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Global warming causes functional shifts and reorganisation in marine communities through range shifts to high-latitude reefs and cnidarian bleaching mortality in the tropics. Such changes threaten the integrity and structure of marine communities, especially as foundational and associated species are reduced or lost. However, comparatively little is known about the extent of range shifts and their ecological consequences for the overlooked components of marine ecosystems, such as octocorals and zoantharians (O + Z) on shallow coral reefs. As these groups play a crucial part in building complexity and sustaining life in reef communities, functional shifts in these taxa may cascade through the entire ecosystem, but these processes have not been quantified. Here, we examined the environmental drivers and functional consequences of spatial variation in octocoral and zoantharian communities across 27 sites in southern Japan, spanning from tropical to warm-temperate waters. We collated a trait database for 42 entities (species, genus, and family level identifications) of octocorals and zoantharians and calculated functional diversity and functional richness to measure functional compositional change. We identified five functional groups according to their trait similarities and identified how their abundances respond to changing environmental factors with general additive models (GAMs). We found functional shifts among octocorals and zoantharians across the tropical to temperate thermal gradient, with the abundances of two functional groups best explained by gradients in minimum sea surface temperature. Non-linear relationships between the functional groups and thermal gradients imply a more intricate relationship than expected, suggesting other non-temperature-based drivers, e.g., nitrogen or pH levels might also play an important role. Only functional group richness and species richness showed significant correlations with latitude, whilst functional diversity and functional richness did not. Our results indicate that octocoral and zoantharian communities and functionality potentially undergo shifts with clear community compositional changes, influenced by climate change across environmental gradients. However, the taxonomy and identification of these taxa remain difficult, and information on functional traits is often sparse or not species-specific, indicating a clear need for further basic zoological and ecological work on octocorals and zoantharians. [ABSTRACT FROM AUTHOR]

Aims: Transformation of species and functional composition on subtropical reefs are ongoing due to poleward range shifts of some tropical species, with largely unknown consequences to ecosystem functioning. Trait‐based approaches are powerful tools to quantify such changes. Here, we evaluated changes in the trait composition of coral‐associated fish assemblages along a tropical‐to‐temperate environmental gradient of ca. 1400 km in southern Japan with abundance‐weighted trait expression to assess how trait composition changes with increasing latitude. Location: Ryukyu Islands and southern Pacific coast of Japan. Taxon: Reef fish. Methods: We tested for shifts in trait space and functional redundancy, based on five morphological, life history and behavioural traits: maximum length, pelagic larval duration, trophic level, substrate preference and reproductive mode. Our trait database was coded with two approaches, first, by attributing a single value to each trait per species, and second, by fuzzy coding that allows more than one value per trait and hence considers some intraspecific trait variation. Results: We found a reduction in specialist habitat traits (coral substrate preference, nesters and herbivores) and an increase in generalist traits (predators) with increasing latitude, along with a contraction in trait space from tropical‐to‐temperate reefs. Functional redundancy declined with increasing latitude. These trends were closely linked with latitudinal gradients in temperature, along with changes in other environmental factors such as turbidity and photosynthetically active radiation. Main Conclusion: Functional turnover and contractions are thus likely due to the marginal conditions for coral‐associated fishes at higher latitudes, favouring generalist species, whereas increased resources at lower latitudes favour high redundancy and niche partitioning. Accounting for intraspecific trait variation indicated the same trends but highlighted increased functional vulnerability across all sites. We show that trait complexity in coral‐associated fish communities decreases from tropical‐to‐temperate reefs, highlighting the reduced functional scope that comes with marginal environmental conditions. [ABSTRACT FROM AUTHOR]

The soft coral order Alcyonacea is a common coral found in the deep sea and plays a crucial role in the deep-sea ecosystem. This study aims to predict the distribution of Alcyonacea in the western Pacific Ocean using four machine learning-based species distribution models. The performance of these models is also evaluated. The results indicate a high consistency among the prediction results of the different models. The soft coral order is primarily distributed in the Thousand Islands Basin, Japan Trench, and Thousand Islands Trench. Water depth and silicate content are identified as important environmental factors influencing the distribution of Alcyonacea. The RF, Maxent, and XGBoost models demonstrate high accuracies, with the RF model exhibiting the highest prediction accuracy. However, the Maxent model outperforms the other three models in data processing. Developing a high-resolution, high-accuracy, and high-precision habitat suitability model for soft corals can provide a scientific basis and reference for China's exploration and research in the deep sea field and aid in the planning of protected areas in the high seas. [ABSTRACT FROM AUTHOR]

