Coral Biodiversity Research Articles

Conservation priorities for reef-building coral biodiversity across multiple dimensions in the South China Sea

Conservation priorities for reef-building coral biodiversity across multiple dimensions in the South China Sea

Loss of Coral Trait Diversity and Impacts on Reef Fish Assemblages on Recovering Reefs.

Understanding patterns of biodiversity change is essential as coral reefs experience recurrent cycles of disturbance and recovery. Shifts in the total cover and species composition of habitat-forming corals can have far-reaching consequences, including shifts in coral functional traits and impacts on local fish assemblages. We surveyed coral and fish assemblages along the southern coast of Hainan Island near Sanya, China, in 2006, 2010, and 2018, during a period with repeated mass bleaching events. We showed that coral biodiversity in this region is in a state of flux, with losses and gains in coral cover and an increase in species richness over time. Despite increasing species diversity, the region suffered a loss of coral trait diversity by 2010, with an incomplete recovery by 2018, owing to declines in species with key habitat-forming traits (e.g., high surface areas and fractal structure) such as corymbose corals. Concurrently, there was an increase in functional redundancy due to the proliferation of the dominant encrusting and massive corals. Coral cover was positively associated with the abundance of reef fish, indicating that the changes observed in coral abundance can impact reef-associated species. These results demonstrate that the slow recovery of coral biodiversity in southern Hainan Island has been hampered by the loss of specific coral traits and highlight the importance of protecting vulnerable coral traits in conservation and management strategies.

Dancing Towards the End—Ecological Oscillations in Mediterranean Coral Reefs Prior to the Messinian Salinity Crisis (Calcare di Rosignano Formation, Acquabona, Tuscany, Italy)

The lower Messinian Calcare di Rosignano Formation (Tuscany, Italy, 43° N) preserves one of the youngest and northernmost examples of coral reefs in the Mediterranean. The outcropping succession of the Acquabona quarry consists of four main facies, namely, in ascending stratigraphic order: (1) coral boundstone, (2) coralline algal rudstone, (3) serpulid floatstone to packstone, and (4) peloidal packstone to grainstone. The succession displays a trend toward increasingly more shallow conditions and progressively more restricted water circulation. The coral reef displays a limited coral biodiversity and a remarkable abundance of heterotrophs, similar to modern coral reefs developed at the edges of the ecological niche of symbiont-bearing colonial corals. The widespread presence of coral colonies pervasively encrusted by coralline algae and benthic foraminifera suggests that short-term environmental perturbations caused temporary shutdowns of the coral-dominated carbonate factory. Moving upwards, there are fewer corals and more highly adaptable carbonate producers like coralline algae and serpulids. This suggests that the decline of corals had been caused by the conditions in the basin becoming more stressful, up to the collapse of the coral community. The overall succession indicates that coral-dominated ecosystems located at the edges of the coral zone are very sensitive; they can be affected even by minor perturbations and easily collapse if negative conditions persist.

Coral reef potential connectivity in the southwest Indian Ocean

The tropical southwest Indian Ocean is a coral biodiversity hotspot, with remote reefs physically connected by larval dispersal through eddies and a complex set of equatorial and boundary currents. Based on multidecadal, 2 km resolution hydrodynamic and larval dispersal models that incorporate temporal variability in dispersal, we find that powerful zonal currents, current bifurcations, and geographic isolation act as leaky dispersal barriers, partitioning the southwest Indian Ocean into clusters of reefs that tend to consistently retain larvae, and therefore gene flow, over many generations. Whilst exceptionally remote, the Chagos Archipelago can broadcast (and receive) considerable numbers of larvae to (and from) reefs across the wider southwest Indian Ocean, most significantly exchanging larvae with the Inner Islands of Seychelles, but also the Mozambique Channel region. Considering multi-generational dispersal indicates that most coral populations in the southwest Indian Ocean are physically connected within a few hundred steps of dispersal. These results suggest that regional biogeography and population structure can be largely attributed to geologically recent patterns of larval dispersal, although some notable discrepancies indicate that palaeogeography and environmental suitability also play an important role. The model output and connectivity matrices are available in full and will provide useful physical context to regional biogeography and connectivity studies, as well as supporting marine spatial planning efforts.

