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 5 yr (2013–2017) 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 2 months (mean 55.1 ± 3.9 d above bleaching temperatures and nearly 2 weeks above lethal temperatures (11.8 ± 2.4 d), substantially longer than in the non-bleaching years (2013–2016) 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 1 yr. This mass mortality did not cause dramatic shifts in community composition as earlier bleaching events had removed most sensitive taxa. An exception was 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 are not optimistic.

Causes and consequences of the 2017 coral bleaching event in the southern Persian/Arabian Gulf

Coral reefs are subject to coral bleaching manifested by the loss of endosymbiotic algae from coral host tissue. Besides algae, corals associate with bacteria. In particular, bacteria residing in the surface mucus layer are thought to mediate coral health, but their role in coral bleaching is unknown. We collected mucus from bleached and healthy Porites lobata colonies in the Persian/Arabian Gulf (PAG) and the Red Sea (RS) to investigate bacterial microbiome composition using 16S rRNA gene amplicon sequencing. We found that bacterial community structure was notably similar in bleached and healthy corals, and the most abundant bacterial taxa were identical. However, fine-scale differences in bacterial community composition between the PAG and RS were present and aligned with predicted differences in sulfur- and nitrogen-cycling processes. Based on our data, we argue that bleached corals benefit from the stable composition of mucus bacteria that resemble their healthy coral counterparts and presumably provide a conserved suite of protective functions, but monitoring of post-bleaching survival is needed to further confirm this assumption. Conversely, fine-scale site-specific differences highlight flexibility of the bacterial microbiome that may underlie adjustment to local environmental conditions and contribute to the widespread success of Porites lobata.

/pdf/stable-mucus-associated-bacterial-communities-in-bleached-58rryyd0un.pdf

Stable mucus-associated bacterial communities in bleached and healthy corals of Porites lobata from the Arabian Seas.

This publication is supported by the Office of Sponsored Research (OSP) at King Abdullah University of Science and Technology (KAUST) under the Virtual Red Sea Initiative (REP/1/3268-01-01). We are grateful to the Met Office, the Group for High Resolution SST (GHRSST), the Global Telecommunications System (GTS), and EUMETSAT Ocean and Sea Ice Satellite Applications Facility (OSI-SAF) for making the OSTIA database available, and to UNEP-WCMC for providing the Global distribution of warm-water coral reefs database. We thank Ute Langner for processing the coral reef locations, and John A. Gittings for his initial constructive comments.

/pdf/marine-heatwaves-reveal-coral-reef-zones-susceptible-to-4o6ennagmg.pdf

Marine heatwaves reveal coral reef zones susceptible to bleaching in the Red Sea

https://ecommons.luc.edu/cgi/viewcontent.cgi?article=1214&context=business_facpubs

Coral reefs of the Red Sea — Challenges and potential solutions

Response of bleached and symbiotic sea anemones to plastic microfiber exposure.

Coral bleaching continues to be one of the most devastating and immediate impacts of climate change on coral reef ecosystems worldwide. In 2015, a major bleaching event was declared as the "3rd global coral bleaching event" by the United States National Oceanic and Atmospheric Administration, impacting a large number of reefs in every major ocean. The Red Sea was no exception, and we present herein in situ observations of the status of coral reefs in the central Saudi Arabian Red Sea from September 2015, following extended periods of high temperatures reaching upwards of 32.5°C in our study area. We examined eleven reefs using line-intercept transects at three different depths, including all reefs that were surveyed during a previous bleaching event in 2010. Bleaching was most prevalent on inshore reefs (55.6% ± 14.6% of live coral cover exhibited bleaching) and on shallower transects (41% ± 10.2% of live corals surveyed at 5m depth) within reefs. Similar taxonomic groups (e.g., Agariciidae) were affected in 2015 and in 2010. Most interestingly, Acropora and Porites had similar bleaching rates (~30% each) and similar relative coral cover (~7% each) across all reefs in 2015. Coral genera with the highest levels of bleaching (>60%) were also among the rarest (<1% of coral cover) in 2015. While this bodes well for the relative retention of coral cover, it may ultimately lead to decreased species richness, often considered an important component of a healthy coral reef. The resultant long-term changes in these coral reef communities remain to be seen.

/pdf/in-situ-observations-of-coral-bleaching-in-the-central-saudi-2dxw8tqwcl.pdf

In situ observations of coral bleaching in the central Saudi Arabian Red Sea during the 2015/2016 global coral bleaching event

This research was supported by the KAUST Office of Competitive Research Funds (OCRF) under Award No. CRG-1-2012-BER-002 and baseline research funds to M.L.B. We thank Dr. Vanessa Robitzch Sierra (Universidad Austral de Chile) for her generous help with the genetic analysis of the specimens. We also thank the staff at the Bioscience CORE laboratory at King Abdullah University of Science and Technology for their sequencing sup-port. Lastly, we are grateful to Dream Divers and many members of the Reef Ecology Lab at King Abdullah University of Science and Technology, past and present, for their logistical support. All specimens from the Red Sea and Djibouti were obtained in ac-cordance with local regulations. For fieldwork in the Maldives conducted during the first Maldives Reef Biodiversity Workshop, we thank the University of Milano-Bicocca Marine Research and High Education Centre in Magoodhoo, the Ministry of Fisheries and Agriculture, Republic of Maldives and the community of Maghoodhoo, Faafu Atoll. Samples from the Maldives were col-lected under research permit OTHR30-D/INDIV/2014/185. Sampling at Papua New Guinea was undertaken under a research visa issued by the government of Papua New Guinea. Verbal per-missions were granted by Mrs. Cecilie Benjamin (Chair of the Board, