Arabian Coral Reefs: Insights from Extremes ABSTRACTS FOR ORAL PRESENTATIONS (Alphabetical by last name of first author)

Assessment of coral disease on northeastern Arabian reefs Aeby, G.; Work, T.; Howells, E.; Abrego, D.; Williams, G.; Burt, J. Disease is a natural component of all populations but disease outbreaks indicate a shift in the host- pathogen-environment triad of disease causation. Disease outbreaks in coral populations are occurring globally, and Arabian reefs are no exception. However, little work has been done to characterize diseases in this region. We examined coral disease at 17 sites across Abu Dhabi, Musandam, and Fujairah. Summertime surveys revealed 13 types of coral diseases including tissue loss of unknown etiology (white syndromes) in Porites, Platygyra, Dipsastrea, Cyphastrea, Acropora and Goniopora; growth anomalies in Porites, Platygyra, and Dipsastrea; black band disease in Platygyra, Dipsastrea, Acropora, Echinopora and Pavona; Porites bleached patches and Porites yellow-banded tissue loss disease. Across all reefs, the most widespread diseases were Platygyra growth anomalies (52.9% of all surveys), Acropora white syndrome (47.1%) and Porites bleached patches (35.3%). However, disease assemblages differed significantly among sub-regions with Abu Dhabi exhibiting the highest number of diseases and the greatest disease prevalence. Of particular concern, was a high number of localized outbreaks of tissue loss diseases (8 of 17 sites) primarily found in Abu Dhabi. Histopathological analyses revealed necrosis and varied potential disease agents including bacteria (Beggiatoa), fungi, metazoans, and algae associated with tissue loss diseases. Growth anomalies were characterized by proliferation of basal body wall (Acropora) or increased number and size of mesenterial filaments (Platygyra). Compared to coral reefs in the Indo-Pacific, Arabian reefs had unique diseases, e.g. Porites yellow-banded tissue loss, and a high number of localized outbreaks highlighting the need for further disease research.

Phylogenetic analysis reveals taxonomic uncertainty of some species of Merulinidae in the Persian Gulf Alidoost-Salimi, P.; Ghavam Mostafavi, P.; Chen, AC.; Pichon, M.; Alidoost Salimi, M. The coral fauna of the Persian Gulf is subsets of the general Indo-Pacific fauna, with about 10% of the total Indo-Pacific species are also found in the Persian Gulf. Merulinidae has high representatives’ species throughout the Indo-Pacific as well as in the Persian Gulf and the Red Sea. Three species Cyphastrea microphthalma, Favites pentagona and Platygyra daedalea occur in the most coral carpets of Iranian islands, but their molecular phylogeny has not been considered. The aim of this study is the investigation of phylogenetic relationship of these species collected from two Iranian islands (Abu-Musa and Sirri) with the conspecific sequences from different regions through analysis of portion of ribosomal DNA. The result showed the mentioned species are para-polyphyletic. Also, there is no divergence between Persian Gulf, the Gulf of Aden and Indo-Pacific specimens. The phylogeny three showed F. pentagona is relatively distinct from other Favites species. The C. microphthalma is split weakly into two groups, including the representative from Persian Gulf and Gulf of Aden. Concerning P. daedalea, our result reveals the existence of one low supported molecular lineage and Platygyra species were indistinguishable from each other in their clad. The relationships of these species and it's closely related conspecific remained unresolved, and more study with wide geographic sampling is needed. This genetic data is the first attempt regarding the comparison of connectivity between the Persian Gulf and Indo-Pacific.

Coral Bioerosion on the marginal reefs of northeastern Arabia Al-Mansoori N.; McParland D. ; Burt J. Northeastern Arabia represents a marginal, high-latitude province that is characterized by coral communities with limited framework development. Although there is growing awareness of regional patterns of coral accretion, the role of bioerosion in offsetting accretion is largely unknown. For the first part of the study we estimated levels of bioerosion in two regionally common and widely distributed reef building corals, Platygyra daedalea and Cyphastrea microphthalma. Bioerosion percentages were calculated using images of cross-sectioned slices cut from center of corals collected from four reefs across >500 km of coastline in the thermally extreme and hypersaline southern Arabian Gulf (Delma, Saadiyat, Ras Ghanada; SST annual range: 18.4-35.7°C, salinity: 40-46 psu) and in the more benign Sea of Oman (Dibba; SST range: 21.5-34.0 °C, salinity: 36-39 psu). Internal bioerosion varied across species and sites. Bioerosion was consistently higher in Cyphastrea than Platygyra at all sites, with Cyphastrea having three times higher erosion overall (mean: 26.7% vs. 8.8% skeletal area eroded, respectively). The second part of the study aims to find the rates of bioerosion in five sites along the southern Arabian Gulf by deploying standardized experimental coral blocks onto the reefs and retrieve them after 12 months to measure the rates of bioerosion by calculating the loss of calcium carbonate. The results of the rates can then be contrasted to rates of bioerosion measured in other reefs in other regions around the world, this will help us understand where the future lies of reefs in the Arabian Gulf.

Bleaching causes carbonate budget collapse and threatens reef structural integrity on Bahraini reefs AlMealla, R.; Edullantes, B.; Smith, DJ. and Hepburn, LJ. Coral reefs have been in the forefront of climate change threats, with rising sea surface temperatures (SST) contributing to intense and increasing episodes of global bleaching events. These episodes have impacted carbonate budget dynamics, contributing to reef framework degradation and influencing reefs ability to keep pace with sea level rise (SLR). Reefs in the Persian-Arabian Gulf (PAG) exist in harsh environmental conditions with temperatures ranging between 16-36◦C. Despite the high thermal thresholds (~35◦C) of corals in this region, extensive bleaching and high coral mortality has been reported regionally in 2017. In this study we quantify carbonate budgets on Bahraini reefs and the impact of the 2017 severe bleaching on their budgetary state. Results indicate an overall drop from 14.2±5.5% to 8.4±1.4% in hard coral cover. This is contributing to an alarming budgetary shift from a net positive to a negative state. We attribute this to the severe bleaching, which took place between June – September 2017, resulting in high coral mortality rates and subsequent reduced framework accretion. Predicted warming trends present a threat to the structural integrity of Bahraini reefs and their ability to keep pace with future SLR.

A revision of the Genus Montipora (F. Acroporidae) in the Red Sea Baird, A, Cumbo, V.; Beruman, M. Regions on the periphery of the Indo-Pacific Ocean, in particular the Red Sea, are thought to be a potentially important point of coral species origination and export of novel lineages into surrounding regions. However, molecular approaches have revealed that the traditional taxonomy of the Scleractinia is fundamentally flawed and in urgent need of revision using modern integrated approaches. For example, the ecologically important and species–rich genus Montipora was last revised in the 1980’s. Here, I revisit species boundaries in the genus Montipora using molecular and morphological techniques. The results suggest reasonable concordance between molecular and morphological groups and identifies morphological traits useful for species delimitation. This integrated approach offers great promise for a much needed revision of the entire genus.

Changes in reef fish assemblages following multiple bleaching events: A case study in the northern Persian Gulf (Kish Island)

Bargahi, H.R., Mohammad Reza Shokri, Farhad Kaymaram, Mohammad Reza Fatemi Despite numerous incidents of coral bleaching in the Persian Gulf, no study has investigated the changes in reef fish communities after bleaching events in this region. Accordingly, the present study examined the changes in density, species richness, assemblage structure, species composition and trophic groups of reef fish during the years 2003 to 2019 in Kish Island in the northern Persian Gulf. During this time period, two mass coral bleaching events occurred in Kish Island. Using fish belt transect method, reef fish were counted in six stations with the highest coral density within four periods including two periods before the occurrence of bleaching (2008-2003 and 2017-2014) and two periods after bleaching (2009-Winter and 2018-Winter). No significant difference was found in total fish abundance from summer 2003 and winter 2004 (pre-bleaching) towards summer 2007 and winter 2008 (post-bleaching). Likewise, no significant difference was found in total fish abundance from winter 2015 (pre-bleaching) towards summer 2017, winter 2018 and winter 2019 (post-bleaching). Variation in Margalef index, diversity (Shannon index) and evenness (Pielou index) demonstrated clear fluctuation across pre-bleaching and post-bleaching periods with an overall decrease after bleaching events. No significant difference was detected in the assemblage structure of reef fish between pre-bleaching and post-bleaching periods. The result showed no significant difference in assemblage structure of trophic groups between pre-bleaching and post-bleaching periods. Yet, variation in density of different trophic groups indicated an overall increase in carnivore and omnivore fish after bleaching events.

