Coral Reef Diversity Research Articles

Coral gardening in a changing climate: Rapid assessment of the 4th recorded bleaching event at the Anantara Lagoon and reef system, South Male Atoll, Maldives

Coral reefs are crucial to marine biodiversity and provide essential ecosystem services, but they face severe threats from climate change, particularly through coral bleaching events. The Maldives, renowned for its diverse coral reefs, has experienced increasing coral bleaching incidents, impacting both marine biodiversity and the tourism-dependent economy. This study investigates the effects of the 2024 coral bleaching event on coral nurseries within the Anantara Lagoon and reef system, South Male Atoll, Maldives. Monitoring was conducted across two coral nurseries in the lagoon and one coral nursery on the natural reef, focusing on species-specific responses to bleaching, predation, and survival rate. Results revealed variability in bleaching impacts among species and locations. Acropora aspera and Acropora muricata exhibited high mortality rates and increased predation, particularly at greater depths (~5 m), while Montipora digitata, Pocillopora damicornis, and Porites cylindrica showed greater resilience. The findings highlight the importance of adaptive management strategies for coral nurseries, emphasizing real-time environmental monitoring and strategic nursery placement to bolster coral reef resilience. This study underscores the need for integrated approaches combining coral restoration with broader reef management practices to enhance ecosystem recovery and sustainability

Cryptofaunal communities are influenced by benthic cover and fish abundance in a large Caribbean coral reef system

Small-sized invertebrates inhabiting hard substrates in coral reefs (a.k.a. cryptofauna) contribute substantially to reef biodiversity, but their patterns of distribution and ecological controls are poorly understood. Here, we characterized the cryptofauna community and explored “bottom-up” and “top-down” controls by benthic cover and fish abundance, respectively. We sampled the cryptofauna inhabiting the reef terrace from 13 sites along 200 km in Jardines de la Reina (Cuba), a well-preserved and protected area in the Caribbean. We counted 23,959 invertebrates of 14 higher taxa, being the most abundant Copepoda (54%), Nematoda (21%), Mollusca (7%), Ostracoda (5%), Polychaeta (5%), and Amphipoda (3%). Richness, abundance, and community structure varied across the reefs without any geographical gradient of distribution. One-third of the variance occurred at site scale (~ 10 km), and half occurred at quadrat scale (~ 1 m). Algal cover promoted cryptofauna richness and abundance likely providing substrate and food, while live coral cover negatively influenced nematode abundances, potentially due to coral defenses. Relationships between cryptofauna and reef fishes were also present, with invertivores and herbivores negatively affecting cryptofauna abundance likely due to direct or indirect predation pressures. This research highlights the important roles of bottom-up and top-down controls, by algal/coral cover and fishes, respectively, on cryptofauna and in extension to coral reef biodiversity. Current threats by climate change are expected to alter these controls on cryptofauna resulting in changes to diversity, trophodynamics and energy flows of coral reefs.

Comparing modeled predictions of coral reef diversity along a latitudinal gradient in Mozambique

IntroductionPredictive models based on environmental proxy data are being used to predict biodiversity on large and even global scales. Yet, some of the underlying assumptions about the relationship between proxy variables and predictions require investigations and testing the consequences of using model alternatives, data sources, variables choices, and scales, extent, and overlap among the predictions. Mozambican coral reefs provide a good case study to test these assumptions given the paucity of field data, its long coastline, and transitions from tropical to temperate environments.MethodsThree modelling formulations and 5 specific models were made using satellite and shipboard measurements and extensive fish and corals field data to test their performance in predicting numbers of fish species and coral taxa from field data. Model predictions were mapped for the 1180 ~6.25 km2 Mozambican coral reef cells. Predictions were made and mapped 1) based on ~1000 field sites in the Western Indian Ocean (WIO) faunal province model, 2) using environmental variable selected in the WIO model (WIOMOD) but trained only with Mozambican field data (<113 sites), and 3) using only Mozambican environmental and field data and standard variable redundancy and selection procedures.Results and discussionTraining and testing cross validation of models indicated modest predictive ability (R2~0.42-0.56%) and reasonable transferability. Consequently, there was unexplained variation likely due to small-scale environmental variability finer than the mapped cell scale. Differences between model predictions were caused by different variable rankings and response relationship. For example, the Mozambique-only model predicted more fish but fewer coral taxa, a larger role of water quality and sediments, habitats, and temperature variation, and a lesser role of human influence than the WIOMOD. Therefore, differences between models indicate that large scale models (i.e. provincial or global) can contribute to understanding gross patterns but miss important local environmental and human drivers in transitional environments. Nevertheless, 79% of the fish and 88% of coral taxa cell-level predictions of taxonomic diversity had standardized coefficients of variations of <10%.

