Coral Reef Areas Research Articles

Insight into the metabolic potential and ecological function of a novel Magnetotactic Nitrospirota in coral reef habitat.

Magnetotactic bacteria (MTB) within the Nitrospirota phylum play important roles in biogeochemical cycles due to their outstanding ability to biomineralize large amounts of magnetite magnetosomes and intracellular sulfur globules. For several decades, Nitrospirota MTB were believed to only live in freshwater or low-salinity environments. While this group have recently been found in marine sediments, their physiological features and ecological roles have remained unclear. In this study, we combine electron microscopy with genomics to characterize a novel population of Nitrospirota MTB in a coral reef area of the South China Sea. Both phylogenetic and genomic analyses revealed it as representative of a novel genus, named as Candidatus Magnetocorallium paracelense XS-1. The cells of XS-1 are small and vibrioid-shaped, and have bundled chains of bullet-shaped magnetite magnetosomes, sulfur globules, and cytoplasmic vacuole-like structures. Genomic analysis revealed that XS-1 has the potential to respire sulfate and nitrate, and utilize the Wood-Ljungdahl pathway for carbon fixation. XS-1 has versatile metabolic traits that make it different from freshwater Nitrospirota MTB, including Pta-ackA pathway, anaerobic sulfite reduction, and thiosulfate disproportionation. XS-1 also encodes both the cbb3-type and the aa3-type cytochrome c oxidases, which may function as respiratory energy-transducing enzymes under high oxygen conditions and anaerobic or microaerophilic conditions, respectively. XS-1 has multiple copies of circadian related genes in response to variability in coral reef habitat. Our results implied that XS-1 has a remarkable plasticity to adapt the environment and can play a beneficial role in coral reef ecosystems.

Analysis of The Conditions of Acropora Transplant Corals in "Liang" Bunaken National Park, North Sulawesi Province

Coral transplantation is the grafting or cutting of live corals to be transplanted elsewhere or where the corals have been damaged, aiming for restoration or the formation of natural coral reefs. Coral transplantation plays a role in accelerating the regeneration of coral reefs that have been damaged and can also be used to build new coral reef areas that previously did not exist. Meanwhile, the objectives of the research are: To describe the initial conditions, artificial coral transplantation in Liang, at the Bunaken National Park location; Analyzing the number of transplanted corals that survived for 3 years; Analyzing the condition of transplanted corals by measuring the length and number of coral branches that survived for 3 years. The results obtained for coral transplantation carried out in "Liang" Bunaken National Park, from 84 transplanted in 7 Modules, 76 coral fragments survived, and only 8 coral fragments died, with a 90% survival percentage. The average value of the increase in height of transplanted coral fragments was 10 cm, and the number of branches that increased in each coral fragment was an average of 11 branches in each surviving coral fragment. This means that from 2018 to 2021, the increase in height and number of branches is around 3 cm per year.

Climate Change and the Change of Trophic Level Interaction in Coral Reefs Based on South China Sea in China

In recent years, coral reefs have been seriously affected by human and natural factors, some of influences are even irreversible. Among them, the impacts of climate change have gradually deepened and attracted people's attention. Other papers which tell about the familiar topic failed to focus on discussing specific questions in certain area of coral reefs. The paper mainly analyzes the interspecific relationship change when facing the climate change of coral reef ecology in the South China Sea. Content of this paper first discusses the severe condition of climate change, like the instability of global climate system. Also, the situation about South China Sea and the effects of climate change are discussed and analyzed. Then, the interspecific relationships of predation, competition, parasitism, and mutualism were discussed. Further, discussed the increase of benthic algae and symbiotic organism reactions. The response from higher trophic level to low level and some researches are determined, too. On this basis, consider the interspecific relationships in the same trophic level. In the future, higher trophic level changes should be determined. Also, people should focus on the change after coral reefs recovering from albinism, about whether their population would change even extinct with the effect of climate change on coral reefs and reefs make a response to it through trophic level relationship change. This paper can provide some corresponding research ideas for more future researches.

