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