Coral Reef Islands Research Articles

I saw the “atoll sign” – and now I need a tropical vacation

The atoll sign describes ring-shaped opacities surrounding central ground glass attenuation seen on chest CT and was first associated with organizing pneumonia. The name is derived from the Maldives' language, denoting a ring or crescentic-shaped coral reef island surrounding a central lagoon. Although biopsy is usually required for diagnosis, understanding some of the more common pathologies associated with the atoll sign may help narrow a differential and guide management.

Sustainability assessment for an offshore coral reef island based on scenario simulation and emergy analysis

As the intensity of ocean spatial exploitation increases, the offshore island tourism has been thriving, and the utilization of uninhabited islands is attracting more and more attention. In order to achieve the sustainable development of offshore island tourism resources, it is important to evaluate population carrying capacity and conduct sustainability assessment for uninhabited islands. To this end, we proposed a quantitative evaluation method for the sustainable development of offshore coral reef islands based on the combination of scenario simulation and emergy analysis. This method was tested on a coral reef island in the South China Sea, namely Lingyang Reef. The dynamics in emergy related structures and indicators of Lingyang Reef system were revealed under different scenarios, providing decision-making references for the pre-development sustainability assessment of an uninhabited coral reef island. The evaluation results showed that (1) when accommodating 2000 persons, the island system was in a low-load state, with sustainable values in terms of renewable energy input percentage, environmental load ratio, and emergy sustainability index, except for the critical state of emergy yield ratio; (2) when accommodating 5000 persons, the emergy yield ratio was in an unsustainable state, with the emergy sustainability index in a critical state, and both of the renewable energy input percentage and environmental load ratio in sustainable states, indicating that socioeconomic activities were not beyond the carrying capacity, and the development and utilization intensity was moderate; (3) when accommodating 10000 persons, the renewable energy input percentage and emergy sustainability index were in critical states, and the emergy yield ratio and environmental load ratio were in unsustainable states, indicating that the corresponding human activities had exceeded the carrying capacity.

Land Use Development of Bahuluang Island as a Leading Tourism Object in Selayar Regency, South Sulawesi

The Republic of Indonesia is an archipelagic country made up of 16,771 islands. The 314 islands are within the administrative area of ​​South Sulawesi Province. Bahuluang Island in the Selayar Islands Regency is one of them, which has rare resources that have not been utilized optimally as a source of driving the economy for the welfare of the people. This island has coral reef islands, white sand islands, and beautiful white sand beaches. Its natural conditions are very attractive and have the potential to be developed into a world-class tourist area. What is the academic perspective on the potential of this island to become a world-class tourist area, and how the development concept is right for it is a research problem. The aim is to reveal the potential and strategy for developing the area and its development model to become a world-class maritime potential-based tourism area. The method used is logical argumentation analyzed using the SWOT method. The results of the study revealed that Bahuluang Island has the potential to be developed into a marine tourism area with an all-in-one tourism concept. Its natural tourism landscape has the potential to create purely natural, traditional, modern, to extreme tourism activities. The existence of great opportunities for all-around tourism on this island can be presented side by side with marine tourism in the scarcity of coral islands and white sand islands to become world-class tourist areas. The potential of human resources as island property owners is a sizeable asset in supporting the presence of a tourist area in its place. The development strategy can be carried out by involving the community as the main part as owners of capital, which are protected by the management and control authority of the area and driven by third parties from investors together with supporting institutions in the protection of the Government of the Republic of Indonesia. The concept of building facilities must become a rare world tourism tour.

The Condition of Coral Reef Ecosystem for the Suitability of Dive Tourism Utilization in Karimunjawa Island, Karimunjawa National Park, Jepara

The Condition of Coral Reef Ecosystem for the Suitability of Dive Tourism Utilization in Karimunjawa Island, Karimunjawa National Park, Jepara

Seabird and reef conservation must include coral islands

Tropical seabirds exert key roles in reef ecosystems but face growing threats from climate change, especially on coral reef islands (CRIs). Therefore, we advocate for a more comprehensive, global data exchange on CRIs and CRI-dependent seabirds and outline steps for improving their study and conservation.