Meso-mechanical anisotropy and fracture evolution of reef limestones from the Maldives Islands and the South China Sea

Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conventional rocks both in terms of rock structure and mechanical properties. In this study, mesoscale uniaxial compression experiments with five different loading directions were conducted on two kinds of reef limestones from the Maldives Islands and the South China Sea, respectively. The real-time high-resolution videos and images of failure processes were recorded simultaneously to investigate the fracture evolution and fracture surface roughness of reef limestones. It demonstrated that the reef limestones belonged to extremely soft to soft rocks, and their uniaxial compressive strength (UCS) values fluctuated with high discreteness. The mesoscale mechanical properties of reef limestones were highly anisotropic and mainly controlled by pore structure. The occurrence of dissolution pores in reef limestone tended to intensify mechanical anisotropy. With the integration of the fracture initiation and propagation features of reef limestones, it is supposed that the intrinsic mechanism of anisotropy was probably attributed to the differences in coral growth direction and dissolution. Furthermore, the quantified fracture surface roughness was revealed to have a good consistency with density and UCS for the reef limestones from the South China Sea. The findings are helpful for providing theoretical and experimental references for engineering construction in coral reef areas.

Seamount coral reefs are egg case nurseries for deep-sea skates.

Egg case nurseries of the boreal skate (Amblyraja hyperborea) and Richardson's skate (Bathyraja richardsoni) were defined and mapped on a bathyal seascape (~500-1,900 m depths) south of Tasmania, Australia, using 99 towed-camera transects (157 linear km; N= 50,858 images). In total, 738 skate egg cases were observed (present in 240 images, absent in 50,618); among 113 egg cases examined to identify parent species, 70% were A. hyperborea, 10% B. richardsoni and 20% unidentified Bathyraja species. 'Recently laid' egg cases were differentiated from 'aged' by classifying their colour and condition. The great majority (98%) of egg cases were observed in ~1,100-1,400 m depths on seamounts (15 of 36 surveyed), not seamount bases or adjacent continental slope. Egg cases were associated with reefs formed by accumulated skeletal matrix of the stony coral Solenosmilia variabilis, with >90% egg cases (including most of those recently laid) observed on living S. variabilis that characterises a 'coral zone' in ~950-1,350 m depths. Water in the coral zone is warmer (+0.66 to 2.37°C) than at the deep distributional limits of adult A. hyperborea and B. richardsoni (2,000 and 3,000 m, respectively), potentially providing for accelerated embryonic development. Co-occurrence with living coral infers an energetically favourable local-scale hydrodynamic environment for egg cases, particularly on seamount peaks, where increased water flow over egg cases would avert smothering by suspended sediment, and compensate for lower oxygen concentration compared to deeper depths occupied by adult skates. Criteria identifying egg case nurseries are strongly met for A. hyperborea at Seamount Z110 (468 egg cases of varied ages, maximum density of 5.47 m-2 ) and to a lesser extent on five others (Seamounts K1, Z16, Hill U, Z5 and Hill V). An abundance (density) criterion for defining nurseries needs to be flexible because it is a spatially scale-dependent measure that differs between surveys according to the tools and design employed. Off Australia, coral reef egg case nursery habitat is restricted to a narrow depth range in temperate latitudes where it is scarce and impacted by historical bottom trawl fishing in many locations. There has been effective conservation of nursery habitat, however, because four of the six nursery sites identified here and extensive coral reef areas are protected within marine parks. This article is protected by copyright. All rights reserved.

Taxonomical and functional analyses of epifaunal polychaetes associated with Mussismilia spp.: the effects of coral growth morphology.

