the Ryukyu Archipelago.

Following a global coral bleaching event in 1998, Acropora corals surrounding most of Okinawa island (OI) were devastated, although they are now gradually recovering. In contrast, the Kerama Islands (KIs) only 30 km west of OI, have continuously hosted a great variety of healthy corals. Taking advantage of the decoded Acropora digitifera genome and using genome-wide SNP analyses, we clarified Acropora population structure in the southern Ryukyu Archipelago (sRA). Despite small genetic distances, we identified distinct clusters corresponding to specific island groups, suggesting infrequent long-distance dispersal within the sRA. Although the KIs were believed to supply coral larvae to OI, admixture analyses showed that such dispersal is much more limited than previously realized, indicating independent recovery of OI coral populations and the necessity of local conservation efforts for each region. We detected strong historical migration from the Yaeyama Islands (YIs) to OI, and suggest that the YIs are the original source of OI corals. In addition, migration edges to the KIs suggest that they are a historical sink population in the sRA, resulting in high diversity. This population genomics study provides the highest resolution data to date regarding coral population structure and history.

An individual-based model for population viability analysis of the brooding coral Seriatopora hystrix

Species of brooding corals are declining and disappeared from some reefs near southwestern Japan. We therefore developed an individual-based model of the threatened species Seriatopora hystrix to assess local population viability. Life history parameters of the individual colonies represented in the model were estimated from field observations made on a 5m×5m quadrat at Urunosachi, Kerama Islands, during 2009 and 2010. When assuming that recruitment was restricted to local self-recruitment, we found that the modelled Urunosachi population was maintained if the survival rate was equal to the upper limit of the 95% confidence interval, but gradually declined close to extinction after 10 years if the survival rate was the estimated means value. If larvae were supplied from outside the population, the population could persist over time even if the expected survival rate was considered, but the immigrating rate of larvae required for persistence was very high. Further research is necessary to locate other S. hystrix populations near the Urunosachi population and to evaluate the connectivity among populations to determine whether the Urunosachi population is viable. We also examined how many recruits from other populations were needed to initiate the recovery of the population if it was severely affected by certain disturbances. Constant recruitment or occasional high-level recruitment could promote the recovery of the S. hystrix population.

特集「シカの採食圧による植生被害防除と回復」 1983～1984 年時点での慶良間群島阿嘉島におけるケラマジカの樹皮剥皮

1983～1984 年に慶良間群島阿嘉島（4.00 km2)において，メッシュ法（100 m×100 m)を用い，樹木およびケラマジカ（Cervus nippon var. keramae Kuroda)による樹皮剥皮の島内分布を調査した。全400 メッシュのうち95 メッシュ（23.8％)で樹皮の剥皮が認められた。全調査を通じて，108 種の樹木を記録し，そのうち22 種（高木16 種，小高木6 種)で剥皮が認められた。剥皮が認められたメッシュ割合が最も高かったモチノキにおいても，その値は約3 割に過ぎず剥皮を受けていない立木が多く存在していた。

Extended geographic distribution of several Indo-Pacific coral reef diseases

Other than coral bleaching, few coral diseases or diseases of other reef organisms have been reported from Japan. This is the first report of lesions similar to Porites ulcerative white spots (PUWS), brown band disease (BrB), pigmentation response (PR), and crustose coralline white syndrome (CCWS) for this region. To assess the health status and disease prevalence, qualitative and quantitative surveys (3 belt transects of 100 m² each on each reef) were performed in March and September 2010 on 2 reefs of the Ginowan-Ooyama reef complex off Okinawa, and 2 protected reefs off Zamani Island, in the Kerama Islands 40 km west of Okinawa. Overall, mean (±SD) disease prevalence was higher in Ginowan-Ooyama (9.7 ± 7.9%) compared to Zamami (3.6 ± 4.6%). Porites lutea was most affected by PUWS at Ooyama (23.1 ± 10.4 vs. 4.5 ± 5.2%). White syndrome (WS) mostly affected Acropora cytherea (12. 5 ± 18.0%) in Zamami and Oxipora lacera (10.2 ± 10%) in Ooyama. Growth anomalies (GA) and BrB were only observed on A. cytherea (8.3 ± 6.2%) and A. nobilis (0.8%) at Zamami. Black band disease affected Pachyseris speciosa (6.0 ± 4.6%) in Ooyama only. Pigmentation responses (PR) were common in massive Porites in both localities (2.6 ± 1.9 and 5.6 ± 2.3% respectively). Crustose coralline white syndrome (CCWS) was observed in both localities. These results significantly expand the geographic distribution of PUWS, BrB, PR and CCWS in the Indo-Pacific, indicating that the northernmost coral reefs in the western Pacific are susceptible to a larger number of coral diseases than previously thought.