Latitudinal variation in thermotolerance of Porites lobata in the Red Sea Barreto, M.M; Schmidt-Roach, S.; Aranda, M Spatial environmental heterogeneity creates different selective pressures that can lead to genetic variability and species adaptation. Due to its latitudinal temperature gradient and extreme temperature conditions, the Red Sea constitutes an ideal location to investigate local adaptation in thermotolerance. This becomes particularly important in a context of global change, and the rise of assisted gene flow (i.e. the managed movement of individuals of different populations within the species range) as a tool to accelerate coral reef adaptation to climate change. In this study, we investigate differences in physiological response to temperature in the coral Porites lobata from different latitudes of the Red Sea, in order to evaluate the potential of applying assisted gene flow to Red Sea reefs. We performed a common garden experiment with colonies collected from three different locations in Saudi Arabia which have distinctive thermal regimes: Duba (North), Thuwal (Central) and Farasan islands (South). Five colonies from each location were fragmented and deployed in situ in early summer, at the thermally intermediate location, Thuwal. Bleaching and survival were surveyed regularly. Results showed significantly higher bleaching in fragments from Duba, followed by 65% mortality. Even though no bleaching was observed in fragments from Farasan island, mortality rates of around 30% indicated that other environmental parameters besides temperature may influence coral health and survival. These results suggest that a management approach of Red Sea coral reefs based on assisted gene flow alone may not be efficient, due to local adaptation to environmental conditions other than temperature.

Long-term growth rates and effects of extreme temperatures in Platygyra daedalea Bauman, AG; Dunshea, G; Cantin, N; Riegl, B; Vaughn, GO, McParland, D; Pratchett, MS; Heron, SF; Burt, JA; Howells, EJ Sustained coral growth is fundamental for maintaining the structure, function and resilience of coral reef ecosystems, but can be greatly constrained by extreme and rapidly changing ocean temperatures. Given tropical ocean temperatures are predicted to increase 1–3°C by 2100, it is important to understand the response of coral growth to natural variation in ocean temperatures, as well as to acute temperature stress events under current and future climate change. Corals in the southern Arabian/Persian Gulf already exist in this future temperature environment with summer seawater temperatures that regularly exceed 35°C and frequent bleaching events thus providing potential insights into the present limits of coral growth. Here, we investigated long-term growth rates in the locally common Platygyra daedalea along marked gradients in seawater temperatures in the southern Gulf and Oman Sea. Annual growth characteristics (linear extension, density and calcification) were measured in coral slices from 38 individual P. daedalea colonies then compared over a 14-year period, 2000–2013. Across all years, we found marked variation in annual growth rates within and between locations which likely reflects local environmental conditions. Evidence of high density stress bands and some partial mortality, particularly in the southern Gulf, corresponded with recurrent high thermal disturbances these corals have experienced. Sustained declines in calcification occurred over time in both locations and was generally driven by reductions in density rather than linear extension. Interestingly, two sites in the southern Gulf with the lowest historical calcification exhibited no further declines during the study, suggesting that some Gulf corals may have reached their lower growth limits or that thermal disturbance has been to frequent for growth to rebound.

Grazing activity in an extreme environment: the Gulf vs Sea of Oman Bento, R.C.; John A. Burt; David A. Feary; Grace O. Vaughan; Andrew S. Hoey Herbivory is a key process on coral reefs, maintaining a healthy balance between corals and benthic algae. While numerous studies have shown that a limited suite of species, the macroalgal browsers, are capable of removing macroalgae, most studies have been conducted on biodiverse, low-latitude reefs. It is unknown how these findings translate to marginal high-latitude reef environments. We used tiles with established algal communities to investigate the rates of herbivory, as well as to identify key herbivores species, in two marginal coral reef environments: the southern Arabian Gulf, a naturally extreme environment, and the northern Sea of Oman. Diurnal herbivory resulted in two-fold greater reduction in algal cover in the southern Arabian Gulf than the northern Sea of Oman (36.2 ± 5.9%.12h-1 and 19.2 ± 5.0%.12h-1 (mean ±SE), respectively). The opposite was observed for nocturnal herbivory, with the greatest reduction in algal cover being recorded in the northern Sea of Oman (28.2 ± 4.5%.12h-1) compared to the southern Arabian Gulf (11.1 ± 6.2%.12h-1). Analysis of video footage revealed the angelfish Pomacanthus maculosus was the dominant herbivore in the Arabian Gulf, accounting for 89.3% of total mass-standardized bites recording during diurnal periods. In contrast, macro-invertebrates (i.e., gastropods and Diadema setosum) were the dominant herbivores in the Sea of Oman. While previous studies in biodiverse reef systems have shown the important functional role of single species of rabbitfish and surgeonfish in algae removal, our results show that the abundant omnivore angelfish, P. maculosus, acts as a functionally important herbivore in the Gulf.

Investigating Sabellastarte sp. around the Arabian Peninsula Brown, S.; Rowe, K.; Burt, J.; Marshell, A.; Paulay, G.; Berumen, M. Sabellastarte sp. (Sabellidae) are found in warm and temperate waters around the world. Using morphological characteristics, a previous study narrowed the genus down to eight species. However, due to the homogeneous nature of their features, it was concluded that morphological data alone could not be used for the phylogeny of the genus, especially since these distinguishing features change during development, growth, and regeneration. To date, the species found in the Red Sea has been described as S. sanctijosephi but no genetic work has been completed to confirm the speciation and distribution. In the Arabian Sea and Arabian Gulf, based on morphological features and limited genetic analysis, the species is often described as S. spectabilis. In the present study, molecular markers (16s and CO1) and morphological data will be used to examine Sabellastarte sp. around the Arabian peninsula. Samples from Saudi Arabia, Oman, and United Arab Emirates will add to previous work on the monophyly of Sabellastarte. In addition, information on the substrate, depth, and color variation will be used to inform the habitat preference and distribution patterns of this understudied species.

Causes and consequences of the 2017 coral bleaching event in the southern Persian/Arabian Gulf Burt, J.; Paparella, F.; Al-Mansoori, N.; Al-Mansoori, A.; Al-Jailani, H. Coral reefs of the Persian/Arabian Gulf were the last to succumb to the effects of the global-scale mass coral bleaching event that began in 2015. This study examines the causes and consequences of the 2017 bleaching event on eight reefs located across >350 km of the southern basin of the Gulf. Using a combination of five years (2013-17) of reef-based temperature observations, local meteorological data, and water column modeling, we show that 2017 was characterized by an extended period of mid-summer calm when winds rarely exceeded breeze conditions, reducing evaporative heat loss and inducing dramatic warming compared with non-bleaching years (2013-2016). Reef-bottom temperatures in the Gulf in 2017 were among the hottest on record, with mean daily maxima averaging 35.9 ± 0.1 °C across sites, with hourly temperatures reaching as high as 37.7 °C. Across the southern Gulf corals spent nearly two months (mean: 55.1 ± 3.9 days) above bleaching temperatures and nearly two weeks above lethal temperatures (11.8 ± 2.4 days), substantially longer than in the non-bleaching years (2013-16), and equating with 5.5 °C- weeks of thermal stress as Degree Heating Weeks. As a result, 94.3% of corals bleached, and two-thirds of corals were lost to mortality between April and September 2017. Mortality continued after peak bleaching, and by April 2018 coral cover averaged just 7.5% across the southern basin, representing an overall loss of nearly three-quarters of coral (73%) in one year. This mass mortality did not cause dramatic shifts in community composition as earlier bleaching events had removed most sensitive taxa. An exception were the already-rare Acropora which were locally extirpated in summer 2017. Given the increasing frequency of mass bleaching in the Gulf and the above-global rates of regional warming, the capacity for recovery and the prognosis for the future of Gulf reefs is not optimistic.

Responses of Red Sea cryptic benthic communities and fish reef communities to a bleaching event Carvalho, S.; Villalobos, R.; Coker, D.; Aylagas, E.; Sola, J.; Pearman, J.; Cúrdia, J.; Langner, U.; Cadiz, R.; Berumen, M. Globally, bleaching events are becoming more frequent and intense with some regions experiencing dramatic declines in reef communities and limited recovery between disturbance events. In 2015-2016, a pan-tropical mass bleaching event hit the Red Sea with significant loss of live coral cover across reefs in the central Red Sea, the Farasan Islands, and the Farasan Banks (southern regions). As part of a long term monitoring program within the framework of the Saudi Aramco Center for Marine Environmental Observations, three permanent sites within three areas of the central Red Sea were assessed before and after the bleaching event. A total of 27 Autonomous Reef Monitoring Structures (ARMS) were deployed and retrieved following a two-year soaking period to assess the reef cryptobiome. In addition, fish surveys were conducted at the same depth (10m) along 20 m replicate transects (n=3). Here, we present the changes in the biodiversity patterns of two critical biological components of coral reefs, i.e. fish communities and the cryptobiome (both sessile and mobile organisms inhabiting hidden spaces within the structures) before and after the last major bleaching event in the region. Results from this study provide us with a unique opportunity to investigate changes in biological communities which had varying traits and roles in reef ecosystem functioning and were differentially affected by the bleaching event. Understanding the impacts of bleaching on fish and cryptic communities will contribute to a better knowledge about the vulnerability of species and communities, as well as the resilience of coral reefs to bleaching events, and, ultimately, guide management measures.