The increasing habitat heterogeneity and complexity shows positive effects over different communities, leading to environmental diversity, access to resources and reducing the effectiveness of predation. In the present study we evaluate the structural and functional patterns of polychaete assemblages of three Mussismilia species with different coral morphology. Mussismilia hispida has a massive growth pattern; M. braziliensis also is a massive coral but forms a crevice in the corallum base; and M. harttii has a meandroid pattern. Ten individuals of the three Mussismilia species were sampled in two reefs in the Todos-os-Santos Bay, and we analyzed the differences in richness and abundance of polychaete species and the functional diversity metrics: Rao's quadratic entropy, functional dispersion, functional evenness, number of functional groups and functional richness, among Mussismilia species. Two-way ANOVA with permutations showed significant differences for polychaete abundances and richness among Mussismilia species (higher values for M. harttii), but no differences were recorded when compared between the two coral reef areas studied. There was no statistical difference among coral species or between reefs in relation to the functional diversity components influenced by abundance, such as Rao quadratic entropy, functional dispersion, and functional evenness. Some individual polychaete functional traits presented differences among Mussismilia species, and that also helped us to build a picture about the effect of different growth structures over functional aspects of polychaete assemblages. Thus, the taxonomical approach, the analysis of individual functional traits and the functional diversity metrics are fundamental tools to characterize the assemblage of organisms associated with corals.

Changing Trends in Temperatures and Rainfalls in the Western Pacific: Guam

Pacific islands have always been at the front of the great challenge of climate change. In this study, Mann–Kendall’s tau-based slope estimator was implemented to detect statistical trends in daily maximum and minimum temperatures of 2 stations and daily rainfalls at 14 stations over Guam for the period of 1953–2021, respectively, with 17 climate change detection indices. Mann–Kendall tests were implemented to the detection indices with respect to different time frames (i.e., annual, two-seasonal, and four-seasonal). The p-values from Mann–Kendall tests were used to determine the strength of trends, and Sen’s slopes were applied for the magnitudes of trends. The temperature trend analysis results indicate that Guam’s climate is getting warmer year by year. The increasing magnitudes of a seasonal maximum of daily maximum temperatures during the dry season are 0.036 °C/year for the dry season and 0.025 °C/year for the wet season at Anderson Airforce Base, while 0.031 °C/year and 0.023 °C/year for the dry and wet seasons at Guam International Airport. Trend analyses for temperatures have indicated that temperature during April through June has been increasing rapidly compared to other seasons. Strong trends in seasonal total rainfall amounts and the number of wet days were observed from July through December. The increasing trends in extreme rainfall indices during January–March and July–September periods would aggravate water quality due to the more sediments since important ecological reserve areas and coral reef areas are linked to watersheds in southern Guam.

Percentage of Hard Coral Cover and Coral Recruitment on in Bangsring Beach, Banyuwangi Regency

One of the tourist attractions at Bangsring Beach is the condition of the coral reef ecosystem and unique marine biota that tourists can enjoy by snorkeling and diving. Based on research (Ekawati et al., 2021) using remote sensing, the area of live coral reefs on Bangsring Beach is as follows; 2005; 3.38, 2008; 2.61, 2011; 3.7, 2017; 3.98, 2020; 6.1 Ha). It can be said that the area of coral reefs increases yearly, although, in 2008-2011, it decreased by 32%. The results of the economic valuation explain that the (Total Economic Value) of the coral reef ecosystem in Bangsring Beach is 38.2 billion Rupiah/year or 2.9 billion Rupiah hectares/year. The use-value that has the largest economic value comes from tourism utilization of 25 billion or 60% of the Total Economic Value. The coral community structure includes Coral Branching, Coral Encrusting, Coral Massive, Coral Submaasive, and Coral Mushroom. Mushroom Coral is found solitary and shaped like a mushroom. The research data shows the average value of Bangsring Fish House cover is 82.5%. Fish house cover here is seen and assessed based on the presence of hard corals, soft corals, and algae. The average percentage of hard corals growing at the Bangsring Fish House was 30%, soft corals 21.5%, and algae 17.5%. Found 21 types of coral such as; Acropora, Favia, Turbinaria, Symphyllia, Goniastrea.