The persistent exposure of coral assemblages to more variable abiotic regimes is assumed to augment their resilience to future climatic variability. Yet, while the determinants of coral population resilience across species remain unknown, we are unable to predict the winners and losers across reef ecosystems exposed to increasingly variable conditions. Using annual surveys of 3171 coral individuals across Australia and Japan (2016–2019), we explore spatial variation across the short‐ and long‐term dynamics of competitive, stress‐tolerant, and weedy assemblages to evaluate how abiotic variability mediates the structural composition of coral assemblages. We illustrate how, by promoting short‐term potential over long‐term performance, coral assemblages can reduce their vulnerability to stochastic environments. However, compared to stress‐tolerant, and weedy assemblages, competitive coral taxa display a reduced capacity for elevating their short‐term potential. Accordingly, future climatic shifts threaten the structural complexity of coral assemblages in variable environments, emulating the degradation expected across global tropical reefs. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems are highly sensitive to climate change. The Amami Islands in Southern Japan were selected as the study area. It is important to select areas that should be given priority for conservation and subsequently direct resources there. The objective of this study was to identify locations with low bleaching potential against future increases in water temperature, as well as high larval recruitment from other areas and high larval supply capacity to other areas based on connectivity. We simulated the coral bleaching rate and larval connectivity under historical (2000s) and future (RCP2.6 and RCP8.5 in the 2090s) climate conditions using a high-resolution (1/30° × 1/50°) future ocean regional projection dataset. From the model simulation, coral bleaching did not occur in most areas in the 2000s. However, the bleaching frequency would increase significantly under RCP8.5 in the 2090s, and it is projected that mass coral bleaching events will occur in more than half of the years of that decade. Larval dispersion simulation shows that some particles released from the Amami Islands remain in the same area. However, fluctuations in both the sink strength and the source strength among the islands were larger than those within each island, and differences in connectivity between scenarios were not apparent. Grid cells that have a low bleaching rate and high potential for a larval sink and source under each scenario were selected. Since our results can identify priority conservation areas, it is important to conduct conservation and/or adaptation strategies according to the specific characteristics of each island. [ABSTRACT FROM AUTHOR]

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. • We coupled sediment runoff model, hydrodynamic model and sediment dispersal model. • We simulated spatio-temporal variations in water temperature and terrestrial load. • We estimated priority sites for coral aquaculture in a small bay in southern Japan. [ABSTRACT FROM AUTHOR]

Devastating bleaching of coral communities at Amitori Bay, Iriomote Island, Japan, occurred in 2016 during the third global mass bleaching event in 2014–2017. The present study documented changes in coral communities in Amitori Bay from just before until after the 2016 bleaching event (2016–2020), by measuring coral cover and recruitment at nine sites (with two additional sites in 2018) in the bay. Spawning rates of acroporid corals were also monitored from 2017 to 2019 by visual observation and using bundle collectors to observe how long the effect of bleaching persisted. Reductions of 64.7 and 89.5% from 2016 to 2017 were observed in cover and recruitment of all coral families, respectively. Coral cover of all coral families recovered to pre-bleaching levels by 2020 and recruitment in 2020 was about two times greater than the pre-bleaching level. These results mirrored those of acroporids. Spawning rates of Acropora corals increased significantly from 40.6% in 2017 to 90.0% in 2019. Recovery of coral cover 4 years after the severe bleaching event was likely related to regrowth of remnants and of surviving juveniles of < 5 cm. The sudden increase in recruitment was likely driven by a combination of larval supply from other populations, increased numbers of reproductive adults, increases in spawning rates, and increased larval retention in the bay due to wind conditions in 2020. This study suggests that coral communities as in Amitori Bay will be critical for local-scale community persistence, serving as both source and sink populations. [ABSTRACT FROM AUTHOR]

We report the presence of the coral-killing sponge species Chalinula nematifera (de Laubenfels, 1954) in southern Japan via photographic records and specimens. The species appears to be a substrate generalist on scleractinians and occasionally octocorals, and is found across a wide variety of depths (0 to 24 m), as has been recently reported for this species from Indonesia. From our information, the species is found in southern Japan across the southern and central Ryukyu Islands, with a northern limit of Amami-Oshima Island, although future work will likely expand the range. As our records stretch back more than 20 years, we do not believe Chalinula nematifera is a recent arrival to the region. Due to the potential for this species to harm coral reefs, we suggest field surveys are needed to establish a baseline distribution and abundance database to aid in future monitoring. [ABSTRACT FROM AUTHOR]