STRUKTUR KOMUNITAS IKAN DAN TERUMBU KARANG PULAU TUNDA, KABUPATEN SERANG, BANTEN

Tunda Island is one of the leading marine destinations in Banten Province which has high potential biodiversity. This study aimed to determine the health condition of the Tunda Island coral reef ecosystem. The method used in this study was Line Intercept Transect (LIT) method for coral reef and Belt Transect method for reef fish. Based on coral reef survey, the percentage of coral coverage on Tunda Island was 34.7%. From this value the coral reefs of Tunda Island were included in the sufficient category. The results of a survey of fish showed that there were 57 species from 17 families, which is dominated from Pomacentridae. The diversity index value (H ') of reef fish was 3.143, which showed that the diversity of reef fish around Tunda Island was high, and the uniformity index value (e) was 0.777, which showed that in Tunda Island waters the spread of fish species was stable.

Reef islands have continually adjusted to environmental change over the past two millennia

Global environmental change is identified as a driver of physical transformation of coral reef islands over the past half-century, and next 100 years, posing major adaptation challenges to island nations. Here we resolve whether these recent documented changes in islands are unprecedented compared with the pre-industrial era. We utilise radiometric dating, geological, and remote sensing techniques to document the dynamics of a Maldivian reef island at millennial to decadal timescales. Results show the magnitude of island change over the past half-century (±40 m movement) is not unprecedented compared with paleo-dynamic evidence that reveals large-scale changes in island dimension, shape, beach levels, as well as positional changes of ±200 m since island formation ~1,500 years ago. Results highlight the value of a multi-temporal methodological approach to gain a deeper understanding of the dynamic trajectories of reef islands, to support development of adaptation strategies at timeframes relevant to human security.

The evolution of Aotearoa New Zealand's policy discourses on Pacific climate mobilities from 2006–2021

In 2006 New Zealand government officials found themselves facing a barrage of enquiries arising from an erroneous claim contained in Al Gore's Academy Award-winning climate change documentary An Inconvenient Truth. The documentary suggested that the government of Aotearoa had agreed to take “all climate refugees” from Tuvalu, an archipelago of nine atolls and coral-reef islands in the South Pacific, as part of a planned response to climate change. At the time, New Zealand did not have any plan, or indeed any intention to create a plan, for addressing climate-induced displacement. The ensuing 15 years saw Aotearoa's official response evolve from one of “correcting misperceptions about New Zealand's position on climate-induced migration” to an adaptive development approach focused on Pacific-led solutions. This paper traces the evolution of that approach through a series of official reviews, focusing on the discursive frames and narratives that were employed by officials and government representatives. The current New Zealand government has expressed a desire to play a role in the development of world-leading approaches to climate-induced mobilities within the region, whilst it also seeks to avoid establishing overly broad policy precedents on climate migration that could apply beyond the Pacific. The paper discusses some of the avenues being explored by government departments, in particular the potential for existing temporary migrant programs to be developed into schemes that actively support an adaptive development framework in response to climate-related mobilities. We consider the range of possible solutions that could be contained within such a response, the opportunities for mutually beneficial approaches and the challenges that they would pose to long-accepted norms and processes embedded in the country's current immigration programs.

Development and Application of an Environmental Education Tool (Board Game) for Teaching Integrated Resource Management of the Water Cycle on Coral Reef Islands