Assess the level of damage to the coral reef ecosystem based on substrate coverage on Bira Island, Kepulauan Seribu, Indonesia

Abstract. Komala R, Noer MI, Miarsyah M, Widyartini DS, Handayani. 2024. Assess the level of damage to the coral reef ecosystem based on substrate coverage on Bira Island, Kepulauan Seribu, Indonesia. Biodiversitas 25: 971-977. Coral reefs are coastal ecosystems that have an important ecological and economic role. Environmental pressures cause damage to ecosystems and decrease coral biodiversity. This study aims to analyze the level of damage to coral reef ecosystems based on substrate cover and obtain the latest information on coral reef ecosystem resources. The study employs a descriptive method with a survey design, utilizing Underwater Photo Transect (UPT) sampling at various depths along the coastline. The data is analyzed using Coral Point Count with Excel extension (CPCe) for substrate cover percentage and the Shannon-Wienner index for coral diversity. The findings reveal nine categories of basic substrate cover, with living hard corals constituting 32.51%, indicating a fairly damaged state. Coral resources are identified across 53 genera and 15 families, exhibiting medium diversity across stations and depths. The study highlights the need to monitor environmental threats that could further damage coral reefs and decrease diversity. The coral reef ecosystem in Bira Island is in a relatively damaged condition, with a decline in coral biodiversity, indicating an imbalance in the ecosystem. Several recommended steps include implementing coral restoration programs, monitoring coral growth, establishing critical coral habitat protection zones, and conducting conservation efforts.

Ecosystem restoration: Healing blasts from the past

Blast fishing reduces coral reefs to fields of rubble. A new study of a project to restore blast-fished reefs reveals rapid recovery of reef carbonate budgets and reef health but highlights that further work is needed to restore coral biodiversity.

Biodiversity and biogeography of zooxanthellate corals in Australasia revisited based on new data from the Kimberley

Biodiversity and biogeography of zooxanthellate corals in Australasia revisited based on new data from the Kimberley

Loss of Coral Reefs due to Ship Grounding in Indonesian Water: Case Study on Karimun Jawa National Park (TNKj)

A ship grounding on coral reefs can cause severe physical and biological damage, including coral dislodgement and removal, skeleton destruction, sediment erosion, and loss of three-dimensional complexity. The event of a ship grounding in Karimunjawa National Park caused live coral degradation of 100% and massive damage to foliose and branched coral. The total loss of hard coral biodiversity reached 261,274 colonies in an area of ±2687.87 square meters. This destruction has reduced the biodiversity of coral reefs, necessitating urgent conservation and restoration efforts in the affected area. The specific data provided, such as variations in population and density, helps provide a comprehensive understanding of the ecological damage caused by the ship grounding.

Hai loài san hô mềm Xenia novaebritanniae Ashworth, 1900 và Xenia lillieae Roxas, 1933 (Malacalcyonacea: Xeniidae) mới phát hiện ở đảo Song Tử Tây – quần đảo Trường Sa – Việt Nam

The coral in the Truong Sa archipelago (Spratly Islands) is considered of high diversity, the pervious research showed that Truong Sa archipelago has over 333 species of 71 genera and 15 families of hard corals, accounting for 74% of the species known in Vietnam and 57.6% of the coral species recorded in neighbouring South China Sea (Bien Dong) countries. However, the studying on soft coral biodiversity is extremely limited, this result was the first time two soft coral species, Xenia novaebritanniae and Xenia lillieae, were found in Spratly archipelago (Song Tu Tay/Southwest Cay). The morphological differences and sclerite structure of the soft coral specimens are described in detail. Previously, these two species were only found in the coastal waters of Central Viet Nam. Our findings not only contribute to expanding the distribution of soft corals, but also increasing the value of coral reef ecosystem biodiversity in this area.

Disturbance-Induced Changes in Population Size Structure Promote Coral Biodiversity.

AbstractReef-building coral assemblages are typically species rich, yet the processes maintaining high biodiversity remain poorly understood. Disturbance has long been thought to promote coral species coexistence by reducing the strength of competition (i.e., the intermediate disturbance hypothesis [IDH]). However, such disturbance-induced effects are insufficient to inhibit competitive exclusion. Nevertheless, there are other mechanisms by which disturbance and, more generally, environmental variation can favor coexistence. Here, we develop a size-structured, stochastic coral competition model calibrated with field data from two common colony morphologies to investigate the effects of hydrodynamic disturbance on community dynamics. We show that fluctuations in wave action can promote coral species coexistence but that this occurs via interspecific differences in size-dependent mortality rather than solely via stochastic fluctuations in competition (i.e., free space availability). While this mechanism differs from that originally envisioned in the IDH, it is nonetheless a mechanism by which intermediate levels of disturbance do promote coexistence. Given the sensitivity of coexistence to disturbance frequency and intensity, anthropogenic changes in disturbance regimes are likely to affect coral assemblages in ways that are not predictable from single-population models.