Underwater image segmentation is useful for benthic habitat mapping and monitoring; however, manual annotation is time-consuming and tedious. We propose automated segmentation of benthic habitats using unsupervised semantic algorithms. Four such algorithms––Fast and Robust Fuzzy C-Means (FR), Superpixel-Based Fast Fuzzy C-Means (FF), Otsu clustering (OS), and K-means segmentation (KM)––were tested for accuracy for segmentation. Further, YCbCr and the Commission Internationale de l'Éclairage (CIE) LAB color spaces were evaluated to correct variations in image illumination and shadow effects. Benthic habitat field data from a geo-located high-resolution towed camera were used to evaluate proposed algorithms. The Shiraho study area, located off Ishigaki Island, Japan, was used, and six benthic habitats were classified. These categories were corals (Acropora and Porites), blue corals (Heliopora coerulea), brown algae, other algae, sediments, and seagrass (Thalassia hemprichii). Analysis showed that the K-means clustering algorithm yielded the highest overall accuracy. However, the differences between the KM and OS overall accuracies were statistically insignificant at the 5% level. Findings showed the importance of eliminating underwater illumination variations and outperformance of the red difference chrominance values (Cr) in the YCbCr color space for habitat segmentation. The proposed framework enhanced the automation of benthic habitat classification processes. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the controlling factor/s of coral growth in the northwest Pacific during the Holocene. Here, we present newly acquired growth data and radiocarbon age dates of fossil Porites corals collected from Holocene uplifted marine terraces in Kikaijima, southern Japan and northwest Luzon, Philippines. Carbonate mineral identification using X-ray diffraction (XRD) and scanning electron microscope (SEM) was conducted to screen for any diagenetic alteration in the fossil corals. We used accelerator mass spectrometer (AMS) - 14C dating to determine the absolute age dates of the fossil corals. Well-preserved fossil corals yielded radiocarbon age dates of 3235 ± 20 and 5712 ± 24 cal. yr BP for Kikaijima and 6285 ± 79, 6144 ± 77, 4336 ± 21, 4277 ± 19, 4200 ± 20, and 2972 ± 70 cal. yr BP for northwest Luzon. X-ray imaging of a 5-mm thick coral slab was utilized to measure growth variables. Linear extension rate, skeletal density, and calcification rate of Kikaijima corals are 3.77-8.72 mm/yr, 1.71-1.87 g/cm3, and 0.70-1.56 g/cm2yr, respectively. Linear extension rate, skeletal density, and calcification rate from northwest Luzon corals are 10.17-17.6 mm/yr, 0.66-1.67 g/cm3, and 0.91-2.81 g/cm2yr, respectively. Average linear extension rate from both sites was significantly and positively related to average calcification rate (r = 0.72, p = 0.019, n = 10). Skeletal density and linear extension rate measured from both sites were inversely related with each other (r = -0.56, p = 0.09, n = 10). Our data suggest that the variations in linear extension rates of fossil corals were influenced by the sea surface temperature (SST) difference between the study sites. However, data from modern corals are still needed to establish the local linear extension rate-SST relationship and to quantitatively evaluate how coral growth changes with respect to SST. Geomorphological, sedimentological, and geochronological studies of Holocene uplifted marine terraces should be conducted to provide the timing of emergence and coral reef development during Holocene. [ABSTRACT FROM AUTHOR]

Anthropogenic emission ofCO2 into the atmosphere has been increasing exponentially, causing ocean acidification (OA) and ocean warming (OW). The "business-as-usual" scenario predicts that the atmospheric concentration of CO2 may exceed 1,000 matm and seawater temperature may increase by up to 3 °C by the end of the 21st century. Increases in OA and OW may negatively affect the growth and survival of reef corals. In the present study, we separately examined the effects of OW and OA on the corals Acropora digitifera and Montipora digitata, which are dominant coral species occurring along the Ryukyu Archipelago, Japan, at three temperatures (28 °C, 30 °C, and 32 °C) and following four pCO2 treatments (400, 600, 800, and 1,000 matm) in aquarium experiments. In the OW experiment, the calcification rate (pD0:02), endosymbiont density, and maximum photosynthetic efficiency (Fv/Fm) (both p<0:0001) decreased significantly at the highest temperature (32 °C) compared to those at the lower temperatures (28 °C and 30 °C) in both species. In the OA experiment, the calcification rate decreased significantly as pCO2 increased (p < 0:0001), whereas endosymbiont density, chlorophyll content, and Fv/Fm were not affected. The calcification rate of A. digitifera showed greater decreases from 30 °C to 32 °C than that of M. digitata. The calcification of the two species responded differently to OW and OA. These results suggest that A. digitifera is more sensitive to OW than M. digitata, whereas M. digitata is more sensitive to OA. Thus, differences in the sensitivity of the two coral species to OW and OA might be attributed to differences in the endosymbiont species and high calcification rates, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the species occurrence record of zooxanthellate reef‐building corals at 1047 sites on the Japanese coast, recorded from 1929 to 2017. The dataset includes 484 confirmed scientific species names compiled from 152 literature sources, most of which were written in Japanese and published as gray literature in local journals or individual reports. Scientific names were consolidated under currently accepted nomenclature based on the World Register of Marine Species. Further revision of species names was made by referring to monographs on temperate coral species of Japan, along with expert knowledge. The dataset includes the coral species recorded each year at each study site, the geographical location of each site, and the scientific names of the corals. Three supporting datasets were created, containing a list of literature, the names of the sites and synonymization and confirmation of the coral names. This up‐to‐date collection of data is a contribution to the study of coral biogeography and conservation planning, as well as long‐term changes in coral species distributions in response to climate change. The complete data set for this abstract published in the Data Paper section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2020-08.1/jalter-en. [ABSTRACT FROM AUTHOR]

