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Metal stable isotopes in marine carbonates have been widely used as novel proxies for metal cycling through the geological past. Amongst these metals, copper (Cu) and zinc (Zn) have received great attention owing to their vital roles in metabolic processes. However, whether modern marine biogenic carbonates record the seawater isotope signatures of Cu (δ65Cu) and Zn (δ66Zn) and mechanisms and factors controlling isotope fractionation of these metals remain unclear, hindering applications of both isotope systems in paleoceanography. Here we present annually-resolved records of δ65Cu and δ66Zn in seven coral (Porites) cores sampled from different marine settings in the South China Sea and the Luzon Strait, western Pacific. We find that the aragonitic skeletons of corals are enriched in light Cu but heavy Zn isotopes relative to surface seawaters, with δ65Cu and δ66Zn in the range of −0.16 ± 0.06‰ to 0.40 ± 0.05‰ and 0.06 ± 0.04‰ to 0.46 ± 0.08‰ (2SD), respectively. The coral δ65Cu exhibits significant inter- and intra-colony variations, which are most likely controlled by Rayleigh-type fractionation in the calcifying fluids of corals rather than by changes in environmental factors or seawater δ65Cu. We thus suggest that δ65Cu in ancient carbonates may not be a direct record of Cu isotope compositions in coeval seawaters. In contrast, coral δ66Zn shows insignificant temporal variation, and the Zn isotope fractionation between individual corals and seawaters are relatively small and constant (0.10 ± 0.05‰, n = 33, 2SD). This limited Zn isotope fractionation is much lower than that determined during inorganic precipitation of calcite, which is likely due to pH up-regulation by the coral that changes aqueous Zn speciation, and preferential organic complexation of the heavy Zn isotopes in the calcifying fluids. Therefore, Porites corals are promising archives for tracking historical changes of surface seawater δ66Zn. Our new datasets of reef carbonates, particularly the coral δ65Cu values which are measured for the first time, could provide a better constrain on marine Cu and Zn geochemistry and their modern oceanic mass and isotope budgets.

Coral cover and community structure in the Arabian Gulf have changed considerably in recent decades. Recurrent bleaching events have dramatically reduced the abundance of previously dominant Acropora corals and have given space to other more thermally resistant coral taxa. The loss of Acropora spp. has reduced reef structural complexity and associated biodiversity. Sir Bu Nair Island (SBN) is a nature reserve in the United Arab Emirates that sustains some of the last dense and extensive Acropora stands in the southern Gulf. This study investigated coral recruitment at a southern coral reef on SBN and examined larval dispersal and reef connectivity between SBN and other local and regional reefs through an agent-based model coupled with a 3D hydrodynamic model. Recruitment was surveyed with settlement tiles deployed from April to September 2019. Contrary to other reefs in the Gulf, we found that Acropora is indeed the major coral recruiter settling at SBN reefs, followed by Porites. The models indicate that SBN reefs are mostly self-seeding but also connected to other reefs in the Gulf. SBN can supply coral larvae to the neighbouring islands Siri and Abu Musa, and nearby reefs along with the north-eastern Emirates, Iranian coast and Strait of Hormuz. Findings highlight the importance of SBN to protect remnant populations of the locally almost extinct Acropora in a region where natural coral recovery is increasingly sparse.

This study investigates the effects of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals naturally living at CO2 seeps and adjacent control sites from two locations (Dobu and Upa Upasina) in the Papua New Guinea underwater volcanic vent system. The seeps are characterized by seawater pH values ranging from 8.0 to about 7.7. The skeletal porosity of Galaxea fascicularis, Acropora millepora, massive Porites, and Pocillopora damicornis was higher (up to ~ 40%, depending on the species) at the seep sites compared to the control sites. Pocillopora damicornis also showed a decrease of micro-density (up to ~ 7%). Thus, further investigations conducted on this species showed an increase of the volume fraction of the larger pores (up to ~ 7%), a decrease of the intraskeletal organic matrix content (up to ~ 15%), and an increase of the intraskeletal water content (up to ~ 59%) at the seep sites. The organic matrix related strain and crystallite size did not vary between seep and control sites. This multi-species study showed a common phenotypic response among different zooxanthellate corals subjected to the same environmental pressures, leading to the development of a more porous skeletal phenotype under OA.

Information about the distribution of alleles among marine populations is critical for determining patterns of genetic connectivity that are essential in modern conservation planning. To estimate population connectivity in Singapore's urbanized equatorial reef system, we analysed single nucleotide polymorphisms (SNPs) from two species of reef‐building corals with distinct life histories. For Porites sp., a broadcast‐spawning coral, we found cryptic lineages that were differentially distributed at inshore and central‐offshore sites that could be attributed to contemporary surface current regimes. Near panmixia was observed for Pocillopora acuta with differentiation of colonies at the farthest site from mainland Singapore, a possible consequence of the brooding nature and relatively long pelagic larval duration of the species. Furthermore, analysis of recent gene flow showed that 60–80% of colonies in each population were nonmigrants, underscoring self‐recruitment as an important demographic process in this reef system. Apart from helping to enhance the management of Singapore's coral reef ecosystems, findings here pave the way for better understanding of the evolution of marine populations in South‐East Asia.

In a time of unprecedented ecological change, understanding natural biophysical relationships between reef resilience and physical drivers is of increasing importance. This study evaluates how wave forcing structures coral reef benthic community composition and recovery trajectories after the major 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. Benthic cover and substrate rugosity were quantified from digital imagery at 23 fore reef sites around a small coral atoll (Salomon) in 2020 and compared to data from a similar survey in 2006 and opportunistic surveys in intermediate years. Cluster analysis and principal component analysis show strong separation of community composition between exposed (modelled wave exposure > 1000 J m−3) and sheltered sites (−3) in 2020. This difference is driven by relatively high cover of Porites sp., other massive corals, encrusting corals, soft corals, rubble and dead table corals at sheltered sites versus high cover of pavement and sponges at exposed sites. Total coral cover and rugosity were also higher at sheltered sites. Adding data from previous years shows benthic community shifts from distinct exposure-driven assemblages and high live coral cover in 2006 towards bare pavement, dead Acropora tables and rubble after the 2015/2016 bleaching event. The subsequent recovery trajectories at sheltered and exposed sites are surprisingly parallel and lead communities towards their respective pre-bleaching communities. These results demonstrate that in the absence of human stressors, community patterns on fore reefs are strongly controlled by wave exposure, even during and after widespread coral loss from bleaching events.

To better understand the decline of one of earth’s most biodiverse habitats, coral reefs, many survey programs employ regular photographs of the benthos. An emerging challenge is the time required to annotate the large volume of digital imagery generated by these surveys. Here, we leverage existing machine-learning tools (CoralNet) and develop new fit-to-purpose programs to process and score benthic photoquadrats using five years of data from the Smithsonian MarineGEO Network’s biodiversity monitoring program at Carrie Bow Cay, Belize. Our analysis shows that scleractinian coral cover on forereef sites (at depths of 3–10 m) along our surveyed transects increased significantly from 6 to 13% during this period. More modest changes in macroalgae, turf algae, and sponge cover were also observed. Community-wide analysis confirmed a significant shift in benthic structure, and follow-up in situ surveys of coral demographics in 2019 revealed that the emerging coral communities are dominated by fast-recruiting and growing coral species belonging to the genera Agaricia and Porites. While the positive trajectory reported here is promising, Belizean reefs face persistent challenges related to overfishing and climate change. Open-source computational toolkits offer promise for increasing the efficiency of reef monitoring, and therefore our ability to assess the future of coral reefs in the face of rapid environmental change.