A Global-Scale Ecological Niche Modeling of the Emerging Pathogen Serratia marcescens to Aid in its Spatial Ecology.

Serratia marcescensis a big emerging concern for human health and coral biodiversity. Spatial ecology and the influencing factors on pathogen ecology, however, remain unknown. The study forms the first global risk assessment ofS. marcescens. MaxEnt niche modeling was applied using two biotic and sixteen abiotic variables. The world was classified into five risk-level categories based on the pathogen ecology, and the world population exposed toS. marcescensinfection was then quantified. The prepared model showed an area under the curve value of 0.918 ± 0.028, implying excellent prediction ability. The highly and moderately suitable areas occupied around 0.52% and 17.9% of the total global land area. The order of probability of havingS. marcescens-related infections was Asia > North America > South America > Europe > Africa > Australia. Human population density and temperature were the most influential factors in the distribution. The moderate to high transmission risk zones contained 0.20% (1.61 billion people) of the human population. In brief, these results give novel insights into its spatial ecology and provide the risk maps that can be utilized to plan targeted strategic control measures against future invasions of this emerging pathogen.

The abundance of coral diseases and compromise health in marine protected areas on Dampier waters, Raja Ampat

The extent of coral reefs, coral biodiversity, and associated biota are known as high mega biodiversity in Indonesian waters, in other words, The Coral Triangle. Threats of coral damage have also been widely reported, including deaths due to natural factors. Coral disease is a natural factor that is not widely known for its existence around Indonesian waters. This study was conducted to obtain the abundance of coral disease by using a belt transect method of 20 m long with a width of 50 cm to the left and right of the transect line, then carried out three replications at ten observation stations in Dampier waters, Raja Ampat. The study obtained data on the abundance of coral diseases that infect eight coral genera ranging from 0-23 col/60 m2, the highest station at station 8 (23 col/60 m2). There were six types of coral disease found in the Dampier Strait MPA, including WS, BrBD, FB, AtN, Bleaching, and Tumor. The highest abundance was found in WS disease (65 col/60m2). Coral health confounding factors were found in 336 colonies with abundance at different stations ranging from 14 – 97 col/60 m2. The highest abundance was found at station 5 (97 col/60 m2), a high stressor due to being located at sub-zona Sasi and traditional use. The existence of the disease is not classified as an outbreak. However, it is necessary to be careful if there is an increase in the number of new infection cases in the exact location or other places in Indonesia.

An environmental DNA metabarcoding approach versus a visual survey for reefs of Koh Pha‐ngan in Thailand

AbstractInformation on diversity indices and abundance of individual species is crucial for the assessment of ecosystem health, especially for endangered ecosystems as coral reefs. The application of environmental DNA (eDNA) to monitor coral biodiversity is, however, just beginning to come into focus for marine biologists. In this study, an eDNA metabarcoding approach of seawater samples in three different reefs on Koh Pha‐ngan, Thailand, was compared with simultaneously collected visual census data. In addition, differences in read abundance and number of genera detected between daytime and nighttime eDNA samples were examined, and a local coral barcode reference database (n = 23 genera; COI gene) was constructed to improve assignment of eDNA reads to the genus level. As a technical extension of existing assays, two methods for library construction were compared: a commercial kit and in‐house developed fusion primers. Combining eDNA metabarcoding and visual data, 29 different genera of scleractinian corals from 14 families were detected. In addition, a log‐linear correlation was found between the abundance of eDNA reads and visually determined relative coral cover at the genus level, suggesting a predictive relationship between eDNA reads and coral cover. Results also showed diurnal variation between day and night samples in the number of eDNA reads, purported to relate to the activity phases of corals. The use of uniquely labeled fusion primers, gave comparable results to a commercially available library preparation kit. Especially with frequent use, fusion primers can be very cost‐effective, and therefore a consideration for large‐scale studies. Using a custom reference database of 89 sequences from coral tissue samples of 23 different coral genera produced better results than querying against NCBI GenBank, highlighting the importance of locally optimized databases. We consider these results important for establishing eDNA as a complementary tool to visual surveys to track changes in coral diversity and cover.