Climate change is projected to have large impacts on natural capital and ecosystem services under scenarios of the IPCC. In the summer of 2016, elevated seawater temperatures triggered mass coral bleaching in Sekisei Lagoon, southern Japan. Based on data from field surveys and relevant websites, we mapped potential stocks of four major ecosystem services (fisheries production, aquarium fish production, recreational diving, and seaweed control) supplied by coral reef fishes before and after the bleaching event and predicted the possible future state of socio-ecological systems in the lagoon under climate change. We also evaluated whether current management options had mitigated the negative effects of extreme heating and coral bleaching on the potential stocks. Before the coral bleaching, the potential stock of recreational diving was estimated as 41.44 billion Japanese yen per year for the entire lagoon, while those of fisheries and aquarium fish productions were 2.10 billion and 15.03 billion yen, respectively. After bleaching, the four potential stocks including seaweed control decreased. The marine park zone and the extermination area of crown of thorns starfish mitigated changes in fish species richness and the value of recreational diving following coral bleaching. Extreme heating and coral bleaching are considered to be representative of a possible future state under global warming, and the results suggest that even management for local disturbances can mitigate the interactive effect of climate change on the potential stocks. Additional integrative management accounting for climate change and local stressors would be necessary for protecting ecosystem services in Sekisei Lagoon. [ABSTRACT FROM AUTHOR]

Artificial barriers for coastal protection have been deployed across numerous tropical and subtropical islands in the Pacific, including Okinawa Island, southern Japan, where artificial defences have been installed along a large part of the coastline.Although artificial barriers can lead to beach narrowing or loss and can exacerbate erosion, their effects on coral reef ecosystems remain understudied.This study investigated the impact of a tetrapod breakwater in Ogimi Village, Okinawa Island, Japan, comparing the area affected by the presence of the barrier with a nearby natural coastline, and examining differences in physical parameters (depth profiles, sediment granulometry, and erosion on plaster balls) and benthic community composition.Significant differences in depth profiles, sediment granulometry, and erosion were found, suggestive of alterations in water energy levels (lower than controls on the landward side of the barrier, and higher on the seaward side).The benthic community was also clearly affected, with almost no living corals growing over the blocks or in their proximity.Overall, the data show how breakwaters can affect the physical environment and benthic communities in a subtropical coral reef ecosystem, with negative consequences for coral survival. [ABSTRACT FROM AUTHOR]

In 2016, global temperatures were the highest on record, and mass coral bleaching occurred world-wide. However, around Sesoko Island, Okinawa, southwestern Japan, the heat stress assessed by degree heating week (DHW) based on local temperature measurements was moderate in 2016; in 1998, DHW was three times higher than in 2016 (10.6 vs. 3.3 in September in respective years). On a reef flat of Sesoko Island where the effect of severe coral bleaching on coral assemblage was monitored in 1998, significant coral bleaching occurred in 2016. Bleaching of the heat stress sensitive Acropora corals began in July 2016 on the reef flat as seawater temperature rose. We observed the bleaching and post-bleaching mortality status of individual colonies of Acropora spp. in 2016 in fixed plots on the reef flat. In total, 123 Acropora colonies were followed for six months after seawater temperature became normal by multiple surveys. At the beginning of September 2016, 99.2% of colonies, were either completely (92.7%) or partially (6.5%) bleached. Of those, the dominant species or species groups were A. gemmifera (Ag), A. digitifera (Ad), and tabular Acropora (tA). For all Acropora colonies, the overall whole and partial mortality was 41.5% and 11.4%, respectively. Whole mortality rate differed significantly among species; 72.5%, 17.9%, and 27.8% in Ag, Ad, and tA, respectively. Mortality rates at the end of the surveys were similar in smaller (≤10 cm in diameter) and larger Ag, but the former suffered mortality earlier than the latter. Higher survival of smaller colonies was observed only in tA (100%), which may be associated with large morphological differences between smaller and larger colonies. Some of the dominant Acropora colonies had survived without partial mortality including 15.0% survival of the most vulnerable Ag at the end of the surveys. These results suggest that moderate heat stress may have a potential for selecting heat-tolerant genotypes. A longer period of mortality lasting for six months, was observed in Ag in addition to immediate whole mortality after bleaching, due to the continuous loss of living tissue by partial mortality. This highlights the need for multiple surveys at least during several months to accurately assess the impact of thermal stress event to corals. In contrast to DHW based on local measurements, DHW obtained from satellite data were similar between 1998 and 2016. Although satellite-based measurement of sea surface temperature is very useful to reveal variations in heat stress at a large spatial scale, temperature should be measured on site when variations at smaller spatial scales are of interest. [ABSTRACT FROM AUTHOR]