To solve resource issues on coral reef islands, an understanding of the water cycle is essential. Water resource management is intricately linked to diverse occupational industries and coral reef ecosystems on these islands. To effectively promote sustainable natural resource management, we developed a board game as an environmental education and communication tool for school students and people of all ages. The concept of the game is that “clean water will always be available if it is used properly”. The board game was designed based on an island with an underground freshwater lens as its main water resource. Role-playing was used to enhance islander livelihoods such as with vegetable and livestock farming, fishing, and tourism. Players, while working collaboratively, have to use the island’s groundwater adequately and conserve it for future generations. The game was developed through a transdisciplinary process in collaboration with scientists, administrative officers, civic groups, and students. Additionally, the board game was tested in diverse communities. In this study, we elaborated on the board game after it was played by students at an elementary school on Tarama Island. We observed that participants learned that cooperation is important for the sustainable use of water resources. Moreover, the participants proposed two methods for cooperation: joint discussion and ‘assembly decisions’. The board game has the potential to be used as an effective environmental education tool to promote sustainable water resource management on coral reef islands.

Effects of ocean warming and fishing on the coral reef ecosystem: A case study of Xisha Islands, South China Sea

Global change has generated challenges for oceans, from individuals to the entire ecosystem, and has raised contemporary issues related to ocean conservation and management. Specifically, coral reef ecosystems have been exposed to various environmental and human disturbances. In this study, the Ecopath with Ecosim model was used to explore the impacts of ocean warming and fishing on Xisha Islands coral reef ecosystem in the South China Sea. The variables in this model included two ocean warming scenarios and three fishing scenarios. The model consisted of 23 functional groups including algae, coral, sea birds, and sharks. Our results showed that by the middle of the century, ocean warming and fishing led to a 3.79% and 4.74% decrease in total catch compared with 2009, respectively. In addition, the combined effects of ocean warming and fishing caused a 4.79% decrease in total catch, and the mean trophic level of catch was predicted to decrease by 6.01% under the SSP585-High fishing scenario. Reducing the fishing effort mitigates the effects of ocean warming on some species, such as large carnivorous fish and medium carnivorous fish; however, under low fishing effort, some functional groups, such as small carnivorous and omnivorous fish, have low biomass because of higher predation mortality.

Diversity of the Tabuhan Island coral reef fish revealed by DNA barcoding and implication on conservation strategy in Banyuwangi, Indonesia

Abstract. Sektiana SP, Abdillah AA, Alam JM, Isroni W, Dewi NM, Kim HW, Androyono S. 2022. Diversity of the Tabuhan Island coral reef fish revealed by DNA barcoding and implication on conservation strategy in Banyuwangi, Indonesia. Biodiversitas 23: 4844-4851. Tabuhan Island, Banyuwangi, Indonesia, is one of the mainstays of coastal tourism with the charm of coral reefs and has a fairly high potential for reef fish diversity. Coral reef ecosystems provide suitable habitats for reef fish to spawning ground, feeding ground, and nursery ground which provide suitable nurturing areas. Here, studies have been carried out on the diversity of reef fish by molecular approaches. The molecular identification approach provides accuracy in identification to the species level. In this study, samples of reef fish species from Tabuhan Island waters were identified molecularly in the mitochondrial DNA region of the cytochrome c oxidase subunit I (COI). The identification results showed that 53 specimens had been identified, and some of the themes were registered in the GenBank database to strengthen the genetic information of reef fish in the tropical region of Indonesia. A total of 53 specimens were identified, spread over 49 species, 3 orders, and 17 families dominated by reef fish groups from Labridae (20 species). The phylogenetic tree reconstruction shows that the family collects several species, but some species are classified as paraphyletic. The results of this molecular identification have also succeeded in registering 35 COI sequences in the Genbank database. The mtDNA sequence data is very important and becomes the basis for the genetic conservation resources in coral reef ecosystems.