Reef-building corals in the genus Porites are one of the most important constituents of Indo-Pacific reefs. Many species within this genus tolerate abnormally warm water and exhibit high specificity for particular kinds of endosymbiotic dinoflagellates that cope with thermal stress better than those living in other corals. Still, during extreme ocean heating, some Porites exhibit differences in their stress tolerance. While corals have different physiological qualities, it remains unknown whether the stability and performance of these mutualisms is influenced by the physiology and genetic relatedness of their symbionts. We investigated two ubiquitous Pacific reef corals, Porites rus and Porites cylindrica, from warmer inshore and cooler offshore reef systems in Palau. While these corals harbored a similar kind of symbiont in the genus Cladocopium (within the ITS2 C15 subclade), rapidly evolving genetic markers revealed evolutionarily diverged lineages corresponding to each Porites species living in each reef habitat. Furthermore, these closely related Cladocopium lineages were differentiated by their densities in host tissues, cell volume, chlorophyll concentration, gross photosynthesis, and photoprotective pathways. When assessed using several physiological proxies, these previously undifferentiated symbionts contrasted in their tolerance to thermal stress. Symbionts within P. cylindrica were relatively unaffected by exposure to 32℃ for 14 days, whereas P. rus colonies lost substantial numbers of photochemically compromised symbionts. Heating reduced the ability of the offshore symbiont associated with P. rus to translocate carbon to the coral. By contrast, high temperatures enhanced symbiont carbon assimilation and delivery to the coral skeleton of inshore P. cylindrica. This study indicates that large physiological differences exist even among closely related symbionts, with significant implications for thermal susceptibility among reef-building Porites.

An exceptionally large coral Porites sp. has been identified and measured at Goolboodi (Orpheus Island), Great Barrier Reef (GBR). This coral was measured in March 2021 during citizen science research of coral reefs in the Palm Islands group. We conducted a literature review and consulted scientists to compare the size, age and health of the Porites with others in the GBR and internationally. This is the largest diameter Porites coral measured by scientists and the sixth highest coral measured in the GBR. The health of the Porites was assessed as very good with over 70% live coral cover and minor percentages of sponge, live coral rock and macroalgae. An estimated age of 421–438 years was calculated based on linear growth models. Manbarra Traditional Owners were consulted and suggested that the Porites be named Muga dhambi (big coral) to communicate traditional knowledge, language and culture to indigenous, tourists, scientists and students.

Oxygen isotope composition (δ18O) in Porites coral skeletons at the micrometer scale has been proposed to be uninfluenced by temperature in previous studies. Considering that temperature is the main controlling factor of coral δ18O at the macro scale, the effect of temperature on the δ18O variations at the micrometer scale should be evaluated carefully. To better understand the climatic and biological significance of high-resolution δ18O in coral skeletons, in situ δ18O values were analyzed in three modern Porites corals from the South China Sea and the Great Barrier Reef by a Cameca IMS 1280-HR secondary ion mass spectrometry (SIMS). A twice vacuum impregnation procedure for sample mount preparation and a subsection calibration method based on multiple controlling points for coral matrix effect correction were used for SIMS analysis. The derived SIMS coral δ18O time series exhibit consistent long-term variations with the monthly δ18O (measured by conventional gas isotope ratios mass spectrometry), monthly Sr/Ca, and daily sea surface temperature, first highlighting the dominant temperature control on micrometer-scale coral δ18O. The 1.5‰ fluctuation amplitude of SIMS coral δ18O at the scales of 400–800 μm can be explained by the combined SST effects of ~10-day variation and day–night fluctuation, whereas the effects of seawater δ18O and growth rate on SIMS coral δ18O seem not dominant. Some abnormally negative δ18O values possibly resulted from the primary ion bombardment on indistinguishable centers of calcification.

Degradation of inshore water quality associated with catchment modification is threatening global coral reef ecosystems. Coral trace element proxies are widely applied to document the magnitude and timing of historical changes in river runoff and other disturbances. However, conflicting interpretations of commonly used coral proxies (Ba/Ca, Y/Ca and Mn/Ca) complicate their application for examining historical changes in coastal water quality. The exploration of other coral trace element proxies (such as rare earth elements, REE) is limited in space and time, and to few coral genera. This study examined the dynamics of dissolved REE and yttrium (REEY) in the Fitzroy and Burdekin river tributaries and estuaries, Queensland, Australia. In addition, monthly-resolution long-term temporal records of Ba/Ca, Mn/Ca, Y/Ca and REEY proxies were investigated in two Porites and one Cyphastrea coral colonies from the central and southern Great Barrier Reef in order to test the reliability of these proxies to record the variability of river runoff and local anthropogenic disturbances. The results showed large scale removal of REEY (55–86%) in the low salinity mixing zones of both estuaries with significant fractionation of Nd-Yb and Y-Ho, confirming the ability of coral REEY to act as a terrestrial runoff proxy. Coralline Ba/Ca, Y/Ca and Mn/Ca records generally lack coherence with proximal discharge. However, temporal fluctuations of REEY proxies, irrespective of geographic location and coral genus, showed consistent behaviour relative to regional discharge with progressive increase of total REE/Ca and shale normalized Nd/Yb and decrease of Y/Ho during high-flow summer periods. The shifting baselines of REEY proxies in Cyphastrea grown in the turbid water setting of Rat Island effectively captured the timing of Gladstone Port dredging activities. Our findings suggest that shale normalized coral REEY distributions outperformed other commonly used trace element proxies and are robust indicators of changing inshore water quality. Longer-term records of coral REEY, even covering the period before European settlement from the 1850s, may provide a means to identify shifting baselines and evaluate and quantify the impacts of catchment alteration on coastal water quality and specific coral reef communities.

Living scleractinian corals form a narrow but often conspicuous band of marine life along tropical intertidal shores worldwide but they have generally been considered as outliers of mainstream coral communities and are thus poorly characterized. This study examined coral communities at three intertidal habitats, i.e., reef flats, sloping seawalls, and vertical seawalls, in Singapore, looking at species diversity, abundances, growth forms, and colony sizes. A total of 35 coral species were recorded, of which the majority (51%) were typically of massive growth form. Reef flats had the highest number of species (30), followed by sloping seawalls (21). Species on vertical seawalls (11) were a subset of the two other habitats. Colonies were dominantly massive (72%) and sparsely distributed with average colony densities between 0.05 and 0.4 colonies/m2. Species Porites lobata-lutea complex was widespread and most abundant, comprising 21–30% of colonies in each habitat. Six other species common across all habitats were Dipsastraea speciosa, Favites abdita, Goniastrea retiformis, Platygyra verweyi, Platygyra pini, and Platygyra sinensis. Of these, only colony sizes of G. retiformis (mean ± SE, reef flats 30 ± 4 cm, sloping seawalls 9.5 ± 1.7 cm, vertical seawalls 11.7 ± 1.4 cm) and Porites lobata-lutea complex (41.8 ± 8.3 cm, 26.8 ± 6.3 cm, 12.3 ± 1.6 cm) showed significant differences (p

It is hypothesized that spatio-temporal variability in larval supply is caused by multiple biophysical drivers which correlate with the occurrence of recruitment pulses, influencing the recovery potential of coral reefs following large-scale disturbances. Here, we used a larval dispersal model to explore coral larvae dispersal patterns under variable oceanographic conditions, densities of parental colonies, and taxon-specific biology of propagules. Model predictions were validated with observed settlement and recruitment data to test the robustness of larval dispersal modelling for forecasting the recovery potential of study reefs. The model was applied to the western Pacific archipelago of Palau for 3 yr before and after major typhoon disturbances, and simulations were run and validated for 2 major broadcast-spawning reef-building taxa:AcroporaandPorites.Investigations into the relative role of physical (currents, wind, waves) and biological (taxa, disturbance impact) parameters on overall larval supply show that low wind speeds and the intermittent occurrence of north and southwest oceanic currents contributed significantly to enhancing larval supply at the scale of the archipelago. Reduced parental colony densities on eastern reefs following disturbances did not have a major impact on predicted larval supply patterns. Relatively low larval supply to most of the disturbed eastern reefs is predicted during the most common oceanographic conditions, forecasting low recovery potential through larval recruitment. Mapping the spatio-temporal dynamics of larval supply and identifying barriers to dispersal from intact to disturbed reefs can help predict recovery patterns across reef communities.