While widely known for their destructive power, typhoon events can also bring benefit to coral reef ecosystems through typhoon-induced cooling which can mitigate against thermally stressful conditions causing coral bleaching. Sensor deployments in Sekisei Lagoon, Japan's largest coral reef area, during the summer months of 2013, 2014, and 2015 were able to capture local hydrodynamic features of numerous typhoon passages. In particular, typhoons 2015-13 and 2015-15 featured steep drops in near-bottom temperature of 5 °C or more in the north and south sides of Sekisei Lagoon, respectively, indicating local cooling patterns which appeared to depend on the track and intensity of the passing typhoon. This was further investigated using Regional Ocean Modeling System (ROMS) numerical simulations conducted for the summer of 2015. The modeling results showed a cooling trend to the north of the Yaeyama Islands during the passage of typhoon 2015-13, and a cooling trend that moved clockwise from north to south of the islands during the passage of typhoon 2015-15. These local cooling events may have been initiated by the Yaeyama Islands acting as an obstacle to a strong typhoon-generated flow which was modulated and led to prominent cooling of waters on the leeward sides. These lower temperature waters from offshore may then be transported to the shallower inner parts of the lagoon area, which may partly be due to density-driven currents generated by the offshore-inner area temperature difference. [ABSTRACT FROM AUTHOR]

In the innermost region of the Ariake Sea, Japan, the diatom Asteroplanus karianus (Grunow) C. Gardner & R.M. Crawford frequently forms massive blooms in winter, causing bleaching of cultured nori (Neopyropia) by exhausting seawater nutrients. To understand the bloom-forming mechanism of A. karianus , the effects of temperature and salinity on the rejuvenation of resting cells and the growth of rejuvenated vegetative cells were examined in the laboratory. Surface sediments from the Ariake Sea were cultured at 6.5, 10, 15, 20, 25, 27.5, and 30°C in media with a salinity of 30 to determine the suitable temperatures for rejuvenation and subsequent growth. A suitable temperature range for the rejuvenation and subsequent growth of A. karianus was found to be 10–20°C, and 15°C was revealed to be the optimum temperature. The sediments were then cultured in media with salinities of 3, 7.5, 12, 16.5, 21, 25.5, and 30 at 15°C to determine suitable salinity for rejuvenation and subsequent growth. The suitable salinity range for the rejuvenation was found to be 16.5–30, and growth of the rejuvenated vegetative cells at salinities of 25.5 and 30 was higher than at 16.5 and 21. These results suggest that suitable temperatures and salinities for the rejuvenation and subsequent growth of rejuvenated vegetative cells were 10–20°C and 25.5–30, respectively. This study suggested that A. karianus can bloom only in winter because the low water temperatures in late autumn and winter allowed for active rejuvenation and subsequent growth of A. karianus. • Suitable conditions for Asteroplanus karianus rejuvenation and growth were studied. • Temperatures of 10–20°C and salinities of 25.5–30 promoted rejuvenation and growth. • Optimum temperature for rejuvenation and subsequent growth was 15°C. • Active rejuvenation and subsequent growth at low temperatures lead to winter blooms. [ABSTRACT FROM AUTHOR]