A new anthiine fish, Anthias truncatus, from the Kerama Islands, Okinawa

A new anthiine fish, Anthias truncatus, from the Kerama Islands, Okinawa

Degree and Pattern of Gene Flow in Several Scleractinian Corals in the Ryukyu Archipelago, Southern Japan1

Dispersal distance of planktonic larvae of coral reef organisms is influenced by their ecological characteristics and environmental factors such as current flow and physical structure of reefs. This study reviews the degree and pattern of genetic differentiation in scleractinian corals in the Ryukyu Archipelago, compared with other regions. Small-scale genetic heterogeneity, but broad-scale homogeneity, was detected in some species, including brooders and spawners in the Ryukyus. Comparison with other regions indicated that limited gene flow on a small spatial scale (i.e., self-recruitment) seemed to occur in many regions. However, the degree of gene flow over larger distances was complex and species-dependent. With an implication for conservation in the Ryukyus, the larval source hypothesis, which states that coral larvae were recruited from the Kerama Islands to the Okinawa Islands, was consistent with results illustrating high gene flow in some species. Thus, conservation of corals in the Kerama Islands is high priority. Detection of genetic breaks between the southern and central Ryukyus was not common among species. The genetic structure observed in corals is highly variable and depends on both species and spatial scale in the Ryukyus. In addition, the complex genetic structures of corals may be related to coral-specific destructive events, such as bleaching, outbreaks of crown-of-thorns starfish, and disease. Further studies will provide new insights and a more detailed view of the genetic structure of corals by using different markers (e.g., microsatellites) and approaches (assignment tests and clustering analysis), which will provide useful information for coral reef conservation.

Phylogenetic Analysis of Carotenoid-Producing Marine Microorganisms Around the Coral Reefs of the Kerama Islands of Okinawa

Seawater sample from the coral reefs of the Kerama Islands of Okinawa were assessed for the presence of carotenoid-producing bacteria. Results of 16S rDNA analysis of the bacteria obtained from the isolated bacteria showed unique patterns that were different from those of the bacteria obtained from the ordinary marine area. Phylogenetic analysis revealed a slight correlation with the statistical analysis of the PDA chart patterns. The results suggest that useful materials for human health such as carotenoids can be extracted from many carotenoid-producing bacteria such as those found the coral reefs the Kerama Islands.

琉球列島四万十帯中の現地性緑色岩の産状と化学組成

This paper concerns the occurrence and chemical compositions of “in-situ” greenstones in the Nago and Kerama Formations in the Okinawa and Kerama Islands, which belong to the Shimanto Belt of Cretaceous-Paleogene age. The in-situ greenstones are composed of metabasaltic pillow lava, pillow breccia, hyaloclastite and sills. These are closely interbedded with, or grade upward into, pelitic rock (in Nago Fm.) and sandstone (in Kerama Fm.), indicative of a volcanism near trench. The greenstones have geochemical features of N-MORB in terms of high-field strength element (HFSE) and rare-earth element (REE) chemistry. The relict Cr-spinel composition also support this bulk chemical characteristics. They may have been produced at the spreading ridge between the Kula and Pacific plates, which is thought to have passed northward along the SW Japan arc through Cretaceous and Paleogene. Assuming a ridge migration rate of 4 cm/year, we infer that ages of the Nago and Kerama Formations are about 95-100 Ma.

Cocotropus keramaensis , a new species of the family Aploactinidae (Teleostei) from the Kerama Islands, southern Japan

A new species of aploactinid, Cocotropus keramaensis, is described based on a single specimen collected off the Kerama Islands, southern Japan. This new species is separable from other known congeners in the following combination of characters: XII, 10 dorsal fin rays; II, 7 anal fin rays; 13 pectoral fin rays; 26 vertebrae; 4 + 8 = 12 gill rakers; five distinct preopercular spines; upper jaw longer than the lachrymal; single papilla on the posterior portion of the maxilla; outer edge of the lower jaw with four distinct papillae; first sensory pore of the lower jaw on both sides fused; anterior tip of the isthmus reaching to the fifth sensory pore of the lower jaw; and anterior four dorsal spines anterior to the third neural spine.

Protest Responses in Contingent Valuation Method for Coral Reefs in Kerama Islands

The purpose of this paper is to estimate the value of the coral reefs in the Kerama Islands in Okinawa and to clarify the reasons for biases in the responses to the questionnaires. This research was conducted at Zamami village in March 2003, and the respondents to the questionnaires were passengers on ships between Naha and Zamami. The questionnaire is based on “Contingent Valuation Method” (CVM), which is used to evaluate the non-used value of the environment. In this questionnaire, we used the “double-bounded two-choice approach” in order to determine the passengers' willingness to pay (WTP) for the conservation of Kerama's coral reefs.Coral reefs are very important resources for ecology and the economy, especially in island areas like Okinawa. They have several public functions that provide material and spiritual benefits to human beings with regard to fisheries, ocean biodiversity value, purification of the ocean, underwater views, coastal protection, resources for tourism and recreation and so on. Recently, however, the drastic changes in certain environmental conditions have caused considerable damage to the coral reefs. We should recognize the necessity of protecting the coral reefs in order to retain their public functions; hence, we attempted to define the value of conservation of the Kerama coral reefs.First, we estimated the passengers' WTP for the conservation of the Kerama coral reefs, using the Turnbull method, which is a type of survival analysis. The results revealed that the average WTP per person was 3, 995 yen, and the total value for the annual passengers traveling to Zamami village was 367, 488, 065 yen per year.Second, we considered protest responses in order to assess the reliability of CVM as a method of evaluating environmental value. A total of 94 protest responses were obtained in this research, and we analyzed the reasons for which the respondents expressed objections to the scenario presented in this questionnaire. We clarified four factors: The method of payment, the taxable, the area of conservation, and the misunderstanding of the scenario presented. Closely performing a pre-test can solve some of these problems.While CVM is one of the small-number methods that can measure the non-used value of the environment, such as biodiversity conservation, its results are debatable due to its hypothetical character. Therefore, we will continue to examine the reliability of CVM by repeating this research.