Status and temporal change in the distribution of seagrass beds and coral reefs in the waters of Phu Quoc islands, Kien Giang province

To assess the status and changes in the distribution of seagrass beds and coral reefs in Phu Quoc from 2005 to 2018, we utilized high-resolution multi-spectrum satellite images, aerial photographs, and Google maps. We collected data from three time periods: 2005 (using ASTER with 15 m resolution), 2010 (using SPOT5 with 10 m resolution), and 2018 (using SENTINEL-2 with 10 m resolution). We also conducted an accuracy assessment of 78 key sites in March-April 2019, representing corals (25 sites), seagrasses (28 sites), rocks (8 sites), and sand (12 sites) through SCUBA diving. The results showed that in 2018, the waters of Phu Quoc contained 513 ha of coral reefs and 10,035 ha of seagrass beds, with 290 ha of coral reefs and 9,185 ha of seagrass beds located within the Phu Quoc marine protected area. While the area of coral reefs remained stable between 2005 and 2018, the seagrass beds experienced a significant decline of 652 ha (6.1%), with most losses occurring at Bai Vong (501 ha; 4.69%), Ong Doi cape - Dam Ngoai island (55 ha; 0.52%), Mot Island and Vinh Dam (42 ha; 0.4% each), and Da Chong cape (12 ha; 0.12%). This decline is largely due to recent infrastructure development for community and tourism purposes, which has caused the degradation of seagrass beds.

Analysis of Changes in the Area of Coral Reef Cover on Samalona Island, Mariso District, Makassar City, South Sulawesi.

<b>Background and Objective:</b> Coral reefs on Samalona Island have been under pressure both by natural events and by human (anthropogenic) activities, which have caused area degradation. Research on changes in the area of coral reefs is urgently needed. Hence, the objective of this research was to determine changes in the area of coral reefs from 2017, 2020 and 2023 and to determine the percentage of coral reef cover on Samalona Island. <b>Materials and Methods:</b> The method used to determine changes in the area of coral reef is the (unsupervised) method using Sentinel 2-A imagery and processed with ArcMap 10.8 while determining the percentage of coral reef cover (UPT) and processing with CPCe software. <b>Results:</b> From the results of image processing, it was found that changes occur every 3 years, namely 0.22 Ha, while the results of the accuracy test from the results of image interpretation with a ground check were 87.44%. The results of the percentage of coral reef cover obtained at station I, amounted to 6.99%, at station II 20.55% and at station III, 29.39%. The percentage of coral reef cover on Samalona Island in poor condition refers to the Decree of the Minister of State for the Environment No. 4 of 2001 concerning standard criteria for damage to coral reefs. <b>Conclusion:</b> There is a change in the area of coral reefs on Samalona Island which is heading to a damaged or declining condition every three years from 2017, 2020 to 2023.

The Evolution of Coral Reef under Changing Climate: A Scientometric Review.

In this scientometric review, we employ the Web of Science Core Collection to assess current publications and research trends regarding coral reefs in relation to climate change. Thirty-seven keywords for climate change and seven keywords for coral reefs were used in the analysis of 7743 articles on coral reefs and climate change. The field entered an accelerated uptrend phase in 2016, and it is anticipated that this phase will last for the next 5 to 10 years of research publication and citation. The United States and Australia have produced the greatest number of publications in this field. A cluster (i.e., focused issue) analysis showed that coral bleaching dominated the literature from 2000 to 2010, ocean acidification from 2010 to 2020, and sea-level rise, as well as the central Red Sea (Africa/Asia), in 2021. Three different types of keywords appear in the analysis based on which are the (i) most recent (2021), (ii) most influential (highly cited), and (iii) mostly used (frequently used keywords in the article) in the field. The Great Barrier Reef, which is found in the waters of Australia, is thought to be the subject of current coral reef and climate change research. Interestingly, climate-induced temperature changes in "ocean warming" and "sea surface temperature" are the most recent significant and dominant keywords in the coral reef and climate change area.

Distribution And Potential Of Caulerpa Sp Around The Seribu Islands Waters, Jakarta

Caulerpa macroalgae is one of the biota that has many benefits, ranging from consumption to being used as a producer of superior products. Currently, the use of Caulerpa has been widely carried out in several areas, ranging from direct use to cultivation. The distribution of Caulerpa is quite wide in shallow habitats from the intertidal zone to the edge of the edge. Caulerpa is also spread in the waters of the Seribu islands which grows in the areas of seagrass beds and coral reefs. The utilization of Caulerpa in Seribu island has not been widely carried out, so data is needed to identify the potential for Caulerpa management. dentification of species, abundance, and ecological index is needed for initial data as a basis for the management and utilization of Caulerpa in Seribu island.