The distribution of coral reef fish biodiversity on Bontosua Island, Spermonde Archipelago, South Sulawesi Province

Background: Bontosua Island, located in the Spermonde Archipelago, is one of the strategic and historical islands in the region. The island plays a vital role in ecosystem conservation efforts by the local community, who are committed to preserving their natural environment. With dynamic ecosystem conditions, it is essential to understand the seabed cover and biodiversity on the island to support more effective conservation efforts. Methods: This study was conducted from March to September 2022 to mark the seabed cover of Bontosua Island and understand the relationships between coral reef fish species and the ecosystem. The method used was a stationary visual census, followed by descriptive analysis and one-way ANOVA to assess the biodiversity and diversity of coral reefs. Findings: The results showed a total of 1,306 coral reef fish from 9 families with 63 species identified, including the families Chaetodontidae, Serranidae, Lutjanidae, Haemulidae, Lethrinidae, Scaridae, Acanthuridae, and Siganidae. The families with the highest citations were Scaridae, Acanthuridae, and Siganidae. The highest coral reef fish were found in the north, west, and southwest of the island, where live coral areas are more dominant. Conclusion: This study shows that Bontosua Island has significant coral reef diversity, and certain areas, such as the north and southwest sides, have higher reported fish. These findings indicate the importance of these areas in conservation efforts. Novelty/Originality: This study provides a comprehensive picture of the seabed cover and coral reef fish diversity in Bontosua Island, which has yet to be widely discussed in previous studies. These findings provide a scientific basis for more targeted conservation strategies and help improve understanding of the dynamics of coral reef ecosystems in the Spermonde Islands.. Novelty/Originality of this article: This study proposes developing a community-based coral reef monitoring system that integrates local knowledge with digital mapping technology, aiming to increase the effectiveness of conservation and management efforts of marine resources on small islands.

Variations in benthic coverage and diversity of shallow water coral reefs in Eastern coast of Sri Lanka: A combined analysis from Allen Coral Atlas and ground surveys

AbstractMonitoring changes in coral reef ecosystems for their conservation and management is important as they are frequently subject to various natural and anthropogenic threats. However, in Sri Lanka, the attention in this regard is to be further concerned for their well‐being. Therefore, this study focused on the selected shallow water (<5 m) coral reefs as Pigeon Island (PIR), Adukkuparu (AR), Salli Beach (SBR), Kayankerni (KR), and Passikuda (PR) on the Eastern coast of Sri Lanka to estimate their changes over 2020, 2021, and 2022. The remote sensing demarcations with the composition of reef ecosystems were done through the analysis of the Allen Coral Atlas data followed by field surveys. Higher accuracy levels for corals were obtained for each site due to field verifying all individual polygons and omitting unmatched polygons of the initial maps from the Allen Coral Atlas. Then, the in‐situ reef surveys were conducted over randomly selected permanent transects at each site. From 2020 to 2022, the live coral percentages have increased in PIR, AR, and SBR while reduced in KR and PR. Dead corals have facilitated the overgrowth of macroalgae. The combined area of live coral on all five reefs has slightly gone up. This increase is primarily due to the rise in live coral cover in AR and SBR. Also, prominent increments of coral diversity have resulted from those sites. Therefore, it is suggested that AR and SBR be designated as Marine Protected Areas to safeguard the newly emerging live corals.