The present study reports polychaetes that bore into limestone rocks along the east coast of the Aegean Sea (eastern Mediterranean). Rock materials were collected at two depth intervals (0-5 and 5-10 m) at 15 stations in four localities of Ildiri Bay. A total of 276 specimens belonging to 12 species and four families (Eunicidae, Spionidae, Cirratulidae and Sabellidae) were recorded. Specimens belonging to Dodecaceria and Pseudopotamilla were identified at the genus level, because they differ from described species, were few in number or were in poor condition. Dipolydora giardia is a new species to the marine fauna of Turkey. The most dominant and frequent family in the area was Eunicidae, followed by Spionidae. Lysidice ninetta and L. margaritacea comprised 59% of the total number of individuals. The number of species and individuals, and the diversity index did not change with regard to depth or locality. Two species assemblages were found in the area, mainly formed by Dipolydora and Lysidice species. The Lessepsian species, Palola valida, which is a new record for the Aegean Sea, occurred abundantly at the study sites, posing a risk of damage to limestone rocks in the Mediterranean Sea. The morphological features of the species identified at the generic level and the burrow structure of these species are presented. The burrow shapes of Palola siciliensis and P. valida were described for the first time in the present study; they constructed complicated galleries, including more than four entrances., TUBITAK [111Y141], This work was financially supported by TUBITAK (Project number: 111Y141).

Background The microbiomes of foundation (habitat-forming) species such as corals and sponges underpin the biodiversity, productivity, and stability of ecosystems. Consumers shape communities of foundation species through trophic interactions, but the role of consumers in dispersing the microbiomes of such species is rarely examined. For example, stony corals rely on a nutritional symbiosis with single-celled endosymbiotic dinoflagellates (family Symbiodiniaceae) to construct reefs. Most corals acquire Symbiodiniaceae from the environment, but the processes that make Symbiodiniaceae available for uptake are not resolved. Here, we provide the first comprehensive, reef-scale demonstration that predation by diverse coral-eating (corallivorous) fish species promotes the dispersal of Symbiodiniaceae, based on symbiont cell densities and community compositions from the feces of four obligate corallivores, three facultative corallivores, two grazer/detritivores as well as samples of reef sediment and water. Results Obligate corallivore feces are environmental hotspots of Symbiodiniaceae cells: live symbiont cell concentrations in such feces are 5–7 orders of magnitude higher than sediment and water environmental reservoirs. Symbiodiniaceae community compositions in the feces of obligate corallivores are similar to those in two locally abundant coral genera (Pocillopora and Porites), but differ from Symbiodiniaceae communities in the feces of facultative corallivores and grazer/detritivores as well as sediment and water. Combining our data on live Symbiodiniaceae cell densities in feces with in situ observations of fish, we estimate that some obligate corallivorous fish species release over 100 million Symbiodiniaceae cells per 100 m2 of reef per day. Released corallivore feces came in direct contact with coral colonies in the fore reef zone following 91% of observed egestion events, providing a potential mechanism for the transfer of live Symbiodiniaceae cells among coral colonies. Conclusions Taken together, our findings show that fish predation on corals may support the maintenance of coral cover on reefs in an unexpected way: through the dispersal of beneficial coral symbionts in corallivore feces. Few studies examine the processes that make symbionts available to foundation species, or how environmental reservoirs of such symbionts are replenished. This work sets the stage for parallel studies of consumer-mediated microbiome dispersal and assembly in other sessile, habitat-forming species.

Microplastic pollution in marine environments has increased rapidly during the last decades. These microplastic particles are transported into the coral reef environment from terrestrial origin. Recent investigations suggest that microplastic ingestion can adversely affect marine invertebrates, especially in the coral reef ecosystem. The present attempt has been carried out to identify the coral growth band impregnated microplastics from polished coral slabs and acid leached insoluble residues through microscopic examination. The impregnated microplastics have been present in the following descending order: Nylon > Polyester > Polypropylene > Polyethylene. The irregular-shaped black and red microplastic particles have been dominantly observed. The annual growth band impregnated microplastics are most probably derived from tourist activities and chiefly controlled by oceanic currents and sediment re-suspension. The maximum distribution of microplastics has been observed in the coral annual growth bands of 1964 and 2005. Clinical Trials Registration The present work is not a clinically related project. Hence clinical registration is not obtained/not required for publishing the results.

Colonies of the massive coral species, Porites lutea, located at six shallow reefs across Fiji, were cored and analysed to create a chronological growth rate record. Boosted regression tree models were used to investigate relationships between annual coral growth rates and corresponding environmental variables. An ecologically based prediction model was then created to determine expected coral growth distribution across shallow reefs in Fiji for the year 2019. Annual average growth rates for the Porites lutea colonies at coral reefs in Savusavu, Leleuvia, and Navakavu reflected typical values for the Porites genus in the Indo-Pacific. Conversely, annual average growth rates at Suva Harbour, Dennis Patch, and the Coral Coast were on the lower spectrum for the Indo-Pacific Porites genus. Porites lutea growth rates were significantly influenced by latitude, whereby growth rates decreased with increasing gradient away from the equator. Growth rates were highest in the 1940s and 1950s but declined from the 1960s onwards, with significant declines observed in more polluted sites. Growth rates in Fiji are influenced by a combination of site-specific water quality and annual average sea surface temperature, with secondary contributions from the colony’s distance to shore, chlorophyll concentration, and meteorological events such as tropical cyclones, storms, and ENSO events. Predicted coral growth distribution showed that lowest growth rates are predicted around the southern and south-eastern coast of Viti Levu, highlighting the need for better marine protection at these highly populated coastlines.

Los arrecifes de coral han sufrido una extensa degradación en las últimas décadas como resultado de perturbaciones antropogénicas y naturales. Este estudio presenta una caracterización histórica (1989-2015) de los cambios en la omposición del sustrato en formaciones coralinas en el archipiélago de San Bernardo. Adicionalmente, en el 2015 se evaluó la salud arrecifal (presencia de signos de deterioro) y se analizaron datos satelitales de temperatura. En general, la cobertura de coral mostró una tendencia estable entre 1989 y 2010. En 2013 y 2015 se registraron diferencias en el ensamblaje coralino las cuales pueden estar asociadas al incremento en la cobertura de las especies de los géneros Orbicella, Porites, Agaricia, Siderastrea y del hidrocoral Millepora complanata. Las menores coberturas observadas en 1989, 1991 y 2005 estuvieron posiblemente relacionados con eventos de mortalidades masivas de especies arrecifales por enfermedades y blanqueamiento. Se registró un comportamiento opuesto entre el sustrato abiótico y las algas, siendo este último grupo el componente dominante del sustrato desde el 2013. Espacialmente se presentaron diferentes tendencias. Las estaciones en Ceycen, Tintipán y Mangle presentaron mejores condiciones de desarrollo coralino en el tiempo, mientras que las estaciones en Cabruna y Palma, lugares más cercanos a los centros urbanos, presentaron indicios de tendencia hacia el deterioro. Adicionalmente, a partir de junio del 2015 se registraron valores de temperatura por encima del umbral de tolerancia al blanqueamiento (29,4 °C), por lo que posiblemente los corales enfrentaron un estrés térmico que causó blanqueamiento en 18 de las 19 estaciones evaluadas. Son esenciales las acciones de gestión sobre los impactos locales, acompañados de la información suministrada por los programas de monitoreo, para que los arrecifes puedan recuperarse de los impactos naturales y antropogénicos que los afectan.

An exceptionally large, hermatypic colony of Porites sp. has been identified and measured at Ta’u, American Samoa. This coral was measured in November 2019 as part of an effort to catalogue all large (≥ 2 m diameter) Porites colonies around Ta’u. Colonies exceeding 10 m in diameter were recorded on three different sides of the island with seasonally different wave exposures. The largest colony measured 8 m tall, 69 m in circumference and had a diameter of 22.4 m. To date, this is the biggest colony recorded in American Samoa, and one of the largest documented worldwide. It is currently unknown why such large corals exist around this particular island. Possible explanations include mild wave or atmospheric climates and minimal anthropogenic impacts. Physiologically, these colonies may be resistant and/or resilient to disturbances. Large, intact corals can help build past (century-scale) climatic profiles, and better understand coral persistence, particularly as coral communities worldwide are declining at rapid rates.