A review of the endoparasitic isopods (Epicaridea: Entoniscidae) from hermit crabs, including description of the new subfamily Diogenioninae and a new species of Paguritherium Reinhard, 1945 from the Philippines.

Entoniscid isopods (Entoniscidae) are obligate endoparasites of other crustacean species. They have an indirect lifestyle, usually with two hosts and multiple larval stages; as adults they are found living within decapod hosts. Hermit crabs were previously known to be definitive hosts of only two species of entoniscid parasites: Paguritherium alatum, from the east coast of the United States in Pagurus spp. and Diogenion vermifactus from the Red Sea in Diogenes senex. Little beyond the original descriptions of these species has been reported in the literature. Recently, two species of entoniscids were found parasitizing hermit crabs (mostly Calcinus spp.) collected from shallow water coral reef areas in the Philippines. The goal of this study was to describe the morphology of both the adult and larval stages of these entoniscids through light and scanning electron microscopy and compare them to the previously described species that infest hermit crabs. One of these entoniscids is tentatively identified as D. vermifactus, which infested 0.95% (5 of 527) of the hermit crabs sampled. All specimens of D. cf. vermifactus were found in the abdomens of specimens of Calcinus gaimardii, C. minutus, C. pulcher and Pagurojacquesia polymorpha. Examination of D. vermifactus shows that this taxon belongs in its own subfamily: Diogenioninae n. subfam. The second entoniscid is a new species of the genus Paguritherium and infested 0.94% (7 of 744) of the hermit crabs (C. gaimardii and C. latens) sampled. Females of P. manggagaway n. sp. are characterized by a highly vaulted head, a slender body and long pleopods and males by a blunt head and stump-like pereopods covered in scales; the new species can be distinguished from P. alatum based on the specialized fan-like setae on the first five pereopods of the epicaridium larvae. A key to all entoniscid genera is provided.

The carbon sink of the Coral Sea, the world's second largest marginal sea, weakened during 2006–2018

The latest reports show that the ocean absorbs approximately 26 % of anthropogenic CO2 and that the carbon sink of the global ocean (air–sea CO2 flux) is continually increasing, while variations in different marginal seas are complicated. The Coral Sea, the second largest marginal sea in the world, is characterized by a generally oligotrophic basin and borders the biodiversity hotspot of Great Barrier Reef. In this study, we proposed a semianalytical method and reconstructed the first high-resolution satellite-based pCO2 and air–sea CO2 flux dataset from 2006 to 2018 for the Coral Sea. This dataset performed well in the basin (RMSE<10 μatm, R2 > 0.72) and coral reef areas (RMSE<12 μatm, R2 > 0.8) based on validation by a massive independent dataset. We found that sea surface pCO2 is increasing (1.8 to 2.7 μatm/year) under the forcing of increasing atmospheric CO2, and the pCO2 growth rate in water is faster than that in the atmosphere. The combination of increasing sea surface pCO2, high pCO2 seawater from coral reef areas, and the low depletion capacity of the oligotrophic basin led to a gradual weakening of the carbon sink in the Coral Sea, with the 2016 carbon sink being 52 % of that in 2006. This weakening was more pronounced after strong El Niño events (e.g., 2007, 2010, and 2016), with the corresponding high SST and low wind speed further weakening the carbon sink. This understanding of the long-term change in the Coral Sea provides new insight on the carbonate system variation and carbon sink capacity evolution in seawater under increasing atmospheric CO2.

Overview and potential implementation of a marine protected area network between Colombia, Nicaragua, and Jamaica