Exploring the antibacterial potential of tunicate-associated bacteria (Ascidiacea) at the shipwreck site of Menjangan Kecil Waters, Karimunjawa

Menjangan Kecil Island is situated south of Karimunjawa Island and boasts a rich diversity of coral reefs and associated marine life, including tunicates. Tunicates, also known as sea squirts, produce secondary metabolites to defend against predators. This study aims to explore the antibacterial potential of tunicate-associated bacteria from shipwrecks in Menjangan Kecil Waters. The research adopts an exploratory descriptive approach. Seventy-two bacterial isolates were recovered from five tunicate specimens. Fifteen isolates exhibited antibacterial activity against Vibrio harveyi, with two isolates, KJ1.3.02.05 and KJ1.4.02.02, displaying the highest activity. Molecular identification via 16S rRNA gene amplification revealed that KJ1.3.02.05 was Sinomicrobium oceani (99.64% similarity), and KJ1.4.02.02 was Bacillus haynesii (98.64% similarity).

The Coral Chronicles: Climate Crisis and Its Implications on the Global Coral Reefs

The coral reefs are one of the most devastating causalities that is often overlooked as our planet grapples with the continually progressing crisis of climate change. They are often addressed as the rainforests of the sea and are hubs of biodiversity that support a one-fourth of all marine species even though they only cover less than one percent of the ocean floor. Not only are they inhabiting countless marine creatures, they are also a crucial food an income source to the millions of people worldwide. Alas! These vibrant underwater ecosystems are being pushed to the brink of collapse due the relentless onslaught of climate change. 
 Consider the Great Barrier Reef, off the coast of Australia, where extensive coral bleaching events are occurring due to rising sea temperatures [1]. The threat of ocean acidification has jeopardized the coral reef in the Maldives and is potentially affecting the country economically which is based on the tourism and fisheries. Likewise, Caribbean Sea is facing disease outbreak and coral bleaching. Philippines is home to some of the most diverse coral reefs in the world but, climate change, overfishing and coastal development is threatening these natural ecosystems. Apart from these, Seychelles and Mauritius in the Indian Ocean and the Coral triangle in the Southeast Asian region are also at stake due to these environmental stressors [2]. 
 In the face of these challenges, many governments, NGOs and local communities have united to conserve these global reefs. Different Marine Protected Areas (MPAs) have been developed to mitigate overfishing and habitat destruction and protect the coral reefs [3]. Moreover, many techniques have been developed to restore the degraded coral ecosystems and enhance their resilience, including Coral Transplantation and Artificial Reef Structures. These initiatives have created the hope that the vibrant coral reefs will eventually recover in face of the existing environmental crises. 
 However, we cannot overstate that the current situation is dire and nothing short of a global calamity. It is our moral obligation that we protect and preserve these natural wonders for future generations. If we do not take immediate action to curb the emission of greenhouse gases and fight against the climate change, we risk losing these underwater ecosystems right in front of our eyes. It is our choice and the stakes could not be higher. 

Modeling the spatial distribution of numbers of coral reef fish species and community types in the Western Indian Ocean faunal province

Predicting and mapping coral reef diversity at moderate scales can assist spatial planning and prioritizing conservation activities. We made coarse-scale (6.25 km2) predictive models for numbers of coral reef fish species and community composition starting with a spatially complete database of 70 environmental variables available for 7039 mapped reef cells in the Western Indian Ocean. An ensemble model was created from a process of variable elimination and selectivity to make the best predictions irrespective of human influences. This best model was compared to models using preselected variables commonly used to evaluate climate change and human fishing and water quality influences. Many variables (~27) contributed to the best number of species and community composition models, but local variables of biomass, depth, and retention connectivity were dominant predictors. The key human-influenced variables included fish biomass and distance to human populations, with weaker associations with sediments and nutrients. Climate-influenced variables were generally weaker and included median sea surface temperature (SST) with contributions in declining order from SST kurtosis, bimodality, excess summer heat, SST skewness, SST rate of rise, and coral cover. Community composition variability was best explained by 2 dominant community richness axes of damselfishes-angelfishes and butterflyfishes-parrotfishes. Numbers of damselfish-angelfish species were ecologically separated by depth, and damselfishes declined with increasing depth, median temperature, cumulative excess heat, rate of temperature rise, and chronic temperature stresses. Species of butterflyfish-parrotfish separated by median temperature, and butterflyfish numbers declined with increasing temperature, chronic and acute temperature variability, and the rate of temperature rise. Several fish diversity hotspots were found in the East African Coastal Current Ecoregion centered in Tanzania, followed by Mayotte, southern Kenya, and northern Mozambique. If biomass can be maintained, the broad distributions of species combined with compensatory community responses should maintain high diversity and ecological resilience to climate change and other human stressors.