Coral Larvae Connectivity Modeling in the Arabian/Persian Gulf Cavalcante, G.; Viera, F.; Mortenson, J.; BenHamadou, R.; Range, P.; Goergen, E.; Riegl, B. The Arabian/Persian Gulf was until recently home to rich coral reef communities that are now being degraded by both human and natural disturbances. Many studies examined the impact of environmental changes on coral communities, especially the effects of climate extreme events. A critical component for understanding degradation and recovery pathways, coral larvae transport and associated connectivity patterns within the Gulf remain largely unknown. Here, coral larvae transport among the Gulf’s coral communities is investigated with a high-resolution three-dimensional model (MIKE 3D FM) coupled with MIKE Agent Based Modeling (ABM) tool. In each simulation, modelled particles representing coral reef larvae were released into the hydrodynamic conditions present during the coral peak spawning period of April 2016. A subsequent 45 days (24 April – 10 June) run was allowed after release of particles from a total of 50 coral reef source areas. The hydrodynamic model reveals the typical circulation features for the period of study and is well correlated with other models over the Gulf. Preliminary results show that particles released from source areas located in the reefs near the Iranian coast can disperse long distances pushed by the anti-clockwise circulation, and can reach the southern Gulf. On the other hand, the lagrangian particle-tracking along Abu Dhabi and east Qatar coast suggests a more localized source of larvae seeding the reefs. This pattern could be corrected with the weak along-shore current speed.

Reef fish communities in the Red Sea Coker, D.J.; Kattan, A.; Carvalho S.; Berumen, M.L. The Red Sea supports high biodiversity and endemism, where approximately 10% of reef fishes are unique to this region. Documenting fish communities through surveys and collections over spatial and temporal scales is key to understanding changes of biodiversity across environmental gradients, habitats, or predict future trajectories in response to local and global stressors. However, as with many taxa in this region, historical data is lacking and fish communities are potential already compromised in some regions through climate change and local fishing pressure. In addition, the absence of marine protected areas, limited fisheries management, and the projected increase in pressure on Red Sea reefs through the expansion of aquaculture, tourism, and coastal development will further impact fish populations. Here I will present the main outcomes from a coral reef fish biodiversity program in the Red Sea that has spanned the latitudinal length of the Red Sea basin. This program, has generated the most comprehensive dataset in the region covering over 100 reefs and provides a large scale assessment of the region and a basis to answer fundamental ecological questions in marine spatial planning, conservation, and ecosystem function and services.

Life history impacts for coral reef fishes living in an extreme environment D’Agostino, D.; Burt, J.; Reader, T.; Fowler A.; Vaughan, G.; Cavalcante, G.; Santinelli, V.; Feary, D.

Determining the life history consequences for fishes living in extreme and variable environments will be vital in quantifying the potential impacts of climate change on coral reef fish demography. Using otolith sclerochronology, we compare and contrast population size-at-age and maximum size of Lutjanus ehrenbergii and Pomacanthus maculosus across the Arabian Gulf (‘Gulf’) and adjacent Gulf of Oman (‘Oman’). Furthermore, we use a mixed modelling approach to relate inter-annual growth variation to water temperature, salinity and productivity. Otolith chronologies provided a continuous record of growth over a 14- and 34-year period for L. ehrenbergii and P. maculosus, respectively. Individuals of both species showed smaller size at age and lower maximum size in the Gulf compared with conspecifics in Oman. Interestingly, salinity was the best environmental predictor of fish growth, with low growth corresponding to high salinity for both species. However, an interaction between spikes in chlorophyll-a levels with spikes in salinity levels strongly negatively affected growth in Oman P. maculosus populations, though had little effect on Gulf populations. We argue that within Gulf populations of both species, lower growth is associated with high osmoregulatory stress, while there is less impact of salinity variance on growth, suggesting potential local adaptation to the Gulfs highly variable environment. Our results highlight the value of understanding the drivers of long-term growth variation in coral reef fishes, and the role of an extreme environment in predicting of future demography impacts under a range of environmental scenarios.

Genomic approaches to track and monitor marine biodiversity on Arabian coral reefs DiBattista, J.D.; Bunce, M.; Berumen, M.L.; Priest, M.A.; Coker, D.J.; Sinclair-Taylor, T.H.; Hay, A.; Goatley, C.H.R.; De Brauwer, M.; Marshell, A. Biodiversity plays a critical role in the resilience of natural systems, and there is a directed effort towards understanding current threats to biodiversity (e.g. climate change). The emerging field of environmental DNA (eDNA) is transforming our approach to how we assess biological diversity and ecosystem function. eDNA is used to describe DNA shed from secretory processes such as the sloughing of skin, scales, mucus, eggs, sperm, blood, or defecation, and can be used to provide a record of a species presence. When combined with recent advancements in next-generation sequencing (NGS) and bioinformatics, the diversity of organisms from environmental samples that contain mixtures of DNA signatures can be recovered. As such, eDNA metabarcoding can provide a wealth of information for studies of biodiversity, food web dynamics, diet analysis, and for environmental and invasive species monitoring. I will highlight our research based on the development and application of eDNA metabarcoding for studying marine biodiversity across spatial and temporal scales in coral reef ecosystems. I will particularly focus on results obtained from Omani coral reefs as part of a collaboration between the Australian Museum and Sultan Qaboos University. I additionally highlight how these eDNA advances might be incorporated into existing or new marine monitoring programs in the UAE that aim to protect oceanic resources.

The demography of Red Sea reef fishes since the Last Glacial Maximum Emms, M.; Maisano-Delser, P.; Yang, Y.; Gurevich, T.; Li, C.; Kiflawi, M.; Manica, A. Mass mortality resulting from climate change-induced coral bleaching has been shown to reduce biodiversity and abundance, but our understanding of the effect of habitat loss and fragmentation on coral reef fishes is still limited. The Red Sea provides an ideal model system to disentangle local demography from the effect of migration, as its basin is enclosed with only one connection to the Indian Ocean via the narrow Bab el Mandeb strait in the south. During the Last Glacial Maximum approximately 20,000 years ago, low sea levels left the Red Sea effectively isolated and developing saline conditions, with coral reef fishes likely only persisting in refugia. This study investigates the complex demographic histories of reef fishes in the model Red Sea system, covering a period of extreme environmental change. We sequenced ~10,000 autosomal loci scattered across the genome in two species using a Targeted Gene Capture (TGC) approach which generated an unprecedented large and robust dataset for non-model coral reef fishes. Such a dataset provides a comprehensive assessment of their genetic diversity and allows the reconstruction of their demographic histories using Approximate Bayesian Computation (ABC) methods. Moreover, we also estimate key demographic parameters such as the growth rate of a recovering population and the minimum effective population sizes capable of recovery. For the first time, the combination of TGC and ABC methods used in this study provides a high resolution picture of the effects of habitat loss and fragmentation in coral reef fishes in the Red Sea.

Temporal structure of fish communities throughout the Arabian Peninsula Feary, D, Burt J, Berumen M, Bauman A We examine the composition and functional structure of coral reef fish communities within the Arabian Gulf, Gulf of Oman and Red Sea utilising historical and contemporary records of reef fish surveys. We then compare whether changes in the structure and function of fish communities mirrors published changes in live coral communities.

Symbiotic micro-algae and Green Fluorescent Protein (GFP) in Porites and Acropora off Kish Island, Persian Gulf Ghavam Mostafavi, P.; Kaveh Baghbadorani, Sh. Reef-building corals in the Persian Gulf have experienced a severe bleaching in summer 2017. Despite the mortality of most coral species in the northern islands, some of which including Acropora and Porites survived in the western part of Kish Island. This study examines the endosymbionts as well as Green Fluorescent Protein (GFP) of two species of corals in two different depths in winter and summer 2018. For this purpose, two coral species (3 different colonies, 3 replicates per each) were collected from the depth of 7.5 and 14 meters in western part of the Island. After RNA and DNA extraction, endosymbionts have been identified using real-time PCR and specific primers for Symbiodinacea. The GFP concentration was determined using real-time PCR. The results showed that Acropora in 7.5 meter harbored Durusdinium (formerly clade D), while in 14 meter it hosted both Cladocopium (formerly clade C) and Durusdinium, also Porites compressa had Cladocopium in shallow waters and Durusdinium and Cladocopium in 14 meter. The Q-PCR analysis revealed that the expression of GFP in summer is less than winter, a situation which is related to coral health.