The United Nations recommends increasing protected area coverage to 30% by 2030 through representative and effective networks of marine protected areas (MPAn). According to the International Union for Conservation of Nature (IUCN), the number of MPAs increased rapidly from 0.67% in 2000–7.4% by the end of 2018. Yet only around 5.9% of the world’s coral reef area is included within MPAs and the implementation of MPA networks in areas beyond national jurisdiction remains limited. Here we report results on the evaluation of the ecological criteria suggested by the IUCN for the potential implementation of a MPAn between Nicaragua, Jamaica, and Colombia on the southwestern side of the Caribbean Sea. We have reviewed the different legislative structures for protection in place and the international and regional agreements endorsed by Colombia, Nicaragua, and Jamaica in force in 2020, together with biophysical connectivity studies in the Caribbean basin. Results indicate that the three countries: (i) have similar ecosystems open to protection, (ii) have already developed different governance instruments to protect them, (iii) there is a coherence between permitted and prohibited activities that provides strong governance related support for the potential MPA network for all zoning categories and iv) have the legislation and common ground to lead a successful implementation. The study concludes that the establishment of an MPA network in the southwestern part of the Caribbean will be advantageous for the protection of other marine ecosystems in the basin, addressing transboundary issues by focusing on connectivity and the already established MPA.

Global analysis of benthic complexity in shallow coral reefs

Three-dimensional shallow benthic complexity (also known as benthic rugosity) reflects the physical conditions of shallow coral reefs environments and can be used to estimate fish biomass and coral cover on reefs. Spatially explicit data on benthic complexity could offer critical information for coral reef conservation and management. However, benthic complexity has not yet been mapped at a global scale. We mapped global shallow water benthic complexity to 20 m depth at a spatial resolution of 10 m using 22 000 Sentinel-2 satellite images and a globally applicable underwater algorithm. We quantified geographic variation of benthic complexity in shallow coral reef areas from individual reef to ocean basin scales. We found that shallow benthic complexity is unevenly distributed worldwide, with high benthic complexity regions found in areas known to have high levels of benthic biodiversity such as the Coral Triangle, Coral Sea, and Great Barrier Reef. Yet nearly 60% of detected coral reef regions (size = 61 156 km2) are not listed as protected under current marine protected plans. These unprotected regions include substantial reef areas of high benthic complexity that may harbor high levels of biodiversity. Our global coral reef benthic complexity map supports plans to improve marine protected areas, reef conservation, and management.

The Current Condition of Coral Reef and Fish Diversity in Gosong Island, Southwest Aceh

Highlight Research The current condition coverage percentage of coral reefs in the waters of Gosong Island was 55% Percentage of dead coral with algae founded on Gosong Island is 28% On Gosong Island there are 11 families, namely Acroporidae, Agariciidae, Faviidae, Fungiidae, Merulinidae , Mussidae, Dendrophylliidae, Oculinidae, Pectiniidae, Pocilloporidae and Poritidae Abstract The coral reef ecosystem is an important ecosystem; its existence has a very close relationship with the surrounding ecosystem and the reef fish community. The direct and indirect dependence of reef fish on coral reefs has become an important issue at the national and international levels. This study aimed to determine the characteristics of coral reef ecosystem conditions, the percentage of coral growth, identify the types of coral reefs, and the diversity of reef fish species on Gosong Island, Southwest Aceh. Coral reef biophysical characteristics were collected by measuring water quality, calculating the percentage of coral coverage using the Point Intercept Transect (PIT) method, and the abundance of reef fish using the Underwater Fish Visual Census (UFVC) method. The condition of average percentage of coral reefs in the waters of Gosong Island was in a good category (55%), found as many as 31 genera of hard corals included in the line transect. The percentage of base substrate that dominates other than live coral is dead coral with algae (DCA) of 28%. The average abundance of reef fish in Gosong Island waters is 11,260 ind/ha with an average reef fish biomass of 2074,095 kg/yield. The water quality results show good conditions for coral growth in location. Based on the analysis of the structure of the fish community found in the coral reef area, the results showed good results, so the research location became a good habitat for various types of fish associated with coral reef ecosystems on Gosong Island

Utilization of Bathymetry and Sea Surface Current Data for Coral Reef Habitats in The Karimunjawa Islands