Ecological Health Assessment of the Surface Sediments of the Coral Reefs of Khark and Kharko Islands (Persian Gulf, Iran)

Ecological Health Assessment of the Surface Sediments of the Coral Reefs of Khark and Kharko Islands (Persian Gulf, Iran)

Underwater Image Restoration via Contrastive Learning and a Real-World Dataset

Underwater image restoration is of significant importance in unveiling the underwater world. Numerous techniques and algorithms have been developed in recent decades. However, due to fundamental difficulties associated with imaging/sensing, lighting, and refractive geometric distortions in capturing clear underwater images, no comprehensive evaluations have been conducted with regard to underwater image restoration. To address this gap, we constructed a large-scale real underwater image dataset, dubbed Heron Island Coral Reef Dataset (‘HICRD’), for the purpose of benchmarking existing methods and supporting the development of new deep-learning based methods. We employed an accurate water parameter (diffuse attenuation coefficient) to generate the reference images. There are 2000 reference restored images and 6003 original underwater images in the unpaired training set. Furthermore, we present a novel method for underwater image restoration based on an unsupervised image-to-image translation framework. Our proposed method leveraged contrastive learning and generative adversarial networks to maximize the mutual information between raw and restored images. Extensive experiments with comparisons to recent approaches further demonstrate the superiority of our proposed method. Our code and dataset are both publicly available.

Lagoonal reef island formation in Huvadhoo atoll, Maldives, highlights marked temporal variations in island building across the archipelago

Coral reef islands provide the only pedestals of human habitation in mid-ocean atoll archipelagoes. Understanding the environmental controls on island formation is critical for evaluating the future response of islands to environmental change and sea-level rise. This study examines the evolution of lagoonal reef islands in Huvadhoo atoll, southern Maldives. Using extensive ground penetrating radar (GPR) imaging of island sediment structure, combined with comprehensive analysis of island morphology, sedimentology, and 49 radiometric dates, detailed reconstructions of the evolution of two lagoonal islands is presented. A four-stage model shows a complex history of island formation across various stages of sea-level change during the late-Holocene: 1) lagoon infill occurring from ~3000–2000 years ago during a period of sea-level fall from the mid-Holocene highstand; 2) emergence of the island core through vertical aggradation during the latter stages of sea-level fall between ~2000 and 1500 yBP; 3) rapid lateral expansion of the islands between 1500 and 500 yBP coincident with the availability of sand-size sediments and during a period of sea-level oscillation; and, 4) subsequent minor expansion and modification of island shorelines through alongshore reworking of island sediments over the past 500 years. Results provide evidence of marked differences in the timing and mode of island formation within Huvadhoo atoll. Significantly, the formation of the lagoonal islands post-dates the formation of islands on the atoll rim by 1000–2000 years. Furthermore, the formation of sand islands over infilled shallow lagoons contrasts the formation of most atoll rim islands through the sequential deposition of storm-generated rubble deposited directly across reef surfaces that have reached their vertical growth limit. Results of lagoonal island formation in the southern Maldives provide comparative data for the northern Maldives. While the sequence of island formation follows the faro infill model identified in the northern archipelago, lagoonal islands in the south appear to have formed 2000 years after those in the north. This difference is likely to reflect lagged reef growth response from deeper foundations in the southern archipelago.

Heightened storm activity drives late Holocene reef island formation in the central Pacific Ocean

The impact of global environmental change on coral reef islands is uncertain, with few studies having resolved the critical controls on island formation and change. Based on detailed, topographic surveys, sediment analysis and radiometric dating, we present a multi-phase model of the formation of two reef islands in Jaluit atoll, Republic of the Marshall Islands. The initial phase of island building occurred 1300 years ago, later than elsewhere in the Marshall Islands and during a period of relative sea level fall from the mid-Holocene sea level highstand . Initial accumulation occurred as a consequence of relative emergence of the reef flat that forced a transition in reef flat ecology and dominant foraminifera sediment producers that contributed to island building. Distinctive sets of progradational ridges and their coarse sediment character provide evidence for the importance of extreme wave events in island expansion from an initial core. Expansion occurred in two principle phases, 650–350 years ago and 200 years ago to the present, each coincident with known phases of increased storminess in the central Pacific. Results highlight the complexity of island formation and show that future change will depend not only on sea level but storm processes that have been a major influence on island development over the past 650 years. Anticipated reduction in cyclogenesis in the southern Marshall Islands region suggests a near-future period of geomorphic stasis of the islands of Jaluit. An increase in cyclogenesis in the central Pacific and higher latitudes may enhance opportunities for storm-driven island accumulation events over the next century where coral growth is able to be maintained. • Island formation in Jaluit atoll occurred over the past 1300 years, during relative sea level fall and subsequent stability. • Cyclonic events were critical in the episodic expansion of islands over the past 700 years. • Relative sea-level fall forced changes in reef ecology and sediment production and transport regimes for island accumulation. • Formation of islands in Jaluit atoll lagged other parts of the archipelago and post-date habitation of the Marshall Islands. • Reduced storm dynamics in the tropical western north Pacific suggests a future period of island geomorphic stasis.