Coastal ecosystems consisting of coral communities have high ecosystem services and are important for tourism, fisheries, and the maintenance of biodiversity. Corals are often considered a major tourist resource in national parks located in the southern part of Japan. However, due to global-scale stresses such as climate change and local-scale stresses such as mass outbreaks of coral predators, there is a need to consider appropriate management and countermeasures. Two national parks in the subtropical zone (Keramashoto and Amamigunto national parks) and one national park in the temperate zone (Ashizuri-Uwakai National Park) in Japan were selected as a case study. The objectives of this study were to determine the status of coral conservation/management from websites and reports, and to clarify perceptions/concerns about climate change impacts through interviews with local stakeholders. The overall aim was to identify challenges in achieving sustainable use of coral ecosystems in national parks under climate change. In all of the national parks, the use of the sea area for tourism, such as diving, was very active. At the same time, coral monitoring and culling of predators were being carried out. However, the results of the interviews revealed that each park had different issues in implementing conservation activities, and Ashizuri-Uwakai showed a lack of manpower compared to the other two parks due to the scattered distribution of diving operators. From the interviews on the impacts of climate change, the increases in air and water temperatures were recognized in all parks and were consistent with the actual observed data. In terms of future concerns, increased coral bleaching frequency was common. Text mining showed that perceptions of coastal resources differed among parks and between occupations (tourism, fisheries, and government). Since concerns about climate change varied among regions and conservation activity systems also differed, it is important to consider and implement adaptation measures based on an appropriate understanding of local conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Coral bleaching, triggered by elevated sea-surface temperatures (SSTs) has caused a decline in coral cover and changes in the abundances of corals on reefs worldwide. Coral decline can be exacerbated by the effects of local stressors like turbidity, yet some reefs with a natural history of turbidity can support healthy and resilient coral communities. However, little is known about responses of coral communities to bleaching events on anthropogenically turbid reefs as a result of recent (post World War II) terrestrial runoff. Analysis of region-scale coral cover and species abundance at 17–20 sites on the turbid reefs of Okinawa Island (total of 79 species, 30 genera, and 13 families) from 1995 to 2009 indicates that coral cover decreased drastically, from 24.4% to 7.5% (1.1%/year), subsequent to bleaching events in 1998 and 2001. This dramatic decrease in coral cover corresponded to the demise of Acropora species (e.g., A. digitifera) by 2009, when Acropora had mostly disappeared from turbid reefs on Okinawa Island. In contrast, Merulinidae species (e.g., Dipsastraea pallida/speciosa/favus) and Porites species (e.g., P. lutea/australiensis), which are characterized by tolerance to thermal stress, survived on turbid reefs of Okinawa Island throughout the period. Our results suggest that high turbidity, influenced by recent terrestrial runoff, could have caused a reduction in resilience of Acropora species to severe thermal stress events, because the corals could not have adapted to a relatively recent decline in water quality. The coral reef ecosystems of Okinawa Island will be severely impoverished if Acropora species fail to recover. [ABSTRACT FROM AUTHOR]

Knowledge of genetic connectivity is useful for understanding of the recovery potential of coral populations after various disturbances, such as coral mass bleaching. Population genetic studies in corals are mostly restricted to Australian and Caribbean species; studies in the northern Pacific are relatively limited. Using microsatellite markers, the population genetics of Acropora sp. 1 was examined between two regions in Japan, the Okinawa-Aka and Bonin Islands, which are separated by approximately 1,500 km of open water in a high-latitude area. Statistically significant but small genetic differentiation in Acropora sp. 1 was detected between and within these regions. Genetic diversity was not obviously reduced in populations of the Bonin Islands, which are relatively isolated. Thus, some level of connectivity appears to be maintained between the two regions, likely because of the high dispersal ability of this broadcast spawner. [ABSTRACT FROM AUTHOR]

In 2007, high-temperature-induced mass coral mortality was observed in a well-developed fringing reef area on the southeastern coast of Ishigaki Island, Japan. To analyze the response of the corals to thermal stress, the coral cover was examined using Quickbird data, taken across the reef flat just before and after the bleaching event and performing a reef scale horizontal 2-dimensional thermal model simulation. The Quickbird data consisted of multispectral (MSS) imagery, which had a spatial resolution of 2.4 m, and panchromatic (PAN)-fused multispectral imagery, which had a 0.6-m spatial resolution. The observed changes in coral cover implied that the delineation of partially bleached coral was more precise with PAN + MSS. The classification accuracy achieved using PAN + MSS (93%) was superior to that obtained using MSS (88%). The in situ water temperature observations and 2-dimensional thermal model simulation results indicated that the water temperature fluctuated greatly in the inner reef area in late July 2007. Different thermal stress indices, including daily average temperature, daily maximum excess temperature, and daily accumulated temperature, were examined to define a suitable index that represented the severity of the thermal stress on coral cover. The results suggested that the daily accumulated temperature that occurred during the maximum sea surface temperature period of the bleaching season provided the best predictor of bleaching. The changes in water temperature, bathymetry, and coral patch size affected the severity of bleaching; therefore, the spatial dependence of these variables was examined using Moran's I and Lagrange multiplier tests. An investigation of the effect of coral patch sizes on coral bleaching indicated that large coral patches were less affected than the small patches, which were more likely to suffer bleaching and coral mortality. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the effect of acidified seawater on calcification and symbiotic algae (zooxanthellae density, chlorophyll content per single algal cell, fluorescence yield (Fv/Fm)) on a massive coral, Porites australiensis, a common species in the Ryukyu Archipelago of Japan. We found that acidified seawater significantly decreased the calcification and fluorescence yield, but did not affect zooxanthellae density and chlorophyll content per single algal cell. This indicates low levels of photoacclimation to acidified seawater in this species, and this is contrary to the findings of previous studies of Acropora species. A significant correlation between calcification and fluorescence yield was observed, indicating the presence of a strong relationship between calcification and algal photosynthesis. Our results indicate that endosymbiont photosynthetic dysfunction may enhance the decrease of coral calcification in future acidified ocean conditions. Calcification and fluorescence yield among colonies clearly differed, showing that the response to acidified seawater is highly variable among colonies in natural coral populations. [Copyright &y& Elsevier]