Coral reefs are a unique ecosystem found in tropical seas, one of which is Indonesia. Indonesia has many types of coral reefs, one of the most abundant types of coral reefs in Indonesia is Acropora Humilis and Montipora Aquituberculata. Acropora humilis lives at a depth of 15-35m, shaped like a plate with thin branches. Meanwhile, Montipora aquituberculata lives at a depth of 3-15 m. The deeper the location of this reef, the branches will be longer and open. the shallower, the shorter the branches. To determine the area of coral reefs, parameters can be used, namely bathymetry data and current velocity data. Bathymetry data and current velocity data were processed using the Kriging Interpolation. From the processing results, the depth value of Karimunjawa Islands waters is 0 – 76.06 masl, and the surface current velocity data for the Karimunjawa Islands is 0 – 0.55 m/s. The depth value is used to determine the coral reef habitat area of the two types of coral reefs studied, namely the coral reef type Montipora aquituberculata at a depth of 3-15 m and coral reef type Acropora humilis at a depth of 15-35 m. The value of the current velocity according to the coral reef habitat is 0.9 m/s while the value of the current velocity in the Karimunjawa Island is 0 – 0.55 m/s, it is said that the current value in Karimunjawa is suitable for the growth of coral reef habitat. The area obtained was found to be 878.268 Km2 of coral reef habitat area of Montipora aquituberculata and Acropora humilis.

Evaluating annual severe coral bleaching risk for marine protected areas across Indonesia

Coral reefs face an uncertain future under global climate change, with thermal-induced bleaching increasing in frequency such that corals will soon experience annual severe bleaching (ASB). Marine Protected Areas (MPAs) are therefore becoming increasingly important as a conservation tool. Here we evaluate (i) Indonesia’s coral reefs’ spatial variation in ASB, (ii) whether reefs projected to have a later onset of ASB (i.e. possible climate refugia) are protected within MPAs, and (iii) the ASB risk profiles for reefs related to MPAs receiving priority investments. Our results highlight considerable variability across Indonesia’s reefs being at risk of ASB. The ASB risk before 2028 is greater for coral reefs protected by MPAs versus those outside MPA boundaries. The ASB risk before 2025 is greater for coral reefs protected by priority MPAs versus those protected by non-priority MPAs. Overall, our results show that only ∼45% of the coral reef areas that are currently located within MPAs will likely act as thermal refugia (ASB > 2044). This is unsurprising given that the MPA network in Indonesia has been established over many decades, with most MPAs designated before suitable bleaching risk projections were available to inform MPA placement. Our results highlight the scope to further incorporate potential climate refugia for reefs into new MPA designations. This study also provides strategic information, which can support the development of Indonesia’s long-term MPA and coral reef conservation strategy to effectively manage, mitigate, and adapt to the impacts of climate change on coral reefs.

High diversity of benthic cyanobacterial mats on coral reefs of Koh Tao, Gulf of Thailand

Benthic cyanobacterial mats are increasingly reported to cover major coral reef areas. Although suggestions have been made that cyanobacterial mats impair coral reef health in multiple ways, information is lacking regarding the distribution, morphotypical variation and bacterial species composition of these microbial mats. As such, this study aimed to (1) Reveal the bacterial community diversity and composition of different mat morphotypes, (2) Identify the most abundant community members and closely related organisms, (3) Assess to what extent, morphotype, colonized substrate (coral or abiotic substrate), depth, and site were significant predictors of bacterial composition. Data were collected on reefs surrounding the island of Koh Tao (Gulf of Thailand). A total of 201 mats from 16 different locations around the island were classified into eight distinct morphotypes. Of these, the bacterial communities of 44 mats, representing colour groups from multiple sites, were characterized using 16S rRNA gene high-throughput sequencing. Our data revealed that Proteobacteria, Cyanobacteria, Bacteriodetes and Planctomycetes were the four most abundant phyla and occurred in all samples. Abundant cyanobacterial zero-radius operational taxonomic units (ZOTUs) were closely related to prokaryotic sequences found in previous studies of coastal mats (98–100%) and were assigned to genera in the order Oscillatoriales, e.g. Hormoscilla, Okeania, and Oscillatoria. Abundant proteobacterial ZOTUs were assigned to orders in the classes Alpha- and Gammaproteobacteria, e.g. Rhodobacterales, Rhizobiales and Alteromonadales. Abundant Bacteriodetes ZOTUs were mainly assigned to the class Bacteroidia and order Cytophagales. Our results showed that mats consist of a diverse and variable bacterial consortium, with mat colour (morphotype), substrate type and geographic location only explaining a small part of the total variation in composition.