Initiating a DNA Barcoding Reference Library of Stony Corals from the Gulf of Eilat (Red Sea)

Accurate identification of scleractinian coral species is fundamental for proper biodiversity estimates, for aiding in efforts of reef monitoring, conservation, restoration, and for the management of coral reefs. Here, we provide the first DNA barcoding reference library for coral species in Eilat, Red Sea, based on the mitochondrial gene cytochrome c oxidase subunit I (COI), targeting the identification of stony coral species from shallow (0–12 m) reefs. A total of 191 specimens were collected, depicting 14 families, 39 genera, and 94 species (all are new full species records to the BOLD system). Three species (Sclerophyllia margariticola, Cyphastrea magna, and Psammocora profundacella) are first records for Eilat’s coral reef. The results presented here strengthen the claim that COI is not universally informative for delimitation of stony coral species, a notion reinforced by the constructed maximum likelihood phylogenetic tree. This library is the first step in a long journey towards elucidating coral biodiversity in the coral reef at Eilat and for improving future management and monitoring efforts.

Photosynthetic usable energy explains vertical patterns of biodiversity in zooxanthellate corals

The biodiversity in coral reef ecosystems is distributed heterogeneously across spatial and temporal scales, being commonly influenced by biogeographic factors, habitat area and disturbance frequency. A potential association between gradients of usable energy and biodiversity patterns has received little empirical support in these ecosystems. Here, we analyzed the productivity and biodiversity variation over depth gradients in symbiotic coral communities, whose members rely on the energy translocated by photosynthetic algal symbionts (zooxanthellae). Using a mechanistic model we explored the association between the depth-dependent variation in photosynthetic usable energy to corals and gradients of species diversity, comparing reefs with contrasting water clarity and biodiversity patterns across global hotspots of marine biodiversity. The productivity-biodiversity model explained between 64 and 95% of the depth-related variation in coral species richness, indicating that much of the variation in species richness with depth is driven by changes in the fractional contribution of photosynthetically fixed energy by the zooxanthellae. These results suggest a fundamental role of solar energy availability and photosynthetic production in explaining global-scale patterns of coral biodiversity and community structure along depth gradients. Accordingly, the maintenance of water optical quality in coral reefs is fundamental to protect coral biodiversity and prevent reef degradation.

Fast-growing species shape the evolution of reef corals

Ecological interactions are ubiquitous on tropical coral reefs, where sessile organisms coexist in limited space. Within these high-diversity systems, reef-building scleractinian corals form an intricate interaction network. The role of biotic interactions among reef corals is well established on ecological timescales. However, its potential effect on macroevolutionary patterns remains unclear. By analysing the rich fossil record of Scleractinia, we show that reef coral biodiversity experienced marked evolutionary rate shifts in the last 3 million years, possibly driven by biotic interactions. Our models suggest that there was an overwhelming effect of staghorn corals (family Acroporidae) on the fossil diversity trajectories of other coral groups. Staghorn corals showed an unparalleled spike in diversification during the Pleistocene. But surprisingly, their expansion was linked with increases in both extinction and speciation rates in other coral families, driving a nine-fold increase in lineage turnover. These results reveal a double-edged effect of diversity dependency on reef evolution. Given their fast growth, staghorn corals may have increased extinction rates via competitive interactions, while promoting speciation through their role as ecosystem engineers. This suggests that recent widespread human-mediated reductions in staghorn coral cover, may be disrupting the key macroevolutionary processes that established modern coral reef ecosystems.

Geomorphically controlled coral distribution in degraded shallow reefs of the Western Caribbean.

The development of coral reefs results from the interaction between ecological and geological processes in space and time. Their difference in scale, however, makes it difficult to detect the impact of ecological changes on geological reef development. The decline of coral cover over the last 50 years, for example, has dramatically impaired the function of ecological processes on reefs. Yet given the limited-resolution of their Holocene record, it is uncertain how this will impact accretion and structural integrity over longer timescales. In addition, reports of this ecological decline have focused on intrinsic parameters such as coral cover and colony size at the expense of extrinsic ones such as geomorphic and environmental variables. Despite these problems, several attempts have been made to predict the long-term accretion status of reefs based entirely on the contemporary health status of benthic communities. Here we explore how this ecological decline is represented within the reef geomorphic structure, which represents the long-term expression of reef development. Using a detailed geomorphic zonation scheme, we analyze the distribution and biodiversity of reef-building corals in fringing-reef systems of the Mesoamerican Reef tract. We find a depth-related pattern in community structure which shows that the relative species distribution between geomorphic zones is statistically different. Despite these differences, contemporary coral assemblages in all zones are dominated by the same group of pioneer generalist species. These findings imply that first, coral species distribution is still controlled by extrinsic processes that generate the geomorphic zonation; second, that coral biodiversity still reflects species zonation patterns reported by early studies; and third that dominance of pioneer species implies that modern coral assemblages are in a prolonged post-disturbance adjustment stage. In conclusion, any accurate assessment of the future viability of reefs requires a consideration of the geomorphic context or risks miscalculating the impact of ecological changes on long-term reef development.