Marine heatwaves reveal coral reef zones susceptible to bleaching Genevier, Lily G. C.; Jamil, Tahira; Raitsos, Dionysios E.; Krokos, George; Hoteit, Ibrahim As the Earth’s temperature continues to rise, coral bleaching events become more frequent. Some of the most affected reef ecosystems are located in poorly-monitored waters, and thus, the extent of the damage is unknown. Red Sea corals are exceptionally heat-resistant, yet bleaching events have increased in frequency. By tuning marine heatwaves (MHWs) to coral bleaching conditions, we created an atlas of MHWs over the data-poor Red Sea region, revealing hotspots of reef zones susceptible to bleaching. We found that: 1) if tuned to a specific set of conditions, MHWs identify all areas where coral bleaching has previously been reported; 2) those conditions extended farther and occurred more often than bleaching was reported; and 3) an emergent pattern of extreme warming events is evident in the northern Red Sea (since 1998), a region until now thought to be a thermal refuge for corals. We argue that bleaching in the Red Sea may be vastly underrepresented. Additionally, although northern Red Sea corals exhibit remarkably high thermal resistance, the rapidly rising incidence of MHWs of high intensity indicates this region may not remain a thermal refuge much longer. As our regionally-tuned MHW algorithm was capable of isolating all extreme warming events that have led to documented coral bleaching in the Red Sea, we propose that this approach could be used to reveal bleaching-prone regions in other data-limited tropical regions. It may thus prove a highly valuable tool for policy-makers to optimise the sustainable management of coastal economic zones.

Corals respond to the hottest reefs through symbiont fidelity not flexibility Howells, E; Bauman, A; Vaughan, G; Hume, B; Voolstra, C; Burt, J While some corals can enhance their thermal limits by associating with dinoflagellate photosymbionts of superior stress tolerance, the extent to which these symbiont communities will reorganise under global warming remains unclear. Here we show, that in the hottest reefs in the world, corals maintain associations with the same symbionts despite extreme seasonal warming and acute heat stress (≥ 35°C). In the Oman Sea, all corals associated with Durusdinium (clade D) and only a minority hosted background levels of Cladocopium (clade C). In contrast, in the more thermally extreme Arabian/Persian Gulf, corals predominantly associated with Cladocopium and most also hosted Symbiodinium (clade A) and/or Durusdinium. During acute heat stress, the higher prevalence of Symbiodinium and Durusdinium in bleached versus non-bleached Gulf corals indicates that these background genera did not confer bleaching resistance. Within symbiont genera, the majority of ITS2 type profiles were unique to their coral species, confirming the existence of host-specific symbiont lineages. Notably, further differentiation among sites demonstrates that symbiont populations are either isolated or specialised over 10s-100s of km. Thermal tolerance across coral species was linked to the prevalence of a single ITS2 intragenomic sequence variant (C3gulf) definitive of the C. thermophilum group. The abundance of C3gulf was highest in bleaching resistant corals and at warmer sites, suggesting a potential functional role in resilience that warrants further investigation. Together, our findings indicate that co-evolution of host-Symbiodiniaceae partnerships favours fidelity rather than flexibility in extreme environments and under future warming.

The hidden fishes of UAE: cryptobenthic fish compositions in thermally extreme coral reefs Johansen, J, SJ Brandl, J Casey, L Tornabene, J Burt The Arabian Gulf (AG) reefs are the thermally most extreme reefs on Earth. These reefs are typically thought to be comprised of low species diversity but high abundance of a few single species. However, all previous species composition analyses have relied on visual surveys across reef-scapes. Here we present the first examination of the cryptic fish species composition that exists within the reef matrix of AG coral reefs, including putative new species for the region.

Macrofaunal and microbial communities associated with sponges in the central Red Sea Kandler, N.; Wooster, M.; Leray, M.; Michell, C.; Knowlton, N.; de Voogd, N.; Paulay, G.; Voolstra, C.; Berumen, M. Sponges act as important microhabitats and promote biodiversity by harboring a wide variety of macrofauna and microbiota, but little is known about the magnitude and diversity of sponge symbionts and the relationships between them. This study uses DNA barcoding to examine the macrofaunal and bacterial communities associated with sponges of the central Saudi Arabian Red Sea, an understudied ecosystem with high biodiversity and endemism. In total, 185 epifaunal and infaunal and 2814 bacterial operational taxonomic units (OTUs) were distinguished from 129 sponges representing seven sponge species, one of which (Stylissa carteri) was intensively studied. A significant difference was found in the macrofaunal community composition of S. carteri along a cross-shelf gradient, with more amphipods associated with offshore sponges and more brittle stars and fishes associated with inshore sponges. Abundance of S. carteri increased with proximity to shore, but bacterial community composition remained consistent across all sampling locations. Both macrofaunal and bacterial community compositions differed significantly between several sponge species sampled from one location. Four of the seven sponge species collected were dominated by a single annelid OTU, which was unique to that sponge species. A fifth was dominated by four arthropod OTUs, all species-specific as well. There was a correlation between macrofaunal and bacterial diversities, with the latter higher in the four annelid-dominated sponge species. As environmental change continues to impact coral reef ecosystems, understanding the ecology of sponges and their role as microhabitats, particularly in extreme environments, may become more important for understanding their full ramifications for biodiversity.

Genome-wide investigation of adaptation in a sea urchin from the world’s warmest reefs Ketchum, R.N.; Edward G. Smith; Melissa B. DeBiasse; Joseph F. Ryan; Grace O. Vaughan; Dain McParland; Noura Al-Mansoori; John A. Burt; Adam M. Reitzel Climate change has resulted in warming of coastal aquatic habitats around the world at almost every latitude, threatening ecosystems with a significant loss in biodiversity and potential collapse. Genomic analyses of species currently living in naturally extreme environments can help identify how populations will persist through future climate change through identifying candidate genomic regions that may be targets of natural selection. Understanding the genomic response to climate change is especially important in keystone species, where the impacts of a changing environment could have far reaching consequences. Sea urchins of the genus Echinometra are keystone herbivores found across the Indo-Pacific and play a significant role in the health and dynamics of coral reef ecosystems as grazers and bioeroders. We set out to investigate population dynamics and targets of selection in Echinometra sp. EZ, through restriction site- associated DNA sequencing and draft genome assembly. We collected from seven populations in the Gulf of Oman (summer maxima ~30-32°C) and the neighboring thermally-extreme Persian/Arabian Gulf (summer maxima ~35-37°C). Population genetic analyses identified the presence of two populations (Structure; K=2), each associated with either Gulf, although population structure was weak (FST=0.006). Interestingly, outlier analysis identified genes under selection involved in transcription regulation and methylation. The results generated from this study will provide crucial data on a keystone species experiencing extreme environmental conditions and fill a critical knowledge gap by providing genomic insights into how species will respond to climate change.

Intergenerational epigenetic inheritance in reef-building corals from the Arabian Gulf Liew, Y.J.; Howells, E.; Wang, X. ; Michell, C.T.; Burt, J.; Idaghdour, Y.; Aranda. M. The perception that the inheritance of phenotypic traits operates solely through genetic means is slowly being eroded: epigenetic mechanisms have been shown to induce heritable changes in gene activity in plants and metazoans. Inheritance of DNA methylation patterns provides a potential pathway for environmentally induced phenotypes to contribute to evolution of species and populations. However, in basal metazoans, it is unknown whether inheritance of CpG methylation patterns occurs across the genome (as in plants) or as rare exceptions (as in mammals). Here, we show that DNA methylation patterns in a reef-building coral are determined by genotype, developmental stage, as well as by parental environment. Transmission of CpG methylation from adults to their sperm and larvae demonstrates genome-wide inheritance. Variation in the hypermethylation of genes in adult corals and their sperm from inside and outside the Arabian Gulf, indicates intergenerational acclimatisation to local temperature and salinity. Furthermore, genotype-independent adjustments of methylation levels in stress-related genes were strongly correlated with offspring survival rates under heat stress. These findings support a role of DNA methylation in the intergenerational inheritance of traits in corals, which could extend to enhancing their capacity to adapt to climate change.