Growth anomalies (GAs), a tumour-like disease affecting scleractinian corals, have been reported across the major reef systems of the Indo-Pacific and wider Atlantic regions, predominantly affecting Acropora and Porites species. In 2018, GAs were observed for the first time on Isopora palifera, an important observation from the isolated Cocos (Keeling) Islands in the East Indian Ocean, as the species is a key reef building coral at the atoll. In this study, the local distribution and abundance of GAs was quantified to determine if this occurrence could be classified as an outbreak, and the effects of this disease on I. palifera on reproductive potential and growth was described using histological and geochemical analysis. Growth anomalies were documented at 75% of sites and affected approximately one third of the I. palifera colonies examined. This disease compromises the biological and reproductive functioning of the host, as evidenced by a significant reduction in the density of oocytes, mesenteries, polyps, and zooxanthellae in infected tissues in comparison to healthy tissue. Furthermore, geochemical analysis indicates changes to key trace elements may be the result of bioerosion processes by infecting bacteria and the reprecipitation of calcite. The results of this study indicate the division of energy to the rapid skeletal development that characterises the disease, may have occurred at the detriment of the future reproductive potential of the population.

There is currently no reliable geochemical proxy of historical coral bleaching. Here we test the hypothesis that increases in the nitrogen isotopic signature of coral tissue, which is recorded in skeletal-bound organic material (CS-δ15N), can be used to detect coral bleaching events in the past. We measured CS-δ15N in coral colonies that showed high density thermal stress bands associated with the 1998 and 2002 mass bleaching events on the central Great Barrier Reef. Analysis of coral cores from 2 inshore and 1 mid-shelf reef found that increases in CS-δ15N occurred either side of the thermal stress events and were therefore unlikely to be a physiological response to bleaching. We then assessed whether CS-δ15N could be used to detect shelf-wide upwelling, which has been previously shown to coincide with mass bleaching events. For the inshore sites the response of CS-δ15N to upwelling was not uniform between reefs or between colonies from the same reef. However, on the mid-shelf reef, increased CS-δ15N during the known upwelling of 1998 was more consistent between cores. Analysis of a 23-year old coral core from the mid-shelf reef showed increased CS-δ15N between 1983–1985 and 1997–2000, periods where strong El Nino events were proceeded by intense wind-driven upwelling. We conclude that coral CS-δ15N is not a direct proxy for coral bleaching but can be used to detect prolonged and pervasive upwelling that coincides with mass bleaching events. Further validation with longer core records is required.

A survey conducted in Fall 2017 by US Navy scientists around the small, uninhabited island of Farallon de Medinilla (FDM) documented severe bleaching related to extended regional heat stress. Three of the dominant scleractinian genera at FDM, Pocillopora, Leptastrea, and Astreopora, were severely impacted, with more than 90% of colonies from many species exhibiting bleaching. In contrast, several species of Porites corals, another dominant genus at FDM, fared better, with less bleaching (7%–68% by species) than the island average (78%). Bleaching was somewhat higher at shallower depths (1 knot that precluded diving, rare but potentially hazardous ordnance items, survey requirements for georeferenced imagery, and quantitative data collection. The survey protocol designed to accommodate these challenges is presented here, as are lessons from an unsuccessful attempt to delineate bleached coral colonies in photographs using automated object-based image analysis.

Marine waters surrounding Child-friendly Integrated Public Spaces (RPTRA) at Tanjung Elang still has the potential for highly productive coral reef resources, thus enabling the development of ecological-based tourism, education and conservation. Despite the potential, the coral reefs in the surrounding of RPTRA Tanjung Elang has suffered damage caused by anthropogenic activities and natural factors. The aim of this research is to assess the initial condition of coral reef at the location of marine park areal and coral reef education center plan, RPTRA Tanjung Elang Waters, Pramuka Island, Seribu Islands National Park, DKI Jakarta, Indonesia. This research used Underwater Photo Transect/UPT method were analyzed using CPCe 4.1. software (Coral Point Count with Excel extension). The results of physico-chemical parameters measurements showed that water quality in RPTRA Tanjung Elang Waters Pramuka Island, is still within tolerance limits for coral life. The percentage of live coral cover was in a bad category with a low value (5.35%). The most dominant form of coral growth was submassive (CS) with a percentage value 54.46%. Composition of hard coral genusis consists of 3 family, 5 genus, and 100 species.The most dominant of Porites was with submassive and massive growth form. The index value of diversity shows a low category (0.56). The dominance index value showed a medium category (0.75). Uniformity and mortality index value showed a low category (0.35 and 0.43).

Coral ecosystems in the central Mexican Pacific inhabit environmental conditions considered as suboptimal for reef development, such as wide ranges in temperature, low pH, and cyclonic activity. In addition, they are facing increasing nutrient and sediment inputs as a consequence of urban growth and tourism. While the global effects of anthropogenic stressors to coral communities have been described, the local response and microscale variations remain unknown. Therefore, the present study evaluates three physiological markers during 2018 (total lipid content, symbiont density, and chlorophyll a concentration) in the main reef-building coral genera (Pocillopora, Porites, and Pavona) from two coral communities: one coastal site next to a luxury touristic development with high sedimentation rates and elevated nutrient inputs from golf courses, and one at an insular MPA 6 km distant from the coast and where human activities are regulated. At each coral sampling site, nitrite, nitrate, and phosphate concentrations as well as sedimentation rates were measured. The analyses of the physiological markers showed significant differences in the lipid content and symbiont density between sites, with corals at Isla Larga presenting higher lipid content but lower symbiont density, while pigment concentration only differed across months. When assessing differences among coral genera, Pocillopora colonies presented the highest lipid content, while Pavona showed more symbionts and Porites colonies the uppermost pigment concentrations, with significant differences among genera and across the studied months. Environmental characterization showed significant differences between sites in the nitrate concentration and sedimentation rates. Generalized nonlinear models evidence that lipid concentration is related to sedimentation rates and temperatures, symbiont density to nitrite and phosphate concentrations, and pigment concentrations to nitrate and phosphate concentrations as well as sedimentation rates.

Scleractinian corals often reproduce in synchronized spawning events to maximize gamete fertilization and coral larval production. The extent of spawning synchrony and its timing vary among coral taxa and among biogeographic regions. Information is, however, limited, especially for equatorial reefs, hindering the identification of environmental cues that influence gametogenic cycles and spawning. To investigate the timing of gamete maturation and spawning in Palau and their association with environmental cues, we monitored tagged colonies from 11 common coral species within three families over 21 months. We then combined our findings with previous available information to more broadly summarize the known coral spawning patterns in Palau. In combination with previous observations, our data confirmed the occurrence of an extended coral spawning season in Palau, spreading over 9 months. Some coral taxa participated in synchronous multispecific spawning events, with the largest occurring throughout April and May. Other coral taxa, including Montipora corals, displayed inter- and intra-specific spawning asynchrony. Consequently, environmental cues associated with spawning patterns differed among species. The largest Acropora spawning event of the year (March–April) was associated with the lowest yearly high tides and a monthly mean sea surface temperature around 29 °C. Massive Porites spawned predominantly in April and May, associated with increased monthly levels of solar insolation. Porites rus spawned in June–August and was associated with longest monthly day length. Our study demonstrates that Palauan coral assemblages have complex patterns of multispecific spawning events throughout most of the year, which may have important implications for larval dispersal, supply and recruitment patterns, influencing the resilience of coral reefs in this region.

Coral reefs are of global concern in the face of increasing anthropogenic disturbance. Much research has focused on the negative factors associated with coral reef decline, but few have documented the positive factors in relation to recovering coral reefs. Here, we report a positive quantitative association between sea urchins (diadematids), coral recruitment and coral recovery, recorded along Taiwanese coral reefs. We monitored coral cover change, juvenile coral density, herbivore density (fishes, sea urchins, gastropods) and macroalgal cover, along three reefs between 2012 and 2015. Multivariable regression analyses revealed that sea urchin (diadematids) density was the primary (positive) driver, explaining 74% of variation in coral cover change and 89% in coral juvenile density among sites and years. The relationship between sea urchin density and coral juvenile density was especially evident for four common coral genera: Acropora, Dipsastraea, Pocillopora and Porites. These results suggest that diadematid urchins enhance coral recovery on these reefs by promoting the recruitment of corals. The density of juvenile corals was also found to explain 67% of variation in coral cover change, highlighting the potential use of coral juvenile density as a proxy for coral recovery potential in coral resilience studies.