Preliminary characterization of coral reef diversity using environmental DNA in a hyper-diverse context

Monitoring coral reef communities remains a scientific cornerstone of marine biodiversity conservation and management. Environmental DNA (eDNA) has recently emerged as a passive detection tool to enumerate organisms in dynamic marine systems. The utility of eDNA to provide meaningful results for coral reef conservation and management in Indonesia, a hyper-diverse and data-limited tropical area, however, remains poorly understood. In this study, we conducted seawater and sediment eDNA surveys in three regions of Indonesia and amplified them using a general metazoan primer. We found that eDNA revealed a diverse array of reef organisms overall (>11,000 amplicon sequence variants, or ASVs), including species of management importance (i.e., sharks and mollusks) that are otherwise missed by conventional surveying methods. Most fish and coral eDNA detections were verified by our concurrent visual surveys of those taxonomic groups, demonstrating the utility of these two methods as complementary approaches for broad-scale reef bioassessment. Almost half of the ASVs, however, were unclassified Eukaryotes. We estimated that with our eDNA protocol, 119–197 water samples and 259–375 sediment samples would be needed to recover the complete suite of operational taxonomic units (a genetic proxy for species) in each region. Despite not reaching the full saturation of potential diversity or taxonomic detection within regions, eDNA sampling revealed community compositions were regionally distinct, even though water and sediment samples differed in community structure and exhibited high heterogeneity. Our precursory examination of a taxonomically-broad eDNA survey in Indonesia highlights the short and long-term utility of the method as a confirmatory and complementary tool for biomonitoring, research, and conservation purposes. Nonetheless, more rigorous sampling, methodological refinements, and database curation are needed for eDNA to reach its full potential in Indonesia.

Study of Coral Reefs in the Tourism Zone of Hoga Island, Wakatobi National Park, Southeast Sulawesi, Indonesia

One of the ecosystems in tropical waters is the coral reef. Coral reefs serve multiple functions, both ecologically and economically. The marine waters in Wakatobi Regency boast diverse coral reefs, and this study aims to assess the coral reefs in one of its regions, specifically in the waters around Hoga Island, part of Wakatobi National Park. The research was conducted from March to May 2023, involving direct observations at the research site. The collected data were then analyzed and presented descriptively concerning the percentage of coral reefs in the study area. The percentage of coral cover in the growth forms (lifeform) of the Wakatobi National Park tourism zone, region II, revealed that, at the first station, coral cover was 46.33%, dominated by Coral Branching (CB) at 22.36%, and Biotic, primarily Soft Coral (SC), at 14.95%. At the second station, coral cover was 36.13%, with Coral Branching (CB) accounting for 11.53%, and Soft Coral (SC) at 25.33%. The third station exhibited a coral cover percentage of 60.37%.

Reduced small-scale structural complexity on sponge-dominated areas of Indo-Pacific coral reefs

Corals provide a complex 3D framework that offers habitat to diverse coral reef fauna. However, future reefs are likely to experience reduced coral abundance. Sponges have been proposed as one potential winner on future coral reefs, but little is known of how they contribute to reef 3D structure. Given the ecological importance of structural complexity, it is critical to understand how changes in the abundance of structure-building organisms will affect the three-dimensional properties of coral reefs. To investigate the potentially important functional role of coral reef sponges as providers of structural complexity, we compared the structural complexity of coral- and sponge-dominated areas of an Indonesian coral reef, using 3D photogrammetry at a 4 m2 spatial scale. Structural complexity of 31 4 m2 quadrats was expressed as rugosity indicating reef contour complexity (R), vector dispersion indicating heterogeneity of angles between reef surfaces (1/k), and fractal dimension indicating geometrical complexity at five different spatial scales between 1 and 120 cm (D1–5). Quadrats were identified as high- or low-complexity using hierarchical clustering based on the complexity metrics. At high structural complexity, coral- and sponge-dominated quadrats were similar in terms of R and 1/k. However, smallest-scale refuge spaces (1–5 cm) were more abundant in coral-dominated quadrats, whereas larger scale refuge spaces (30–60 cm) were more abundant in sponge-dominated quadrats. Branching and massive corals contributed the most to structural complexity in coral-dominated quadrats, and barrel sponges in sponge-dominated quadrats. We show that smaller-scale refugia (1–5 cm) are reduced on sponge-dominated reefs at the spatial scale considered here (4 m2), with potential negative implications for smaller reef fauna.