CORAL BIODIVERSITY IN PULAU MIANG, EAST KALIMANTAN, INDONESIA

This study aims to discover the potential of resources and diversity of hard corals of Pulau Miang island (118°0'20"E, 0°44’0"N) located in Sangkulirang District, East Kutai Regency, East Kalimantan. This island is also called Pulau Miang Besar by locals to distinguish it from an uninhabited island to the northeast from this island. The coral reef in Pulau Miang has formed a fringing natural barrier protecting the island from erosion. Pulau Miang is part of the world’s coral triangle region, with very high coral diversity. Since this island is a remote area, very little literature related to its coral biodiversity, and this study became the first article that revealed this coral reef ecosystem. Quadrat transects were used to calculate the percentage of coral life covering this island. Transects lay down 100 times at two different depths and were photographed to measure the coral area within transects. An ImageJ software was used to count and mark coral colonies. The result showed that the average percentage of coral cover area in Pulau Miang was 21.39%, categorized as poor condition, while the coral biodiversity index was 1.98 or in an intermediate state. Two genera dominated coral taxa – Acropora and Porites. Based on the number of colonies and coral cover area, Acropora and Porites are the dominant coral genera in Pulau Miang among coral taxa.

Regional-scale genetic differentiation of the stony coral Desmophyllum dianthus in the southwest Pacific Ocean is consistent with regional-scale physico-chemical oceanography

Deep-sea corals are diverse and abundant in New Zealand’s EEZ and the southwest Pacific Ocean. We assessed genetic diversity and gene flow of the deep-sea scleractinian (stony cup coral) Desmophyllum dianthus in five areas (Kermadec Ridge, Louisville Seamount Chain, Chatham Rise, Campbell Plateau, Macquarie Ridge), and applied dispersal kernels estimated from drifters observations and seascape genetics to compare with observed connectivity patterns and regional physico-chemical data. We observed pronounced between-region genetic differentiation, high levels of self-recruitment, but also high connectivity between distant sites (e.g., at the Kermadec Ridge inside the New Zealand EEZ, and the Louisville Seamount Chain outside the New Zealand EEZ). Genetic diversity was marginally highest at the Kermadec Ridge, whilst populations on the Chatham Rise showed evidence of unique genetic diversity that may be driven by converging ocean currents. Overall, patterns of genetic connectivity were consistent with oceanographic predictions of dispersal routes. Seascape genetic analyses indicated that environmental variables most often related to physical seafloor habitat characteristics were important predictors of regional-scale genetic differentiation of D. dianthus. Our research shows that current spatial closures within the New Zealand EEZ and surrounding high seas areas do not encompass the extent of genetic diversity and connectivity for D. dianthus, which parallels research for other deep-sea taxa in the region. Future measures implemented to protect deep-sea coral biodiversity require consideration of complex connectivity patterns and migration routes amongst taxa, at various spatial scales. This study demonstrates that a combined gene flow, seascape genetics and dispersal kernel modelling approach can provide a robust evaluation of connectivity in deep-sea environments to inform management decision making at the scale of the southwest Pacific Ocean.

Are Sunken Warships Biodiversity Havens for Corals?

Coral reefs are threatened by climate change, overfishing, and pollution. Artificial reefs may provide havens for corals, both to escape warming surface waters and to assist in the geographic migration of corals to more habitable natural reef conditions of the future. The largest artificial reefs have been generated by nearly 2000 shipwrecks around the world, but the coral diversity on these wrecks is virtually unknown. Ship size and hull material, location relative to natural reef, time since sinking, ocean currents, and water depth may affect coral diversity. As a test of the biodiversity capacity of very large sunken structures relative to surrounding natural reef, we carried out technical diver-based surveys to quantify genus-level coral diversity on 29 warships sunk in Bikini Atoll and Chuuk Lagoon. We also assessed whether ship length, as an index of substrate availability, and water depth, as an indicator of light and temperature, can serve as predictors of coral diversity. We surveyed a total of 9105 scleractinian corals. The total number of genera identified at Bikini was 34, and at Chuuk it was 51, representing 67% and 72% of genera found on natural reefs at Bikini and Chuuk, respectively. Ship length, but not water depth, was positively correlated with relative abundance and richness at the genus level. Our results suggest that very large wrecks can serve as havens for reef-building corals with a broad genetic diversity, expressed at the genus level, commensurate with corals found on neighboring natural reefs. The role of large artificial reefs could include protecting coral biodiversity from warming surface waters.