The Krakatau Islands in the Sunda Strait have been significantly impacted by catastrophic volcanic eruptions in 1883 and 2018. The marine habitats are not well studied, neither in the past nor in the present. This research is a report on the distribution and ecology of corals and sponges in the Krakatau Volcanic Complex at the three islands of Anak Krakatau, Rakata, and Panjang. This study used 100 m transects long in 5–7 m depth. Hard coral and soft coral communities are found to live with a coverage varied between 25-53% and 0-24%. Dead coral skeletons covered 14–40% of the surveyed area and did not seem to affect the abundance of sponges recorded. The Sponges occupied 0–6% of the area, and they often acted as coral competitors, shaping the benthic ecosystems. The recorded sponges only belong to the Demospongiae class, which are the Suberitid species that are commonly found in Indonesian waters, e.g., Amorphinopsis excavans, Protosuberites collaris, and Terpios sp. The excavating sponge Cliona cf. orientalis was frequently found to be a successful competitor of massive Porites sp., aggressively overgrowing live parts of the coral. Two Haliclona species and Mycale relicta colonized dead coral skeleton. Overall, the benthic communities appear healthy and are comparable to other similar locations that are not affected by volcanic activity.

Increasing incidence of major disturbances is contributing to extensive and widespread coral loss, thereby undermining the biodiversity, structure and function of reef ecosystems. The composition of coral assemblages is already changing due to selective effects of recurrent disturbances, combined with marked differences in the underlying life-history dynamics of corals, which affects their recovery. This study quantifies the effects of varying disturbance regimes on two groups of corals with divergent life histories: short-lived species with rapid growth (bushy and tabular Acropora) and long-lived species with slow growth (massive and columnar Porites). Inter-decadal shifts in the coral assemblages across four locations suggest that a high frequency of moderate disturbances favours Porites, whereas infrequent, but severe disturbances favour rapidly replenishing Acropora. Using empirical modelling, we expand these observations to show that Acropora continues to dominate so long as the interval between major disturbances is > 2 years. The only disturbance regime we considered that favoured Porites was high frequency (2-year recurrence) of moderate disturbance, whereas high frequency of severe disturbances led to local extirpation of both Acropora and Porites. Our results show that increasing incidence of major disturbances will not necessarily lead to selective loss of species that are most susceptible to disturbance, as long as these species can continue to colonise vacant space and grow quickly in the aftermath of such disturbances. This study highlights the need to consider the sensitivity of taxa to changes in both disturbance frequency and severity when forecasting changes in the composition of coral assemblages under new disturbance regimes.

Widespread coral bleaching occurred in the central Red Sea in 2010 and 2015. During both events, a cross-shelf and depth gradient of bleaching severity was identified within the Thuwal reef system, central Red Sea, Saudi Arabia. While bleaching and survival of coral taxa were monitored, neither in situ reef temperatures nor coral-associated algal communities (family Symbiodiniaceae) were characterized. Here, we determined coral host-associated Symbiodiniaceae communities and monitored temperatures along the same cross-shelf and depth gradient on six reefs in 2017 to better understand the role of these factors in the observed bleaching patterns and to generate a baseline for further studies. We characterized > 600 coral–algal associations across winter and summer in six genera of scleractinian coral (Pocillopora, Stylophora, Seriatopora, Galaxea, Gardineroseris, and Porites) and one fire coral (Family Milleporidae) using ITS2 next-generation sequencing in conjunction with the SymPortal analytical framework. We show that previous bleaching patterns correlate poorly with the largely coral host-specific structure of the 2017 Symbiodiniaceae community and are in better agreement with absolute and intraday sea water temperature variations monitored on the reefs. We demonstrate a greater distinctiveness of Symbiodiniaceae communities at the more severely bleached inshore reefs compared to those reefs further offshore. However, the potential Symbiodiniaceae community changes at these reefs prior to our sampling prevent us from evaluating this distinctiveness as determinative of the differences in bleaching severities. Based on our analyses, we discuss how fine-scale delineation of algal genotypes, including host-specific putative genotypes of Durusdinium trenchii that represent alluring targets for further taxonomic identification, corroborate a niche-adapted rather than generalist character of many coral–Symbiodiniaceae associations. In conclusion, as studies such as this one continue to build the global catalogue of coral–Symbiodiniaceae associations, we may be afforded a better oversight of how specialized coral–algal associations really are and how restricted their modification may be, both of which are critical considerations in predicting the adaptive potential of corals and the reef ecosystems they build.

The annual banded skeletons of reef corals potentially record past earthquakes events. We examined cores of five living Porites coral heads in Simeulue Island, Indonesia, near the epicenter of the 2004 Sumatra-Andaman and the 2005 Nias-Simeulue earthquakes. These sites showed 0.4–1.4 m of uplift. We measured skeletal strontium, magnesium, and calcium; carbon and oxygen isotopic ratios; and skeletal density, extension, and calcification rates, from 1994 to 2010. Coral geochemistry fluctuates more than are expected from strictly environmental causes; however, stress bands, reduced growth rates, and changed skeletal δ13C appear to reflect the tsunami and seismic uplift (the step change in skeletal δ13C results equated to 0.31 ± 0.10‰/m in response to the 2004 uplift and 0.23 ± 0.03‰/m to the 2005 uplift).

Bioerosion by reef-dwelling organisms influences net carbonate budgets on reefs worldwide. External bioeroders, such as parrotfish and sea urchins, and internal bioeroders, including sponges and lithophagid bivalves, are major contributors to bioerosion on reefs. Despite their importance, few studies have examined how environmental (e.g., nutrients) or biological drivers (e.g., the actions of other bioeroders) may influence bioeroder dynamics on reefs. For example, internal bioeroders could promote external bioerosion by weakening the coral skeletal matrix. Our study investigated: (1) whether nutrient supply influences the dynamics between internal and external bioeroders and (2) how the presence of a boring bivalve, Lithophaga spp., influences parrotfish bioerosion on massive Porites corals. We hypothesized that nutrient supply would be positively correlated with Lithophaga densities on massive Porites colonies, and that as bivalve density increased, the frequency and intensity of parrotfish bioerosion would increase. To test these hypotheses, we analyzed six time points over a 10-yr period from a time series of benthic images and nitrogen content of a dominant macroalga from the fringing reefs around Moorea, French Polynesia. We found Lithophaga densities were positively correlated with nitrogen availability. Further, massive Porites that are more infested with Lithophaga had both a higher probability of being bitten by parrotfish and a higher density of bite scars from parrotfishes. Our findings indicate that increasing nutrient availability may strengthen the relationship between internal and external bioeroders, suggesting that colonies at more eutrophic sites may experience higher bioerosion rates.

The distribution and organisation of benthic organisms on tropical reefs are typically heterogenous yet display distinct zonation patterns across depth gradients. However, there are few datasets which inform our understanding of how depth zonation in benthic community composition varies spatially among and within different reef systems. Here, we assess the depth zonation in benthic forereef slope communities in the Central Indian Ocean, prior to the back-to-back bleaching events in 2014–2017. We compare benthic communities between shallow (5–10 m) and deep (20–25 m) sites, at two spatial scales: among and within 4 atolls. Our analyses showed the variation in both major functional groups and hard coral assemblages between depth varied among atolls, and within-atoll comparisons revealed distinct differences between shallow and deep forereef slope communities. Indicator taxa analyses characterising the hard coral community between depths revealed a higher number of coral genera characteristic of the deep forereef slopes (10) than the shallow forereef slopes (6). Only two coral genera consistently associated with both depths across all atolls, and these were Acropora and Porites. Our results reveal spatial variation in depth zonation of benthic communities, potentially driven by biophysical processes varying across depths and atolls, and provide a baseline to understand and measure the impacts of future global climate change on benthic communities across depths.