The Indo-Pacific zooxanthellate scleractinian coral genus Montipora is the host of many coral diseases. Among these are cyanobacterial Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs), but in general data on both diseases are lacking from many regions of the Indo-Pacific, including from Okinawa, southern Japan. In this study, we collected annual prevalence data of Black Band Disease (BBD) and Skeletal Growth Anomalies (GAs) affecting the encrusting form of genus Montipora within the shallow reefs of the subtropical Sesoko Island (off the central west coast of Okinawajima Island) from summer to autumn for four years (2017 to 2020). In 2020 Montipora percent coverage and colony count were also assessed. Generalized Linear Models (GLM) were used to understand the spatial and temporal variation of both BBD and GAs in the nearshore (NE) and reef edge (RE) sites, which revealed higher probability of BBD occurrence in RE sites. BBD prevalence was significantly higher in 2017 in some sites than all other years with site S12 having significant higher probability during all four surveyed years. In terms of GAs, certain sites in 2020 had higher probability of occurrence than during the other years. While the general trend of GAs increased from 2017 to 2020, it was observed to be non-fatal to colonies. In both diseases, the interaction between sites and years was significant. We also observed certain BBD-infected colonies escaping complete mortality. BBD progression rates were monitored in 2020 at site S4, and progression was related to seawater temperatures and was suppressed during periods of heavy rain and large strong typhoons. Our results suggest that higher BBD progression rates are linked with high sea water temperatures (SST > bleaching threshold SST) and higher light levels (>1400 µmol m−2 s−1), indicating the need for further controlled laboratory experiments. The current research will help form the basis for continued future research into these diseases and their causes in Okinawa and the Indo-Pacific Ocean. [ABSTRACT FROM AUTHOR]

Some coral species are more resistant than others to environmental factors that cause bleaching and bleaching-related mortality. This study compared aspects of the coral/zooxanthellae symbiosis in species and genera that suffered either high or low mortality during a bleaching event. These characteristics were assessed in Okinawa between March and June 1999, 5-10 months after the bleaching event there in August-September 1998. Species with low mortality rates generally had higher densities of zooxanthellae per square centimeter and a very low rate of release of degraded zooxanthellae. Low-mortality species also had more total coral tissue per square centimeter of coral surface area. The size of zooxanthellae varied little among species. The differences in these characteristics among coral species suggest that the symbiotic relationship operates very differently among coral species. [ABSTRACT FROM AUTHOR]