Sea Ranching Feasibility of the Hatchery-Reared Tropical Sea Cucumber Stichopus monotuberculatus in an Inshore Coral Reef Island Area in South China Sea (Sanya, China)

Sea ranching of tropical edible sea cucumbers is an effective way to relieve the overfishing stress on their natural resources and protect the coral reef ecosystem, yet only a few species have been applied in the sea ranching practice based on hatchery-reared juveniles around the world. In this study, an 8-month (April to December) sea ranching study for hatchery-reared edible sea cucumber Stichopus monotuberculatus juveniles was carried out at a tropical coral reef island area in Sanya, China. Several growth performance indexes and basal nutritional components were monitored. Results revealed that the sea cucumbers had a growth rate of 0.35~0.78 mm day-1 during the experimental period, reaching 15.9 cm long before winter. The weight gain reached 491.13% at the end, and most sea cucumbers were able to grow to the commercial size (over 150 g WW) in the first year of sea ranching. The overall specific growth rate (SGR) and survival rates were 0.73 and 27.5%. Most of the death occurred in the first month after release (25.0%–37.5%), and this is probably due to inadaptation to the sudden change of the environment from the hatchery to the wild, which is proved by the remarkable decrease in nutritional indexes (amino acids, total lipid, and crude protein). Stable isotope and lipid biomarkers revealed that the food source mainly comes from water deposits (with microbes), Sargassum sanyaense seaweed debris, phytoplankton, and coral mucus-derived organics. The study proved the feasibility of the sea ranching of the hatchery-reared S. monotuberculatus juveniles in the tropical coral reef island area. Also, it is highly recommended that appropriate acclimation operation before release should be carried out to improve the survival rate of this species.

Identification of coral reef cover and invertebrate diversity in Pahawang Island Lampung Indonesia

Pahawang Island is one of Lampung's tourist attractions known for its high organism biodiversity. The diversity of coral reefs contained in it causes Pahawang to have economic value for the audience. This study aims to determine the coverage and condition of coral reefs in the Pahawang area as a tourist attraction and identify the diversity of organisms within. This study used the Line Intercept Transect (LIT) method by dividing the plot of the observation area by six (6) identification points for data collection. Measurement data on each line transect, furthermore the closing value is calculated. The number of species was calculated by determining the value of the invertebrate diversity index. The results showed that the length of coral cover on Pahawang Island was 80.3% which lies in the “very good” category. Most of the corals have experienced bleaching which suggests that the corals are not in healthy condition. Species diversity shows that eleven (11) species reside in the Pahawang Island coral reef. The Shanon-Wiener diversity index value (H') 1.87 is categorized at the medium level. Therefore, the condition of coral cover on Pahawang Besar Island is still in the very good category.

Bacterioplankton communities reveal horizontal and vertical influence of an Island Mass Effect.

Coral reefs are highly productive ecosystems with distinct biogeochemistry and biology nestled within unproductive oligotrophic gyres. Coral reef islands have often been associated with a nearshore enhancement in phytoplankton, a phenomenon known as the Island Mass Effect (IME). Despite being documented more than 60 years ago, much remains unknown about the extent and drivers of IMEs. Here we utilized 16S rRNA gene metabarcoding as a biological tracer to elucidate horizontal and vertical influence of an IME around the islands of Mo'orea and Tahiti, French Polynesia. We show that those nearshore oceanic stations with elevated chlorophyll a included bacterioplankton found in high abundance in the reef environment, suggesting advection of reef water is the source of altered nearshore biogeochemistry. We also observed communities in the nearshore deep chlorophyll maximum (DCM) with enhanced abundances of upper euphotic bacterioplankton that correlated with intrusions of low-density, O2 rich water, suggesting island influence extends into the DCM.