Decadal changes in the Gulf of Oman’s coral reef communities Marshell, A.; Halford, A.R.; Burt, J.A.; Priest, M.A.; McIlwain, J.L. The Sultanate of Oman’s coral reef communities support more than 120 coral and 580 fish species, patchily distributed across coastline adjacent to the Gulf of Oman and Arabian Sea. They exist in a unique biogeographic setting and support one of the largest fisheries economies in the region, yet they remain understudied. Here, we present observed differences in the Gulf of Oman’s coral reefs and associated fish communities from complementary surveys conducted 13 years apart. Observed changes are discussed in the context of known disturbances that have occurred during this period and provide insights into the likely resilience of these systems to future environmental conditions. Musandam (15 sites) and Muscat (9 sites) reefs were surveyed to quantify fish and benthic communities in 2004, and again in 2017. At each site, three 50 x 5 m transects were conducted at 6 - 10 m deep, and all fish species belonging to the nine most common coral reef-associated families were counted in 2004 and 2017 by the same observer (ARH). Benthic community photos were analysed using Coral Point Count software (51 substrate categories). In comparison to many other coral reef communities, Oman’s reefs are still relatively healthy overall, but are significantly impacted and remain threatened by many increasing local (e.g., overfishing, pollution, predatory starfish outbreaks, and unsustainable development), and global stressors (e.g., warming temperatures, oxygen depletion, cyclone damage, harmful algal blooms). Long-term monitoring of coral reef communities is vital to understanding their response to increasing disturbances, and foundational to the development of effective management plans for sustaining the health of Oman’s unique coral reef communities.

Lessons from fine-scale resolutions of coral-algal associations in the Central Red Sea Mejia-Restrepo, A.; Hume, B. C. C.; Voolstra, C. R.; Berumen, M. Recent advances in genotyping the algal component of the coral holobiont should make us question and recontextualise what we know about coral-algal associations. Specifically, we should readdress to what degree each algal genotype is specialised to a given set of abiotic or biotic factors, what propensity the coral host has for modulating their algal complement, and at what level algal phenotypes map to genotypic resolutions. Contrary to common perception, our understanding of these topics is far from complete and contemporary analyses often contradict long-standing beliefs on the topic. Nowhere is the critical reassessment of these resolutions more pertinent than in the world’s most extreme coral habitats that are increasingly being used to better understand the continued degradation of our planets reefs. Here, using the SymPortal framework to perform a fine scale analysis of the ITS2 marker, I present an investigation of over 600 coral-algal associations across six species of scleractinian coral and one calcifying hydrozoan. I will present on the results of a Summer and Winter sampling, across six reefs spanning an inshore-offshore gradient with multiple depths sampled at each site. I will use the results from this study to a) demonstrate that resolution matters and to b) perpetuate the contemporary hypothesis that the majority of host-algal associations are specialised and that host-generalist ‘stress resilient’ taxa represent a small proportion of overall genotypic diversity.

Some like it hot! How Arabian Gulf reef fishes survive thermal extremes Mitchell, M.D.; Vaughan, G.O.; Johansen, J.L.; Burt, J.A. As ectothermic species the physiological and physical performance of coral reef fishes is determined by the ambient temperature of their environment. With global temperatures predicted to increase due to climate change there is a need to understand how fishes will respond to temperatures that exceed those they currently experience. The Arabian Gulf offers an ideal system to explore how coral reef fishes have responded to extreme thermal environments, as its With coral reefs currently exist in a thermally extreme environment that includes temperatures predicted under climate change. To test how fish have responded to thermal stress, we compared the swimming performance and metabolic performance of two fish species (Lutjanus ehrenbergii and Scolopsis ghanam) with population in the Arabian Gulf (AG) and Gulf of Oman (GO), across the full range of seasonal temperatures (18, 22, 27, 31.5 and 35.5oC). Temperatures represented winter minimums (AG-18oC, GO-22oC) annual mean (both 27oC) and summer maximums (AG-35.5oC, GO-31.5oC). Fish were collected at each temperature and measured for their maximum swimming performance (Ucrit), gait-transition speed (Up-c), resting metabolic rate (MO2-rest), maximum metabolic rate (MO2-max) and aerobic scope (Asc). For both species from both locations performance in all measures decreased at both winter and summer maximums relative to mid-season temperatures. The relative performance of GO fish to AG fish at AG winter and summer temperatures suggests that fishes of the AG have adjusted to the thermal environment of the AG through mechanisms associated with both acclimation and adaptation.

Geophysical features of the Red Sea create coral refugia from ocean warming Monroe, A.A.; Genevier, L.; Coker, D.J.; Raitsos, D.E.; Hardenstine, R.S.; Hoteit, I.; Berumen, M.L. Mass coral bleaching occurred on coral reefs around the world from 2014-2016 following a record El Niño event. Many areas that rarely experience coral bleaching, such as the Red Sea, were affected by anomalously high sea surface temperatures (SST). Despite their presumed high thermal tolerance many coral reefs in the Saudi Arabian Red Sea bleached, most for the first time since 1998. In the south central Red Sea (~19N), a severe marine heatwave in 2015 led to high rates of bleaching-related coral mortality on Saudi Arabian reefs (~60%), while on the opposite coast (Sudan) limited bleaching followed by 0% coral mortality was observed. To understand this discrepancy of bleaching-related mortality between reefs at similar latitudes, we analyzed the physical characteristics of the two regions using high-resolution satellite and modeled data. SST data revealed the marine heatwave over the Sudanese coast was ~1C lower than the Saudi Arabian coast. Conversely, wind speed was much stronger over Sudan due to the Tokar Jet: a phenomenon caused by a gap in the Sudanese mountains (~14) that channels summer monsoonal winds over the Red Sea. Moreover, anomalously low wind speeds coincided with severe bleaching on the eastern coast. As these spatial patterns are also present in the climatologies, we propose that the Tokar Jet has created a coral refugium from ocean warming for coral reefs in the southwestern Red Sea through evaporative cooling. However, changes in monsoonal winds as well as continued ocean warming could disrupt this phenomenon, leaving these corals unprotected.

Diversity of Symbiotic Micro-algae Associated with Zoantharians Species in the Persian Gulf Noori Koupaei, A; Dehghani, H; Mostafavi, P.G. Members of the order Zoantharia are conspicuous inhabitants of tropical marine ecosystems. They generally inhabit substrates of intertidal zones and coral reefs. Most of the zoantharians, like numerous other coral reef inhibiting invertebrates, host a group of endosymbiotic dinoflagellates in the family Symbiodiniaceae. The physiological characteristics of symbiodinian-hosting organisms may be adapted to their environment according to the genus of symbiont hosted. Hence identification of symbiont plays a crucial part in understanding of the ecology and biogeography of the holobiont. Zoantharians are commonplace in the Persian Gulf (PG), experience periods of anomalous high temperature, irradiance and desiccation. Their survival largely relies on the symbiotic relationship. However, the phylogeny of symbionts of zoantharians has not been investigated in the region. In this study, the second internal transcribed spacer region of ribosomal DNA (ITS2) was used to recognize in hospite populations of Symbiodiniaceae in Zoanthus sansibaricus (n=18), Palythoa aff. mutuki (n= 9) and Palythoa tuberculosa (n=3) colonies from Hengam, Kish, Larak, and Qeshm Islands, in the PG. The results showed Durusdinium trenchi D1-4 and Symbiodinium A1, were the most prevalent endosymbionts. Symbiodinium appears to be adapted to stressful environmental conditions by producing substantial amounts of mycosporine-like amino acids (MAAs), compounds which provided strong protection against UV radiation. The synthesis of MAAs is speculated to be an adaptive responsive strategy to anomalies of high light intensities. Predominance of stress tolerant Durusdinium trenchi and putatively radiation tolerant Symbiodinium in zoantharian species might suggest an adaptation strategy to the extreme physical environment of the PG.

Observation of host-symbiont specificity in four scleractinians in the northern ROPME Sea Area Oladi, M., Shokri, M.R., Rajabi-Maham, H. Reef-building corals are in obligate symbiosis with dinoflagellates of the family Symbiodiniaceae. Each lineage of these remarkably diverse endosymbionts provide the host with differential tolerances to survive over a range of environmental conditions. Therefore, identification of these unicellular algae may be used as a tool to assess sensitivity or resistance of corals in a water body and set conservation priorities. Unfortunately, the true diversity of these microalgal endosymbionts and patterns of their interactions with different host taxa remains poorly characterized in the northern waters of the ROPME Sea Area. In this contribution, the dominant Symbiodiniaceae in association with the scleractinian corals Acropora sp., Porites harrisoni, Dipsastraea sp. and Stylophora pistillata were analyzed for genotyping (using the internal transcribed spacer region 2) in Qeshm Island (northern Persian Gulf) and Chabahar Bay (northern Gulf of Oman). Within the four host genera examined, four genetically distinct symbiont types (two in Cladocopium, one in Symbiodnium, and one in Durusdinium) were distinguished. Each ITS2-type symbiont was associated with a particular coral species, most of which were previously reported from the area, except for Cladocopium-C39 that inhabited Dipsastraea sp. in Chabahar Bay. Predominance of a host-generalist symbiont usually occurs in places with relatively stable environmental conditions. Accordingly, observation of rather high levels of host-symbiont specificity in the harsh environment of the northern inner ROPME Sea Area is not surprising, as these stable partnerships are considered beneficial to these corals.