In temperate seas, expansion of reef-building coral distribution, decline of macroalgal beds, and changes in constituent species for coral communities and/or macroalgal beds mainly due to increase in sea surface temperature have been reported. Not only mitigation but also adaptive responses are important for the measures against climate change. Consideration of adaptive measures depends on local conditions such as the degree of environmental change and industrial structure is necessary when measures are implemented. This study focused on the marine protected area (Ashizuri-Uwakai National Park in Japan) and its surrounding area. This area is characterized by a very large north-south gradient in water temperature and the distribution of corals and macroalgae along it. The purpose of this study is to consider what adaptive measures are suitable for each region and industry in response to changes in coastal ecosystems (coral community and macroalgal bed). Future (assuming the end of this century under RCP2.6 and RCP8.5 scenarios) changes in the potential distribution area of coral, macroalgae, and their consumers were projected using simulated sea surface temperature with a high-spatial resolution. After projecting the coastal ecosystem changes and assessing the contemporary use of coastal ecosystem, we give examples of what specific adaptive measures should be taken in each area for three fields, i.e., biodiversity conservation, fisheries, and tourism. Assuming the 2090s, though drastic changes in coastal ecosystem are not projected compared to the present state under RCP2.6 scenario, as coral distribution shifts north, feeding damage by crown-of-thorn starfish is projected to become a problem. Therefore, expansion of protected areas and promotion of conservation activities are major challenges for coral ecosystem conservation. On the other hand, under RCP8.5 scenario, it is important to take appropriate conservation measures for macroalgae since coral growth becomes difficult to achieve and grazing pressure on macroalgae increases due to extreme elevated water temperature. Moreover, creation of alternate or new tourism resources will be needed. This research represents projected scenarios of coastal ecosystem changes with a high spatial resolution and adaptation measures based on the changes for each municipality. [Display omitted] • Adaptation strategies were considered for a temperate marine protected area. • Use, conservation and perception of coastal ecosystems varied across municipalities. • Shifts in coral and macroalgal distribution are projected based on water temperature. • Drastic ecosystem transition will occur under high emission scenario. • Implementation of adaptive measures depending on ecosystem changes is needed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel clade (genus level cluster) of dinoflagellate family Symbiodiniaceae was found. • Novel 110 sequence types were found, and most of them were highly divergent from known Symbiodiniaceae types. • Genetically divergent free-living Symbiodiniaceae communities were hidden at an isolated island in Japan. Dinoflagellates in the family Symbiodiniaceae are intensively investigated as algal symbionts of corals and other invertebrates, underpinning coral reef ecosystems as primary producers. Diversity, including regional diversification, of free-living communities is less studied. In this study, an environmental Symbiodiniaceae community at an isolated island, Okinotori Island, Japan, was investigated to determine whether the community is endemic or common with other locations near continents and major ocean currents. Symbiotic algae in common corals at the island were the same type as those of the corals from other Japanese waters. In the environmental samples, genera Symbiodinium (formerly clade A), Cladocopium (clade C), Durusdinium (clade D), and clades F (including Freudenthalidium), G, and I, were identified through analysis of internal transcribed spacer region 2 of nuclear ribosomal RNA gene (ITS2) sequences. Interestingly, some sequences found were genetically different from those of previously reported genera/clades. These unknown sequences were genetically included in the Symbiodiniaceae linage, but they were differentiated from the previously known nine clades. The sequences formed a cluster in the phylogenetic tree based on 28S nrDNA. These sequences were thus considered members of a novel clade in the family (clade J). In total, 120 kinds of ITS2 sequences were produced; while 10 were identical to previously reported sequences, the majority were highly divergent. These genetically unique Symbiodiniaceae types, including novel clade J, may have evolved in isolation and reflect the environmental characteristics of the Okinotori Island. [ABSTRACT FROM AUTHOR]

Increased seawater temperature has resulted in mass coral bleaching events globally. Acropora tenuis , the dominant hermatypic coral species in southern Japan, was exposed to four temperature treatments [28 °C, 30 °C, 32 °C, and >32 (=33.3 °C)] for 7 d. The coral colour was converted to R (red), G (green), and B (blue) values, each ranging from 0 (darkest) to 255 (brightest). RGB values exposed to 28 °C and 30 °C decreased slightly, whereas those exposed to 32 °C increased significantly after day 3–6, and those exposed to 33.3 °C changed to white within 2 d. Quantitative RT-PCR analysis revealed no significant changes in heat shock proteins in Acropora and symbiotic dinoflagellates at 28 °C and 30 °C after a 7 d exposure. Our findings revealed that 30 °C, higher than the mean temperature of the warmest month in southern Japan, was an inhabitable temperature for A. tenuis. [ABSTRACT FROM AUTHOR]

The article examines projects that are being enacted to restore the vitality of coral reefs in various parts of the world. Due to a process known as bleaching, 19% of the reefs on Earth have been destroyed, and a report from the Global Coral Reef Monitoring Network suggests that another 15% could be lost. While restoration ecology efforts in Japan’s Sekisei Lagoon and a costal community of the Philippines seem to have been successful, some experts are skeptical that the process will make much of a difference. University of Philippines marine biologist Edgardo Gomez provides quotes.

We report the isolation and characterization of eight microsatellite loci from the scleractinian coral, Acropora nobilis. The microsatellite loci were obtained using compound SSR primers or an enrichment protocol. All the loci were polymorphic with four to eight alleles per locus and observed heterozygosities ranging from 0.22 to 0.76. Some of the primers developed for the two congeners, Acropora palmata and Acropora millepora were applicable to A. nobilis. These loci are useful for studying the connectivity among A. nobilis populations in Okinawa, southern Japan. [ABSTRACT FROM AUTHOR]

The article presents a study on the new symptoms for Turbinaria in Japan. It mentions a white syndrome affecting colonies of Turbinaria peltata in tropical regions. Such syndomes include environmentally induced bleaching, predation by crown-of-thorns starfish, and outbreaks of coral-eating gastropods.