Bleaching Susceptibility and Resistance of Octocorals and Anemones at the World's Southern-Most Coral Reef.

Coral reefs are amongst the most biodiverse ecosystems on earth, and while stony corals create the foundational complexity of these ecosystems, octocorals and anemones contribute significantly to their biodiversity and function. Like stony corals, many octocorals contain Symbiodiniaceae endosymbionts and can bleach when temperatures exceed the species’ upper thermal limit. Here, we report octocoral bleaching susceptibility and resistance within the subtropical Lord Howe Island coral reef ecosystem during and after marine heatwaves in 2019. Octocoral and anemone surveys were conducted at multiple reef locations within the Lord Howe Island lagoon during, immediately after, and 7 months after the heatwaves. One octocoral species, Cladiella sp. 1, experienced bleaching and mortality, with some bleached colonies detaching from the reef structure during the heatwave (presumed dead). Those that remained attached to the benthos survived the event and recovered endosymbionts within 7 months of bleaching. Cladiella sp. 1 Symbiodiniaceae density (in cells per µg protein), chlorophyll a and c 2 per µg protein, and photosynthetic efficiency were significantly lower in bleached colonies compared to unbleached colonies, while chlorophyll a and c 2 per symbiont were higher. Interestingly, no other symbiotic octocoral species of the Lord Howe Island lagoonal reef bleached. Unbleached Xenia cf crassa colonies had higher Symbiodiniaceae and chlorophyll densities during the marine heatwave compared to other monitoring intervals, while Cladiella sp. 2 densities did not change substantially through time. Previous work on octocoral bleaching has focused primarily on gorgonian octocorals, while this study provides insight into bleaching variability in other octocoral groups. The study also provides further evidence that octocorals may be generally more resistant to bleaching than stony corals in many, but not all, reef ecosystems. Responses to marine heating events vary and should be assessed on a species by species basis.

Possible Tsunami-Induced Sediment Transport From Coral Reef to Deep Sea Through Submarine Canyons on the Southern Ryukyu Forearc, Japan

Submarine canyons are efficient sediment transport pathways from shallow marine areas to deep sea. Along active margins, large tsunamis are a trigger for sediment transport to deep sea. However, sediment transport through submarine canyons by such extreme wave events in the carbonate depositional environments has not been fully understood. Large tsunamis have repeatedly struck the coral reef islands of the southern Ryukyu Islands and have transported large boulders composed of coral from the reef to shore. In this study, we examined sediment cores collected near the mouths of submarine canyons and basin floor on the southern Ryukyu arc’s forearc. The presence of coarse calciturbidites containing coral, molluskan fragments, and coral reef benthic foraminifera was limited on the submarine fan formed at the mouth of the reef-connected and shelf-incised submarine canyon. In cores collected near the mouth of shelf-incised submarine canyons with no reef connection and slope-confined canyons, no coarse calciturbidite is observed. Few calciturbidites were found in more downslope cores, implying that most calcareous grains derived from shallow marine areas were deposited on this fan. Depositional intervals of turbidites were calculated to be several hundred–a few thousand years, which agree with the recurrence intervals of large tsunamis estimated from onshore tsunami deposits, based on radiocarbon dates in hemipelagic mud intervals. No temporal change in the depositional intervals of calciturbidites in the cores from the submarine fan since the last glacial maximum. Therefore, the tsunamis may be an important mechanism for surface sediment reworking in coral reefs, and shelf-incised and reef-connected submarine canyons can play an important role in the efficient transport of shallow marine calcareous grains to the deep sea.