Coral microbiome composition in the northern Red Sea suggests high plasticity of bacterial communities Osman, E.O; Suggett, D.J.; Voolstra, C.R.; Pettay, T.D.; Clark, D.R.; Pogoreutz, C.; Sampayo, E.M.; Warner, M.E; Smith, D.J. The capacity of reef-building corals to tolerate heat stress is a key factor determining their persistence under future climate change. The flexibility of coral microbiome is a potential mechanism that may assist corals to mitigate environmental stressors. Interestingly, corals in the northern Red Sea tolerate extreme thermal anomalies (up to 15 DHWs), however the composition of the coral microbiome and how it contributes in acclimatization process in this region is entirely unknown. This study aimed to identify whether acclimatization to local thermal regimes was accompanied by specific differences in the coral microbiome. We investigated the microbiome (endosymbiont and bacteria of surface mucus layer - SML) of six coral species from five sites spanning 4˚ of latitude and representing thermal gradient in the northern Red Sea. A total of 19 distinct dinoflagellate endosymbionts were identified belonging to three genera (Symbiodinium-13%, Cladocopium-86% and Durusdinium-1%), with notably five novel types (19%). The endosymbiont community showed a high degree of host-specificity despite the latitudinal temperature gradient. In contrast, the composition of the SML bacterial communities varied significantly between sites aligned with thermal gradient, however it was also coral species-specific. This study highlights selection of certain endosymbiont genotypes (or genetic adaptation) within the region, however host-specificity may demonstrate physiological plasticity in different thermal regimes. In contrast, the dynamic composition of the SML at different sites/temperatures may affect the functional response of the coral holobiont and thus broaden the fundamental niche. Therefore, the SML bacterial communities may aid the holobiont local acclimatization by readily responding to environmental changes.

Strong correlation between microbal and metabolic diversity in Acropora sp. corals and disease outbreaks Ochsenkuehn, M; Howells, E.; Abrego, D.; Burt, J.; Amin, S. Coral holobionts depend on specific microbiome compositions for environmental stress and disease resilience. Environmental stressors, such as extreme temperatures, often lead to changes in the associated microbiome and therefore increased susceptibility to disease. Associated microbes may enhance the chemical potential of the holobiont and in consequence increase stress and disease resilience. However, no direct correlation between coral metabolite diversity and the microbial community has been proven. Here we examine the relationship between microbial and metabolite diversity of Acropora species as a function of temperature and the influence recurring disease has on these factors. We monitored and sampled healthy and white syndrome infected Acropora sp. colonies over 2 years across a range of temperature extremes (<25˚C and >34˚C at 42 PSU) at Saadiyat Reef, Abu Dhabi, UAE. Samples were analysed for microbal composition (prokaryotes, phytoplankton and fungi) and metabolite diversity. Our results show that the metabolite diversity of Acropora correlates with the summer-winter temperature cycle. Moderate (26-28 ˚C) temperatures indicated a non-stressed phenotype with high chemical diversity, whereas high (up to 35 ˚C) and low temperatures (24 ˚C) both showed decreased metabolite diversity and abundance suggesting a stressed phenotype. The microbial composition of the holobiont community also showed strong temperature correlations, similar to the metabolite profiles. This loss in the chemical and microbial diversity at extreme temperatures likely leads to the proliferation of invasive microbiomes and therefore an increase in pathogenicity.

Role of Summer Winds in Modulating Coral Bleaching in the Persian/Arabian Gulf Paparella, F; Burt, J.; Xu, C.; Vaughan, G.; Al Mansoori, N. Warming sea temperatures associated with climate change have resulted in numerous coral bleaching events in the Gulf since the mid-1990s, but it has been unclear why unusually warm sea temperatures occur some years but not others. Using a combination of observed sea-bottom temperatures at three reef sites and a meteorologically-linked hydrodynamic model that extends through the past decade, we show that summer sea-bottom temperatures are tightly linked to regional wind regimes, and that strong ‘shamal’ wind events control the occurrence and severity of bleaching. Sea bottom temperatures are primarily controlled by latent heat flux from wind-driven surface evaporation which exceeds 300 W/m^2 during shamal winds, double that of typical breeze conditions. Using observed and simulated data from 2012 to 2017, we show that years with reported bleaching events (2012, 2017) were characterized by low winds speeds that resulted in temperatures persisting above coral bleaching threshold temperatures for >5 weeks, while the cooler intervening years (2013-2016) had summers with more frequent and/or strong shamal events which repeatedly cooled temperatures below bleaching thresholds for days to weeks. We show that winds of 4 m/s represents a critical threshold for whether or not corals cross bleaching threshold temperatures, and provide simulations to forecast sea-bottom temperature change and recovery times under a range of wind conditions. The role that wind-driven cooling may play on coral reefs globally is discussed.

High-resolution Sea Surface Temperature Reconstructions from Abu Dhabi Corals Retrum, J.B., Gifford, J. N.; Burt, J. A. The United Arab Emirates coral reefs have experienced significant decline from coastal development and increasing sea surface temperatures (SST) during the last century. To better understand the impact of SST on coral degradation, one living Porites sp. was harvested and nine recently dead corals were cored from a reef near Saadiyat Island, and a Porites sp. fragment was collected from an archaeological site. High- resolution geochemical analyses were conducted on the living Porites sp., measuring 18.5 cm with ~7 annual bands, a Porites sp. core, measuring 31.1 cm in length with a minimum of 37 annual bands, and the archaeological fragment, preserving one annual band. The recently dead and archaeological Porites sp. were dated using U/Th disequilibrium. All samples were subsampled at 0.5-mm or 1-mm intervals for stable isotope, 18O and 13C, and trace element, calcium and strontium, geochemical analyses. Preliminary results from the modern corals indicate summer 18O values range from -3.0 to -4.1‰ corresponding to ẟ ẟ SST of 33 to 35℃ and winter 18O values range from -1.2 to -2.5‰ corresponding to SST of 20 to 22℃. ẟ A temperature calibration curve for 18O and instrumental SST was constructed to calculate the ẟ archaeological coral SST range. The archaeological coral, dated to 1805 ± 2 AD, exhibited 18O values ẟ ranging from -1.6 to -3.1‰, corresponding to a SST range of 20 to 29℃. SST reconstructions using only ẟ 18O values are influenced by salinity. Trace element geochemical analyses are currently being run to remove salinity from the current temperature calibration curve. ẟ Population dynamics of Gulf reef corals in response to natural and man-made disturbances Riegl, B.; Johnston, M; Cavalcante, G. Repetitive coral mass mortality is increasingly common across the world. Driven by proximal (environmental changes) or distal (societal) factors, it can upset established communities, leading to species-loss and altered communities. The Arabian Gulf is a reef environment with a subset of Indo-Pacific species, plus endemics, that is frequently disturbed, both by distal and proximal drivers and the severity of these impacts is constantly increasing. Coral reef loss, particularly in the southern Gulf, has considerably increased over the past decade and in many areas, coral reefs must now be considered critically endangered. Many formally reef-rich areas are now completely devoid of such ecosystems. Local heating correlates with changes in coral population dynamics and community structure and leads to discrete population events (mortality and altered life-dynamics) that alternate with undisturbed dynamics. Climate-driven degradation will be hard to manage, but natural adaptation will occur. 25 years of monitoring led to the definition of three phases of coral population dynamics in response to the environment (least disturbed LD pre-1996; medium disturbed MD 1998-2010 and 2013-17, disturbed D 1996/8, 2010/11/12, 2017/18) with three theoretical stable states of declining coral frequency and cover. Increased disturbance leads to progressive reduction in coral size, cover, and population fecundity. More disturbance increases connectivity requirements in metapopulations. Metapopulation models suggest better recovery in species experiencing partial rather than whole-colony mortality. Connectivity required to avoid extinction increases exponentially with linear increase in disturbance frequency and its correlation across the metapopulation. Variable extinction thresholds exist across communities that determine which species will be winnowed out and which will maintain acceptable population levels. Besides projected changes in coral community and population structure, no species are projected to increase, highlighting the endangered nature of these iconic ecosystems. The expected higher disturbance frequency will lead to net loss of coral cover and novel community arrangements in the Arabian Gulf. Acropora dominated on many reefs since the Pleistocene, but no longer does. Other common species (Porites harrisoni, Dipsastrea pallida, Platygyra daedalea) also declined and disappeared from some areas, but recovered in others. A degradation sequence in order of species loss exists: Acropora to Porites and/or Platygyra to Dipsastrea to Cyphastrea.