The Taputapuatea marae of Ra’iatea is an emblematic landmark known throughout the world and sacred place for the Ma’ohi of Eastern Polynesia and the centre of a vast political-religious-cultural network in the Polynesian triangle. The erected stones constituting the ahu have been described as “limestone slabs” without precision by previous authors. These are in fact microatolls: corals (Porites) living in very shallow water and developing laterally, with a growth in height being limited by the lowest tide at the time of growth. A total of 38 samples were U/Th dated, of which 19 microatolls result in ages between 3 and 5 millennia. These are fossil microatolls that existed at a Holocene sea level of 0.80 m higher than today, when the Polynesians had not yet arrived. Other samples (molluscs, coral filling blocks) date back to the construction of the marae during the 17th-18th centuries. We hypothesize that the erected microatolls of the ahu were collected by Polynesians at the site and that others are still underground.

We present a monthly dataset (AD 2002–2005) of rare earth elements (REEs) recorded in Porites coral, which were obtained from the Weizhou Island (WZI), Beibu Gulf, northwest of South China Sea (SCS). This offshore coral shows a strong seasonal cycle in REE/Ca ratios, with enriched REEs (total REEs, 100~140 ppb) in winter and depleted REEs (40~60 ppb) in summer. Since the influence of the river discharge is limited to the river mouth, its contribution to the dissolved REEs is negligible for the offshore area of WZI. Given the similar seasonal pattern of Ba/Ca, we suggest that the remobilization of REEs from river-transported sediments on the shelf of SCS through winter monsoon-driven mixing is the major source of REEs to WZI. Moreover, the peak time of the Nd/Yb ratio (occurred in spring) is not coupled with the occurrence of the maximum REEs, which could mainly be attributed to the degradation of biogenic particles that causes more light REE released in comparison to heavy REE. The Ce anomaly also displays a distinct seasonality (i.e., enhanced anomaly in winter and summer and diminished anomaly in spring), likely reflecting the microbial oxidation activities driven by seasonal temperature and nutrient cycles. Large Gd anomaly (Gd/Gd* up to 1.7) recorded in coral skeletons is unlikely originated from the natural sources, but reflects anthropogenic activities through the recent excessive use of Gd complexes by magnetic resonance imaging of medical examination in this region. Keywords: Coral, Rare earth element, Winter monsoon, South China sea

Coral reefs are experiencing a dramatic loss of hard coral abundance and associated habitat structure from a myriad of local and global factors. Here, utilizing U–Th radiometric age-dating of coral death assemblages, we investigated patterns of coral mortality from the eastern margin of the Red Sea along a latitudinal gradient (Yanbu, 24o N; Thuwal, 22o N; Al-Lith, 19o N; Farasan Banks, 18o N) in 2018 and 2019. In all four regions, radiometric ages of in situ dead Acropora and Pocillopora colonies were largely confined to the late twentieth and early twenty-first century. During the early twenty-first century, coral mortality was found to be synchronous with previously documented bleaching events in 2010 and 2015 and, at one site (Farasan Banks), an outbreak of crown-of-thorns starfish (COTS) in 2009. The most northern site, Yanbu, had the highest relative percentage of live coral (42 ± 4%) and of living Acropora, and may serve as a refugium under climate warming scenarios. For the three southern regions (Thuwal, Al-Lith, Farasan Banks) benthic structure was mostly comprised of dead corals. The southernmost survey site, Farasan Banks, underwent a dramatic change in coral benthic structure associated with a COTS outbreak in 2009 and a bleaching event in 2015, and had the lowest relative percentage of live coral (6 ± 2%), comprised mostly of massive Porites, with no live Acropora or Pocillopora. Our results highlight the asynchronous impact of disturbance events on eastern Red Sea coral reefs and emphasize regional differences in recovery and ecosystem state.

Land-based sediment stress represents a threat to many coral reefs in Puerto Rico primarily as a result of unrestricted land cover/land use changes and poor best management practices. The effects of such stresses have been documented along most coasts around the island. However, little attention has been paid to reefs located on the north coast, and very little is known about their composition and current state. Here, we present a study characterizing riverine inputs, water quality conditions, and benthic composition of two previously undescribed coral reefs (Tómbolo and Machuca reefs) located just eastward of the Río Grande de Manatí outlet in north-central Puerto Rico. This study utilizes a time series of remotely sensed ocean color products [diffuse vertical attenuation coefficient at 490 nm (Kd490) and chlorophyll-a concentration (Chl-a) estimated with data from the Visible Infrared Imaging Radiometer Suite (VIIRS)] to characterize water quality in this coastal region. In general, the months with relatively high mean daily river streamflow also coincide with months having the highest proportion of eastward wave direction, which can promote the eastward influence of river waters toward the two coral reefs sites. Kd490 and Chl-a showed a higher riverine influence closer to the watershed outlet. Kd490 and Chl-a monthly peaks also coincide with river streamflow highs, particularly at those pixels closer to shore. Tómbolo Reef, located farther eastward of the river outlet, shows a well-developed primary reef framework mainly composed of threatened reef-building species (Acropora palmata, Pseudodiploria) and high coral cover (19–51%). The benthos of Machuca Reef, located closer to the river outlet, is dominated by macroalgae with a significantly lower coral cover (0.2–2.7%) mainly composed of “weedy” coral species (Porites astreoides and Siderastrea radians). Cover of major benthic components correlates with distance from the river outlet, and with gradients in Kd490 and Chl-a, with higher coral cover and lower macroalgal cover farther from the river outlet. Coral cover at Tómbolo Reef is higher than what has been reported for similar sites around Puerto Rico and other Caribbean islands showing its ecological importance, and as up until now, an unrecognized potential refuge of reef-building threatened coral species.

Polapa FS, Werorilangi S, Ali SM, Jompa J. 2021. Physiological responses of scleractinian corals in marginal habitat. Biodiversitas 22: 4011-4018. This study aims to analyze physiological differences in corals in marginal habitats. Under different conditions, the production/respiration (P/R) ratio and photobiology of various coral genera were compared. Samples were taken from three coral reef zones representing typical reef habitats and from the mangrove ecosystem as a marginal habitat. Surveys revealed two coral genera surviving in extreme conditions (marginal habitat). The P/R ratio measurements indicated that corals living in the mangrove ecosystem tend to be heterotrophic. This was supported by observations of colonies with tentacles extended from the corallites. Furthermore, Porites living in the mangrove habitat consume more O2 directly than saving it for other purposes, such as growth. The genus Dipsastraea exhibited elevated zooxanthellae density in the mangrove ecosystem, whereas Porites exhibited similar densities in both ecosystems.

Tropical shallow-water reefs are the most diverse ecosystem in the ocean. Its persistence rests upon adequate calcification rates of the reef building biota, such as reef corals. Optimum calcification rates of reef corals occur in oligotrophic environments with high seawater saturation states of aragonite (Ωsw), which leads to increased vulnerability to anthropogenic ocean acidification and eutrophication. The calcification response of reef corals to this changing environment is largely unknown, however. Here, we present annually and sub-annually resolved records of calcification rates (n = 3) of the coral Porites from the nutrient rich and low Ωsw Arabian Sea upwelling zone (Masirah Island, Oman). Calcification rates were determined from the product of skeletal extension and bulk density derived from X-ray densitometry. Compared to a reference data set of coral skeletons from typical reef environments (Great Barrier Reef, Hawaii), mean annual skeletal bulk density of Porites from Masirah Island is reduced by 28 %. This density deficit prevails over the entire year and probably reflects a year-round low saturation state of aragonite at the site of calcification (Ωcf), independent of seasonal variations in Ωsw (e.g. upwelling). Mean annual extension rate is 20 % higher than for the reference data set. In particular, extension rate is strongly enhanced during the seasons with the lowest water temperatures, presumably due to a high PO43−/NO3−-ratio promoting rapid upward growth of the skeleton. Enhanced annual extension attenuates the negative effect of low density on calcification rate from −25 % to −11 %, while sub-annual calcification rates during the cool seasons even exceed those of the reference corals. We anticipate optimal nutrient environments (e.g. high PO43−/NO3−-ratios) to have significant potential to compensate the negative effect of ocean acidification on reef coral calcification, thereby allowing to maintain adequate rates of carbonate accumulation, which are essential for preserving this unique ecosystem.