Reef fish monitoring as a coral reef resilience indicator in the Sempu Strait, South of East Java, Indonesia

Abstract. Bintoro G, Isdianto A, Harahab N, Kurniawan A, Wicaksono AD, Maharditha R, Fathah AL, Putri BM, Haykal MF, Asadi MA, Setyanto A, Lelono TD, Luthfi OM, Pratiwi DC. 2023. Reef fish monitoring as a coral reef resilience indicator in the Sempu Strait, South of East Java, Indonesia. Biodiversitas 24: 4950-4959. Sempu Island is designated as a nature reserve which is surrounded by a fairly high diversity of coral reefs. Since the high activities of fishing ports near this island, the anthropogenic pressure seriously became a threat to the biodiversity of coral reefs in this nature reserve. Continuous observation of reef fish is an important activity to monitor the coral reef health condition. Since then, bimonthly monitoring using an underwater visual census has been conducted from October 2021 to May 2022. Based on these observations obtained that the average reef fish abundance was in the "low" category, namely 0.516 ind/m2 in October 2021, 0.527 ind/m2 in December 2021, 0.522 ind/m2 in February 2022, and 0.378 ind/m2 in May 2022. The abundance of reef fish obtained consisted of three categories: indicators, targets, and majors. Overall, the Pomacantridae family, from the major fish category, has the largest abundance compared to other families. While the range of coral coverage was 6-21.3%, which was included in the "bad" category. There was a relationship with a value of 0.462 (medium) between coral cover and fish abundance. The abundance of reef fish at 21.4% was influenced by coral cover, while the remaining 78.6% was influenced by other factors outside of the tested variables. The decline in reef fish abundance in 2015-2022 can be caused by a decrease in coral cover in the Sempu Strait.

Ecological vulnerability assessment of coral islands and reefs in the South China Sea based on remote sensing and reanalysis data

Coral reefs are ecosystems that are highly vulnerable to external environmental impacts, including changes associated with ocean acidification and global warming. Assessing the vulnerability of coral reef growth environments over large areas of the sea is a difficult and complex process, as it is influenced by many variables. There are few studies on environmental vulnerability assessment of coral islands and reefs in the South China Sea. It is therefore particularly important to understand the environmental sensitivity of corals and how coral communities respond to changes in climate-related environmental variables. In this study, indicators were selected mainly from natural environmental factors that hinder the development of coral reefs. The sea surface temperature (SST), sea surface salinity (SSS), wind velocity (WV) and direction, sea level height (SL), ocean currents (OC), and chlorophyll concentration (Chl) of coral reefs in South China Sea Island were integrated to calculate the coral reef environmental vulnerability region. In a GIS environment, Spatial Principal Component Analysis (SPCA) was used to develop sensitivity models and evaluate the ecological vulnerability of coral reefs. Based on the Environmental vulnerability indicator (EVI) values, the study area was classified as 5 grades of ecological vulnerability: Potential (0.000–0.577), Light (0.577–0.780), Medium (0.780–0.886), Heavy (0.886–0.993) and Very Heavy (0.993–1.131). Sensitivity models identified regional gradients of environmental stress and found that some coral reefs in western Malaysia and southwestern Philippines have higher vulnerability. Meanwhile, the study found that the reefs of Paracel Islands and Macclesfield Bank areas of medium vulnerability. Future use of high-precision data from long time series will allow better estimates of site-specific vulnerability and allow for the precise establishment of marine protected areas so that the ecological diversity of coral reefs can be sustained.