Home range and territorial behaviour of some common grouper species (Epinephelinae) in Northern Red Sea Saleh, B.M., Mohammed M. Abozeid, Ashraf I. Ahmed, Magdy A. Alwany, M. El-Sherbiny Determining the territories of coral reef fishes is a prerequisite to identifying their behavior and the space occupied by each fish, especially predator ones. This study described the movement pattern and determined the territories surface areas for five grouper species in the Northern Red Sea. Where three of the five species were first to undergo a study of this type in the region, the other two species C. miniata and C. hemistiktos have already been scrutinized in the gulf of Aqaba by Shpigel and Fishelson. In the present study the C. miniata found to be the only polygamous grouper, living in social units composed of 4 to 6 individuals. On the other hand, C. hemistiktos has been classified as monogamous and each social unit is composed of two individuals. A. rogaa and V. loti, are monogamous and only one species E. fasciatus live solitary.The territories surface areas were measured for the five species regardless of their sex as follows: V. loti 1514.62 m2 A. rogaa 324.69 m2, E. fasciatus 208.12 m2, C. miniata129.17 m2 and C. hemistiktos 24.4 m2. A significant relationship was detected between body size of groupers and territories sizes. Generally, male territory sizes are bigger than that of females. Another significant regression relationship was found between the total length and the territory size of Male C. miniata, C. hemistiktos and A, rogaa (R2ranging between 0.945 to 0.992). The other two species however, had not undergone the same male and female comparison, as a result of the difficulty to catch the targeted individuals of V. loti for the purpose of sex determination. While all of the studied samples of E. fasciatus was females, both species on the other hand (regardless of the sex), exhibited a significant regression relationship between body size and territories size.

Exploring strategies to increase thermal resilience of corals in Saudi Arabian waters Schmidt-Roach, S.; Muniz Baretto, M.; Cziesielski, M.; Herrera Sarrias, M.; Prasanna, A.; Aranda, M.

The desert seas of Saudi Arabia are home to some of the warmest coral reefs in the world. While corals in the Northern Red Sea experience mean monthly summer maximum temperatures around 27°C, the Southern Red Sea is regularly exceeding 32°C, the Arabian Gulf 34°C. We sampled seven locations across a latitudinal gradient along the Red Sea coast as well as one reef in the Arabian Gulf aiming to elucidate the evolutionary history and connectivity of these populations. Collected individuals included survivors of the 2015/2016 mass bleaching event, which severely impacted the visited reefs in the Southern Red Sea and the Gulf. ITS2 amplicon sequencing of the algal symbiont populations showed a latitudinal shift from Cladocopium taxa in the North to Durusdinium taxa in the Southern Red Sea, whereas the Gulf corals were either associated with Cladocopium thermophilum or Symbiodinium species. ezRAD sequencing of the coral colonies correlates with these findings, showing the highest structural divergence for the Southern Red Sea and the Gulf. To elucidate potentials for assisted gene flow via transplantation we conducted a common garden experiment in the Central Red Sea and investigated how individuals from these populations differ in thermal tolerance and survival. During the summer temperature peaks, bleaching was exclusively observed for individuals from the Northern Red Sea that also showed the highest mortality. However, the mean survival rate was highest for local individuals, stressing the importance of local adaptation. High mortality rates, especially of the Arabian Gulf individuals, strongly suggests that translocation across diverse habitats may have uncertain success.

Relationship between bioerosion rate of corals with skeletal density and water depth Seyfabadi, J, Hamed Mashhadi, Hamid Rezaei The relationship between skeletal density and depth (2, 5 and 9 meters) on the bioerosion rate of two coral genera Platygyra and Porites was investigated. For this purpose, 5 coral pieces of each genus from Larak Island were cut in the direction of the tallest central axis with a thickness of about 7 mm and their photos were taken. The bioeroded area was evaluated by ImageJ 1.44 software. Freezing method was used to measure the skeletal density. The results showed that increase in depth was associated with significant increase in the bioerosion rate of Platygyra. Also, increased skeletal density showed a positive and significant correlation with bioerosion in Platygyra, but not significant in Porites. This indicates that some bioeroders prefer denser corals for various reasons. Denser corals also appear to be less capable of rebuilding their dead colonies by tissue growth. In this way, a large part of the denser coral skeleton is more exposed to the bioerosion attack. Increased bioerosion rate in deeper water might be due the reduced availability of suitable substrate for bioeroders.

Rapid adaptive radiation of the thermally tolerant symbiont Cladocopium thermophilum Smith, EG; Hume, BCC; Ketchum, RN; McParland, D; Voolstra, CR; Burt, JA The endosymbiotic dinoflagellates of the genus Symbiodinium, play a critical role in the thermal tolerance of their coral host. Corals in the world’s warmest reefs, found in the Persian/Arabian Gulf (PAG), widely associate with Symbiodinium thermophilum, a recently described species that is adapted to the extreme thermal maxima (>34°C) found in the PAG. Using a novel ITS2 approach, we recently identified the presence of host-specific strains of S. thermophilum on a single reef from the southern PAG suggesting there is further unresolved diversity in this thermally tolerant symbiont. However, the diversity and degree of specificity in S. thermophilum populations from other reefs is largely unknown despite its potential to enhance our understanding of the evolutionary dynamics between these ecologically important symbionts and their coral hosts. Here, we investigate the diversity of S. thermophilum in four coral hosts (Acropora downingi, Cyphastrea microphthalma, Platygyra daedalea and Porites spp.) across six reefs in the northern, central and southern PAG. Using SymPortal analyses of ITS2, and the psbA non-coding region, we reveal that host-specific strains are common in S. thermophilum and that there are distinct S. thermophilum communities between different geographic locations. Considering that the modern shorelines of the PAG were only formed ~6,000 year ago, our results suggest that these ecologically specialised strains must have evolved rapidly to exploit the different hosts and local environmental conditions. These findings indicate that S. thermophilum represents a diverse and highly specialised lineage that has undergone rapid adaptive radiation and demonstrate the benefits of IGV-based ITS2 analyses.

Ten years of change in two coral areas in the Sea of Oman: cyclones, red tides, coral predation & patterns recovery Taylor, O.J.S., Benson, I.R., Looker, E.L., John, D.G. Coral communities in the Sea of Oman have experienced a number of significant events in recent years, that have had a profound effect with regards to the development and current status of those communities. These events have been linked to potential shifts in climate patterns (coral bleaching and cyclones), the introduction of potentially invasive species (red tides), as well as more widely recognised (but still relatively undocumented, regionally) impacts relating to crown of thorns starfish (COTS). This work presents two case studies that track shifts in coral communities over a twelve-year period: In the first, annual coral surveys at the Mirbah Reef on the eastern coast of Fujairah, highlight dramatic changes in coral cover and community structure since 2006; from a time when high, live coral cover (>80-90%) and structural heterogeneity was impacted, first by Cyclone Gonu (June 2007), followed by very high levels of mortality during the red tide of 2008, intermittent periods of COTS predation, and subsequently significant recovery. In the second, we present the findings of three survey periods, each covering forty locations within the Daymaniyat Islands Marine Protected Area in Oman. The study focuses on the immediate impacts of Cyclone Gonu (June 2007) on shallow water coral communities, which were surveyed immediately before and after the cyclone, followed by a re-survey of the same areas to determine recovery >10 years after the event.

Coral Reefs & Other Marine Habitats: A Marine Habitat Map of the Northern United Emirates Taylor, O.J.S., Matteos, D.M. We present the findings of a marine and coastal habitat mapping project undertaken in 2017- 2018 to support the current understanding and distribution of marine habitats in the northern United Arab Emirates (Sharjah, Ajman, Umm Al Quwain and Ras Al Khaimah). The study required the development of a hierarchical habitat classification scheme which included geoform and ecology based habitat classifications; the use of freely available Sentinel – 2 satellite imagery and algorithms to provide the basis for the production of supervised classification maps; supported by ground-truthing information developed through a stakeholder engagement process, incorporation of existing data, and extensive targeted field surveys. The primary purpose of the project was to determine areas of important habitats such as coral reefs which were not previously presented in a readily accessible form; allowing management decision- making which accounts for important areas of biodiversity or critical habitats. The secondary objective was to develop and share a cost-effective methodology for encouraging satellite-based mapping in the region, with the goal of furthering conservation and sustainable development objectives.