The structure of ecosystems is usually determined by the shape of the organisms that build it, commonly known as ecosystem engineers. Understanding to what extent plasticity and environmental filtering determine variation in ecosystem engineer physical structure is necessary to predict how ecosystem structure may change. Here, we explored coral survival and the plasticity of morphological traits that are critical for habitat provision in coral reefs. We conducted a reciprocal clonal transplant experiment in which branching corals from the genus Porites and Acropora were moved to and from a deep and a shallow site within a lagoon in the Maldives. Survival and trait analyses showed that transplant destination consistently induced the strongest changes, particularly among Acropora spp. The origin of the corals only marginally affected some of the traits. We also detected variation in the way individuals from the same species and site differentiate their shape, showing that traits linked to habitat provision are phenotypically plastic. The results suggest coral phenotypic plasticity plays a stronger role than environmental filtering, in determining zonation of coral morphologies, and consequently the habitats they provide for other taxa.

Thermal-stress events have changed the structure, biodiversity, and functioning of coral reefs. But how these disturbances affect the dynamics of individual coral colonies remains unclear. By tracking the fate of 1069 individual Acropora and massive Porites coral colonies for up to 5 years, spanning three bleaching events, we reveal striking genus-level differences in their demographic response to bleaching (mortality, growth, and recruitment). Although Acropora colonies were locally extirpated, substantial local recruitment and fast growth revealed a marked capacity for apparent recovery. By contrast, almost all massive Porites colonies survived and the majority grew in area; yet no new colonies were detected over the 5 years. Our results highlight contrasting dynamics of boom-and-bust vs. protracted declines in two major coral groups. These dangerous demographics emphasise the need for caution when documenting the susceptibility and perceived resistance or recovery of corals to disturbances.

Ocean acidification (OA) is negatively affecting calcification in a wide variety of marine organisms. These effects are acute for many tropical scleractinian corals under short-term experimental conditions, but it is unclear how these effects interact with ecological processes, such as competition for space, to impact coral communities over multiple years. This study sought to test the use of individual-based models (IBMs) as a tool to scale up the effects of OA recorded in short-term studies to community-scale impacts, combining data from field surveys and mesocosm experiments to parameterize an IBM of coral community recovery on the fore reef of Moorea, French Polynesia. Focusing on the dominant coral genera from the fore reef, Pocillopora, Acropora, Montipora and Porites, model efficacy first was evaluated through the comparison of simulated and empirical dynamics from 2010–2016, when the reef was recovering from sequential acute disturbances (a crown-of-thorns seastar outbreak followed by a cyclone) that reduced coral cover to ~0% by 2010. The model then was used to evaluate how the effects of OA (1,100–1,200 µatm pCO2) on coral growth and competition among corals affected recovery rates (as assessed by changes in % cover y−1) of each coral population between 2010–2016. The model indicated that recovery rates for the fore reef community was halved by OA over 7 years, with cover increasing at 11% y−1 under ambient conditions and 4.8% y−1 under OA conditions. However, when OA was implemented to affect coral growth and not competition among corals, coral community recovery increased to 7.2% y−1, highlighting mechanisms other than growth suppression (i.e., competition), through which OA can impact recovery. Our study reveals the potential for IBMs to assess the impacts of OA on coral communities at temporal and spatial scales beyond the capabilities of experimental studies, but this potential will not be realized unless empirical analyses address a wider variety of response variables representing ecological, physiological and functional domains.

Local adaptation to different environments may reinforce neutral evolutionary divergence, especially in populations in the periphery of a species’ geographic range. Seascape genomics (high-throughput genomics coupled with ocean climate databases) facilitates the exploration of neutral and adaptive variation in concert, developing a clearer picture of processes driving local adaptation in marine populations. This study used a seascape genomics approach to test the relative roles of neutral and adaptive processes shaping population divergence of a widespread coral reef snail, Coralliophila violacea. We collected C. violacea from colonies of their coral host (Porites spp.) at ten locations spanning a large portion of their geographic range. We used RAD-seq to investigate possible local adaptation via genetic-environmental associations with five ocean climate variables. Four genetic partitions were concordant with regions previously observed in mtDNA (Indian Ocean, Coral Triangle, and Hawaiian Islands), with the addition of Vietnam and varying isolation and admixture levels. We identified outlier loci (FDR = 0.10, N = 72) among individual localities and between regions (FDR = 0.10, N = 34), suggesting that some loci are putatively under divergent selection. Association analyses showed that the two strongest drivers of local adaptation were the annual range and mean of sea surface temperature. Populations that experience lower sea surface temperatures at the periphery of C. violacea’s geographic range drive these associations. Our results show that local adaptation to different environments likely reinforces neutral divergence, especially in peripheral populations.

Herbivores play an integral part in maintaining the health of coral reefs by suppressing the growth of algae and accumulation of sediment and facilitating coral growth. However, in predator-depleted systems where densities of herbivores are unnaturally high, grazing can have detrimental effects on corals through excessive bioerosion. Yet, these benefits and costs are rarely investigated concurrently, especially in eutrophic systems where grazers may play a disproportionate role. We used a year-long exclusion experiment to elucidate the effect of natural densities of the dominant herbivore (the sea urchin Diadema setosum) on coral communities in a heavily fished and eutrophic system (Hong Kong, China). To assess benthic community response to grazing, we monitored the survival and growth of three locally abundant coral species (Pavona decussata, Platygyra carnosus and Porites sp.), algal and sediment accumulation, and bioerosion of coral skeletons across seasons. We found that urchins maintained our experimental coral assemblages, and when excluded, there was a 25 to 75-fold increase in algal-sediment matrix accumulation. Contrary to predictions, there was no general response of corals to urchin presence; Porites sp. survivorship increased while P. decussata was unaffected, and growth rates of both species was unchanged. Surprisingly, P. carnosus experienced higher mortality and bioerosion of up to 33% of their buoyant weight when urchins were present. Therefore, under natural densities, sea urchins clear substrate of algae and sediment, increase survival, maintain growth rates and health of coral assemblages, yet can accelerate the bioerosion of species with porous skeletons following mortality.

Reefs are biogenic structures that result in three-dimensional accumulations of calcium carbonate. Over geological timescales, a positive balance between the production and accumulation of calcium carbonate versus erosional and off-reef transport processes maintains positive net accretion on reefs. Yet, how ecological processes occurring over decadal timescales translate to the accumulation of geological structures is poorly understood, in part due to a lack of studies with detailed time-constrained chronologies of reef accretion over decades to centuries. Here, we combined ecological surveys of living reefs with palaeoecological reconstructions and high-precision radiometric (U-Th) age-dating of fossil reefs represented in both reef sediment cores and surficial dead in situ corals, to reconstruct the history of community composition and carbonate accumulation across the central and southern Saudi Arabian Red Sea throughout the late Holocene. We found that reefs were primarily comprised of thermally tolerant massive Porites colonies, creating a consolidated coral framework, with unconsolidated branching coral rubble accumulating among massive corals on shallow (5–8 m depth) exposed (windward), and gently sloping reef slopes. These unconsolidated reef rubble fields were formed primarily from ex situ Acropora and Pocillopora coral fragments, infilled post deposition within a sedimentary matrix. Bayesian age-depth models revealed a process of punctuated deposition of post-mortem coral fragments transported from adjacent reef environments. That a large portion of Saudi Arabian Red Sea reef slopes is driven by allochthonous deposition (transportation) has important implications for modeling carbonate budgets and reef growth. In addition, a multi-decadal lag exists between the time of death for branching in situ coral and incorporation into the unconsolidated reef rubble. This indicates that recent climate related degradation in the 21st century has not had an immediately negative effect on reef building processes affecting a large portion of the reef area in the Saudi Arabian Red Sea.