Local heterogeneity of coral reef diversity and environmental stress provides opportunities for small‐scale conservation

AbstractAimStrong social‐ecological trade‐offs between resource extraction and protection have created challenges for large, protected area management in natural resource‐dependent countries. Therefore, local governments and community conservation activities are becoming common and information about low environmental exposure and high biodiversity can provide for planning localized conservation activities.LocationThe western Indian Ocean.MethodsCoral reef sites were evaluated for local‐scale environmental and species richness to elucidate local patterns in spatial heterogeneity. Local coral and fish taxonomic richness and coral community susceptibility to stress were normalized to partially account for common and heterogenous disturbances to coral cover and fish biomass. Residuals of these three response variables were evaluated for local geographic patterns and specific relationships with 21 environmental variables using machine learning methods.ResultsRichness was highly variable at local geographies and had a double‐peaked shape with latitudes. Thirteen of the 21 examined variables were selected and indicated complex, spatially heterogeneous and weak cumulative predictive relationships with specific environmental and human influences. For example, each selected variable contributed 7% to 25% of the variance but with different relationships for the three responses. Coral fish richness and coral community susceptibility correlations were positive but weak and therefore produced different local spatial patterns. Nevertheless, these spatial patterns exhibited some coarse‐scale similarities indicating locations with shared positive community attributes and potential climate refugia. Shared richness variables included depth and wave energy, temperature variables of SST skewness, excess heat and rate of rise. Human influences of distance to shore, human populations and cities were also selected for richness and community susceptibility responses.Main ConclusionsPlanning to include local stress and richness patterns variability could contribute to species persistence. From these specific data, sites in the Pemba Channel between the Tanzanian mainland and Pemba Island, and northern Mozambique and Madagascar fit refugia characteristics.

Diversity of Coral Reefs at Insrom Beach, Biak Numfor Regency

Diversity of Coral Reefs at Insrom Beach, Biak Numfor Regency

Discovery of habitat preferences and community structure of Echinoderms in Kri, Raja Ampat, Indonesia

Abstract. Siburian RHS, Tapilatu JR, Tapilatu ME. 2023. Discovery of habitat preferences and community structure of Echinoderms in Kri, Raja Ampat, Indonesia. Biodiversitas 24: 3968-3976. Raja Ampat, located in Papua, Indonesia, is home to one of the most diverse coral reef ecosystems and is a component of the Coral Triangle. The coral in Raja Ampat is still considered to be in good health. Although the marine fauna in Raja Ampat is pristine and diverse, there have still only been a few studies in this region. The scientific research on the Echinoderms in Raja Ampat is limited, particularly as a primary input for data research. In this study, we present Echinoderm's habitat and community structure in the Kri coastal area at Mansuar Island based on the data collected at field sampling. From January to February 2023, data were collected intensively during morning and afternoon low tide for three repetitions each, at 5-10 m depths. We conducted morphological species identification. Asteroidea, Holothuroidea, Echinoidea, and Crinoidea were found to be the four major classes of Echinodermata that dominated the sampling area, with a total of 20 species and 180 individuals. Each Echinodermata species has its preferred Kri coastal habitat based on its food supply, unique behavior, and body structure. In addition, the result indicates that this region has a moderate diversity level, with low dominance and moderate to high uniformity. This research provides new information on the ecology of Echinoderms in eastern Indonesia, particularly in Raja Ampat.

Molecular mapping of coral reef diversity

Molecular mapping of coral reef diversity

Lessons learned implementing mineral accretion and coral gardening at Agincourt Reef, Great Barrier Reef