Adaptation to extreme thermal conditions; metabolic costs for fishes living on the world's hottest coral reefs Vaughan, GO; Johansen, JL; Mitchell, MD; McParland, D; Shiels, HA; Burt, JA Tropical coral reefs are predicted to be amongst those most impacted by climate change since they have evolved under relatively stable thermal conditions. It is suggested that many species may already be living close to their upper thermal limits, with little capacity to acclimate to further warming. Current maximum summer temperatures for the majority of coral reefs globally are 32oC, with an additional 3-4oC heating projected by 2100. However, the hottest coral reefs on Earth (Arabian Gulf, AG) are already experiencing summer maxima above 35oC and an annual thermal range >17oC, creating a present day example of ocean warming impacts. Here, we investigate how three species of coral reef fishes (Scolopsis ghanam, Cheilodipterus novemstriatus and Escenius pulcher) have managed to acclimate and/or adapt to extreme thermal conditions. We compared the metabolic performance across populations from the southern AG, to the thermally more benign Gulf of Oman (GO) reefs (annual temperature range 22-32oC), at five temperatures incorporating the existing AG thermal range (18, 22, 27, 31.5, 35.5oC). Fishes were collected throughout the year when SST matched that of experimental temperature, allowing an accurate representation of any natural acclimation. As conditions in the GO do not reach the same seasonal extremes, those fishes were acclimated for >3 weeks to 18oC and 35.5oC before experimental procedure. Maximum and resting oxygen consumption rates were measured for each species and population at each temperature, using static intermittent respirometry. Our results reveal that all three species from the AG displayed a shift in peak aerobic scope to higher temperatures than GO fishes, suggesting thermal adaptation or acclimation has occurred in order to meet metabolic demands at higher temperatures. However, all three species showed a significantly reduced aerobic scope at both the coolest and warmest temperatures, leaving little additional energy available for enhancing ecological activities. Resting metabolic rate increased exponentially from 18oC to 35.5oC in all species and populations, indicating the importance of maintaining performance to acquire food and fulfill energetic demand. This study indicates that although there may be capacity for some reef fish species to adapt to survive projected increases in SSTs and thermal fluctuations, this comes at the cost of severely reduced aerobic performance at both ends of the scale.

Unraveling biodiversity patterns of cryptic macroinvertebrate communities in the Red Sea Villalobos, R.; Aylagas, E.; Mejia-Restrepo, A.; Pearman, J.; Anlauf, H.; Roth, F.; Cúrdia, J.; Ellis, J.; Berumen, M.; Carvalho, S. Most of the biodiversity in coral reefs is attributed to small-sized cryptic species sheltered in crevices, associated with reef biological engineers and/or with exclusive nocturnal activity. These characteristics make the assessment through traditional visual surveys challenging, which has resulted in a very limited knowledge of this biological component of the reef. Considering the ongoing degradation of coral reefs worldwide, sound knowledge of how biodiversity patterns change across environmental gradients is, however, fundamental and urgent. In this presentation, I will show the results of a basin-wide study of the biodiversity of Red Sea cryptic macroinvertebrates (>2 mm) based on individual DNA barcoding of the mitochondrial cytochrome c oxidase I (COI) gene. A total of 54 Autonomous Reef Monitoring Structures (ARMS) deployed on 18 reefs along the Saudi Arabian coast of the Red Sea were analyzed. Biodiversity patterns were compared with changes in various potential environmental drivers such as: in situ temperature measurements (HOBO temperature loggers), sea surface satellite temperature, surface chlorophyll-a concentration, and percentage cover of benthic groups determined from photo-transect surveys. Our results show changes in the biodiversity patterns across the latitudinal scale of the Red Sea that reflect responses of cryptic macroinvertebrates to a combination of factors ranging from the composition of nearby communities to sea surface temperature, as well as biomass of primary producers. The current study will help in gaining a better understanding of the existence of potential biodiversity hotspots along the Red Sea as well as the processes driving the cryptobiome (i.e., if niche or dispersal- based).

Diagnosing temperature resilient reefs and genotypes in the Arabian Seas using a standardized portable coral bleaching system

Voolstra, C; Anny Cardenas; Gabriela Perna; Carol Buitrago-Lopez; Hannah Aichelmann; Maoz Fine; Daniel J Barshis Coral bleaching (i.e., the loss of Symbiodinium due to stress) is now the main driver of reef degradation and it is unclear whether the rate of ocean warming will exceed the adaptive capacity of corals and their symbionts. The common notion is that corals bleach and suffer mortality at just 1-2°C above their mean summer maxima, but we actually know little about empirical temperature thresholds, as most of our knowledge comes from predictive modeling, observational studies, or long-term thermal exposure experiments. In particular, corals from the Arabian Seas harbor extraordinarily high bleaching tolerance limits approaching >5°C above their summer maxima and are regularly exposed to temperatures above 30°C, which are lethal for corals elsewhere. The variability in resilience to ocean warming is critical to reef persistence, yet the scientific community lacks any standardized diagnostics to rapidly assess bleaching severity or resilience across different corals and locations. Using a newly developed portable experimental system that allows temperature manipulation in small volumes, we set out to i) determine empirical temperature thresholds for a range of Arabian Sea coral species, ii) examine the consistency of the exceptional thermal tolerance of these coral species across seasons and their latitudinal gradient, and iii) integrate these results into a thermal resilience map. Our approach fills a critical gap by determining coral thermal vulnerability thresholds in a high-resolution manner within days. The tested corals and reefs are then available for downstream applications, e.g. conservation, migration, restoration, assisted evolution.

Unfavourable nutrient levels before and during the 2012 Persian/Arabian Gulf bleaching event Wiedenmann, J.; D’Angelo, C.; Shuail, D.; Rajan, A; Grandcourt, E.; Burt, J.; Amos, C. Coral communities in the Southern Persian / Arabian Gulf have severely suffered from coral bleaching in 1996 and 1998. More recently, they have experienced a series of bleaching events in 2002, 2007, 2010, 2011, 2012 and 2017, putting their capacity to recover and survive under severe pressure. Recent research has found that a depletion of the water from nutrients, particularly from phosphate, renders corals more susceptible to bleaching. These conditions might be induced through nitrogen enrichment of coral reef waters and / or through a disturbance of the natural nutrient balance by phytoplankton blooms. We analysed data generated by remote sensing and in-situ measurements to pinpoint the environmental conditions accompanying the 2012 coral bleaching event in the Southern Arabian Gulf, comparing them to the non-bleaching years 2013-2015. During summer in 2012 and 2015, corals in Saadiyat reef were exposed to comparable levels of heat stress, yet they bleached only in 2012. The 2012 bleaching event coincided with high phytoplankton levels, low nitrate (N) and phosphate (P) concentrations and shifting N:P stoichiometry in the water column. In 2015, the nutrient levels were higher and comparable to those in the studied non-bleaching years. These data suggest that the coral bleaching event in 2012 was promoted by unfavourable nutrient levels in the water column.

Differential bacterial restructuring in coral species upon transplantation provides insight into microbiome flexibility Ziegler, M.; Grupstra, C.G.B.; Barreto, M.M.; Eaton, M.; BaOmar, J.; Zubier, K.; Al-Sofyani, A.; Turki, A.J.; Ormond, R.; Voolstra, C.R. The current global decline of coral reefs heightens the need to understand how corals respond to changing environmental conditions. Due to their long generation times, evolutionary change in corals is supposedly slow. However, corals are metaorganisms and restructuring of the associated bacterial community has been suggested as a faster means of contributing to holobiont adaptation. However, the potential for restructuring of bacterial communities across coral species, i.e. the flexibility to associate with different bacteria in different environments, has not been systematically investigated. Here we used 16S rRNA gene sequencing to study bacterial community dynamics in the corals Acropora hemprichii and Pocillopora verrucosa. Colony fragments of both corals were back- and cross-transplanted for 21 months between five sites with differing levels of anthropogenic impact, mostly from land-based sources of pollution in the Red Sea. We found that bacterial community structure responded in a host-specific manner. A. hemprichii harbored a highly flexible microbiome that differed between each level of anthropogenic impact to which the corals had been transplanted. In contrast, the P. verrucosa microbiome remained remarkably stable and was little affected by transplantation to different sites. Interestingly, upon cross-transplantation to unaffected sites, we found that microbiomes became indistinguishable from back-transplanted controls, suggesting the ability of microbiomes to recover. In light of our findings, we propose the term ‘microbiome flexibility’ to describe the potential for host-associated bacterial community restructuring upon environmental change. We suggest that distinct degrees of microbiome flexibility exist, potentially reflecting different holobiont adaptation mechanisms to respond to environmental change.