Low-Voltage Mineral Deposition technology (LVMD), widely known as Biorock, has previously been suggested as support for coral reef restoration, as hypothesized high porosity, wide pore-size distribution and connectivity, and good strength properties may facilitate biological functions (for example larvae settlement) and durability. In this technology, very low voltage induces an electrical current that initiates precipitation and accretion of hard minerals (aragonite and calcite) on a metal in seawater. This technology has been discussed mainly for its biological value, while this paper wants to highlight also its engineering value as artificial reef material. Indeed, some of the properties that makes it valuable in one domain are also supporting its use in the other. Because the metal on which the precipitation takes place can be of any shape and size, so can the artificial reef and its mechanical strength characteristics are above the ones of corals and similar to concrete, indicating adequate durability. Coral and boulder reefs suffering from degradation have severe implications on biodiversity, protection from flooding, and cultural value and therefore understanding how to persevere and re-establish these ecosystems is central for sustainable intervention in the marine environment. By comparing chemical-physical characteristics of Coral Porites Exoskeleton (CPE), one typical reef building coral type, LVMD and High-Voltage Mineral Deposition (HVMD), we show that they possess highly similar properties including chemical composition, density, total porosity, pore-size distribution, physical and chemical heterogeneity, total and external surface areas, and comparable mechanical strength.

Despite the economic and ecological importance of corals’ skeletal structure, as well as their predicted vulnerability to future climate change, few studies have examined the skeletal mechanical properties at the nanoscale. As climate change is predicted to alter coral growth and physiology, as well as increase mechanical stress events (e.g., bioerosion, storm frequency), it is crucial to understand how skeletal mechanical properties change with environmental conditions. Moreover, while material properties are intimately linked to the chemical composition of the skeleton, no previous study has examined mechanical properties alongside carbonate geochemical composition. Using Porites coral cores from a wide range of reef environments (Thailand, Singapore, Taiwan), we correlated coral’s micro-mechanical properties with chemical composition. In contrast to previous mechanical measurements of reef-building corals, we document unprecedented variability in the hardness, stiffness, and micro-cracking stress of Porites corals across reef environments, which may significantly decrease the structural integrity of reef substrate. Corals from environments with low salinity and high sedimentation had higher organic content and fractured at lower loads, suggesting that skeletal organic content caused enhanced embrittlement. Within individual coral cores, we observed seasonal variability in skeletal stiffness, and a relationship between high sea surface temperature, increased stiffness, and high-density. Regionally, lower Sr/Ca and higher Mg/Ca coincided with decreased stiffness and hardness, which is likely driven by increased amorphous calcium carbonate and skeletal organic content. If the coral is significantly embrittled, as measured here in samples from Singapore, faster erosion is expected. A decrease in skeletal stiffness will decrease the quality of reef substrate, enhance the rate of bioerosion by predators and borers, and increase colony dislodgement, resulting in widespread loss of structural complexity.

Reproduction and recruitment are essential processes for the continued success of coral communities. Islas Marias Archipelago is considered a connectivity node among coral communities distributed along the Northeastern Tropical Pacific (NTP); as such, sexual reproduction of scleractinian corals affects the maintenance of the local populations and the long-distance connectivity of reefs across the region. In this study, successful sexual reproduction in the species of the three most abundant scleractinian corals genera was demonstrated, in part by documenting gamete presence and maturation in tissues and spatio-temporal variability in juvenile coral settlement, which were quantified across substrate type, habitat quality, and environmental factors. Only 12 larvae recruited (ten Porites, two Pavona) to artificial substrates, and monthly recruitment density of 1.82 ± 0.23 recruits m−2 (n = 383) was recorded on natural substrates. There were significant differences between genera, with Porites producing the highest density of recruits (0.60 ± 0.45 recruits m−2, followed by Pavona (0.52 ± 0.24 recruits m−2) and Pocillopora (0.28 ± 0.06 recruits m−2). The highest coral recruitment was observed at Baby Reef (2.57 ± 0.46 recruits m−2), followed by Cleofas II (1.81 ± 0.21 recruits m−2) and Japanese Garden (1.24 ± 0.46 recruits m−2); the former site was characterized by the highest cover of crustose coralline algae. We found successful recruitment of the main reef-forming species in the Mexican Pacific and suggest that Islas Marias is a region of critical importance in terms of its function as a source of genetic variability, and, the generation of, new individuals that will be key to sustaining coral reef ecosystems in the NTP.

Here we investigate the fractionation of Mo isotopes (δ98MoNIST) in biogenic carbonates and assess its viability as an environmental and biological proxy in coral skeletons. An annually resolved 40-year record of δ98MoNIST values is reported for a Porites coral from the Great Barrier Reef (GBR), Australia. This, together with a four-day time-series of δ98MoNIST measurements of seawater and samples from a range of coral species from Luhuitou Reef in Sanya Bay, northern South China Sea is used to investigate the relative fractionation of Mo isotopes between coral and seawater and assess the potential of δ98MoNIST as a proxy for tracing biological activity. δ98MoNIST values in the GBR coral skeleton are lighter than those of seawater (2.05‰, relative to NIST SRM 3134) and display large variations from 0.63‰ to 1.73‰, with a mean of 1.29‰. A significant relationship was found between coral δ98MoNIST and sea surface temperature (SSTcal) in the GBR coral. These observations and the Luhuitou Reef seawater data indicate that temperature-mediated biological activity in coral polyps potentially modulate coral δ98MoNIST. A biological fractionation model is proposed to explain how symbiotic zooxanthellae produce the considerable variations in Mo isotopic composition measured in the GBR coral. This fractionation suggests that Mo isotopes could potentially be used as a proxy for biological processes in corals.

Previous studies have reported recent substantial declines in the growth rates of massive Porites corals under warming oceans. However, the majority of these reports are from inshore reefs, and few have explored growth responses in offshore reefs from remote locations with low levels of pollution, sedimentation or nutrient loading. Here, we examined continuous growth records of massive Porites from remote locations spanning a 25 degrees latitudinal gradient in the Indo-Pacific, including Palau, central Sulawesi, West Papua and the central Great Barrier Reef (GBR). Between 1982 and 2012, no significant changes in calcification or extension anomalies were observed at any study location, despite significant increases in sea surface temperature (SST) at all sites. Skeletal density increased linearly by similar to 0.4 % yr(-1) in Palau, but no change was found in Sulawesi, yet skeletal density showed a significant nonlinear change in West Papua and the GBR. Skeletal density displayed a significant positive linear relationship with SST at Palau and West Papua, whereas no relationship was observed in Sulawesi. In the GBR, skeletal density exhibited a nonlinear parabolic relationship with SST, with strong negative anomalies occurring following major thermal events. Unlike the ongoing declines in growth rates of inshore corals that have been widely reported, we found that calcification and extension anomalies of the majority of Porites from offshore remote locations do not appear to be exhibiting negative growth responses to warming SST. Our results suggest that reefs experiencing low levels of local stressors may show increased resilience to warming SST in an era of rapidly warming oceans.

The species lists of scleractinian hard corals in Peninsular Malaysia have not been updated for 15 years. The present study aimed to determine the diversity and abundance patterns of scleractinian hard corals at twenty eight fringing reef sites along the coast of Redang and Tioman Islands. Visual photograph analyses of the coral video transect method revealed a total of 128 species from 47 genera in Redang and 239 species from 55 genera in Tioman. Following recent taxonomy of scleractinian corals, coral surveys and past studies revealed a total of 166 species from 53 genera in Redang and 350 species from 67 genera in Tioman. Current data at both islands presented a total of 358 species from 69 genera and 15 families of scleractinian corals with an additional 8 new species records for the east coast of Peninsular Malaysia. Acropora, Montipora and Porites were the most dominant genera and were found distributed within the coral assemblages. The reefs around both islands can be categorized under “good” coral conditions with the live corals cover from 40.9% to 73.5%. Overall findings indicated that the less affected reef zones by coastal development and human activities at both islands have established good coral conditions and coral genera diversity.

Knowledge of extant biodiversity with accurate species boundaries is one of the crucial prerequisites for guiding conservation priorities in the face of global climate change. DNA taxonomy promises...