SummaryThe health and diversity of coral reefs are critically important to the stability and value of the marine tourism industry. Declines in coral reef health through climate change impacts and cyclones, and associated media coverage, have impacted tourism visitation. In January 2018, a major change in Australian Government policy included a Reef Restoration and Adaptation Program to investigate the best science and technology options for helping the Great Barrier Reef recover and adapt to the changing environment. We report on a trial of two intervention methods, mineral accretion and coral gardening, to improve hard coral recovery at a popular site on the Great Barrier Reef. We installed six artificial reef substrates onto which an equal number of coral fragments of seven species were transplanted over the course of two years. During this time, three of the six treatments were connected to a low‐voltage power source to encourage mineral accretion and enhance coral growth. Electrolysis resulted in substantial mineral accretion on the steel substrate, however, the technology had no positive effect on the survival or growth of transplanted coral colonies. After 13 months, a second round of transplanted coral fragments was undertaken, and the electrolysis was discontinued. Over a four‐year period, mean live coral cover increased significantly in both treatment locations, from 1.7% and 0% to 80.8% and 75.8%, respectively. Control locations increased insignificantly from a mean of 5% to 14.2%. The mineral accretion technology proved technically challenging and did not support the growth or health of transplanted corals, providing no evidence to support the use of mineral accretion technology for this purpose. The technology may, however, have applications in the creation of new, solid substrates and for initial rubble stabilisation efforts. These results demonstrate the effective use of artificial substrates in conjunction with coral gardening techniques for the recovery of hard coral at degraded tourism sites.

Differing Responses of Three Scleractinian Corals from Phuket Coast in the Andaman Sea to Experimental Warming and Hypoxia

An unprecedented decline in the diversity and health of coral reefs is occurring around the world as they are threatened by multiple global and local stressors. Rising seawater temperature and low dissolved oxygen (DO) conditions are expected to intensify as a result of climate change. Understanding the responses of corals to these stressors is necessary for making predictions and devising mitigation strategies. The three coral species—Porites lutea, Montipora tuberculosa, and Pocillopora verrucosa—were sampled from Patong Bay, Phuket, Thailand, as representatives of different coral morphologies. Coral nubbins were subjected to experimental investigation under ambient conditions (29 °C, DO > 6 mgL−1), heat stress (32 °C), hypoxia (DO < 2 mgL−1), and heat stress + hypoxia treatments. Photosynthetic performance indicators Fv/Fm and Fv/F0 and physiological parameters Symbiodiniaceae density, pigment concentration, and growth rate were quantified. We found P. verrucosa (branching) to be the most sensitive and severely affected by heat stress or hypoxia, more so than P. lutea (massive) and M. tuberculosa (tabular). The combination of these stressors had less impact on these species, except for a decline in growth rate of M. tuberculosa. This study also suggests that the corals respond differently to high temperature and low oxygen, with their sensitivity depending on species. These responses, however, may differ according to the lighting, especially in hypoxic conditions. The results fill a research gap to help predict the vulnerability of these three coral species in shallow reef habitats under climate change scenarios.

Intake of trace contaminants by corals in Abrolhos reef bank (western South Atlantic) during two decades of coastal impacts

Abrolhos is the largest and most diverse coral reef system in the South Atlantic. It is home to several endemic coral species and a site of cetaceous reproduction. Like any other reef ecosystem worldwide, it experiences multiple disturbances associated with increasing sea surface temperatures, El Niño events, and, most recently, oil spill pollution. In addition to these global stressors, the Abrolhos region may have been impacted by coastal human interventions, a large-scale mining disaster, floods, and extra-tropical cyclones that affected the region during the last 20 years. Among these stressors, the Fundão dam collapse (the largest in the Southern Hemisphere) deserves special attention since it delivered significant amounts of iron tailings to the nearby coast. To investigate the region's recent history, we collected, dated, and performed detailed geochemical and isotopic analyses on two coral colonies (i.e., Siderastrea stellata and Mussismilia harttii), in order to determine if effects of recent human activity on reef systems (and most recent natural impacts) could be detected thorough bioaccumulation of metals in their skeletons. In this context, we detected an abrupt increase in Fe and Mn concentrations in the coral skeleton, which are among the main constituents of the Fundão dam tailings. We show that a concomitant increase in metal concentrations tracks contaminant dispersion of the Fundão dam tailings released to the western South Atlantic. Besides this event, our data also show that coastal dredging activities in the nearby coral reef site (i.e., at the Tomba channel) and two natural episodes (i.e., the flood of 2013 and the anomalous extra-tropical cyclonic activity in 2008) were also recorded in the coral skeleton based on changes in Rare Earth Elements distribution, Rb and U concentrations.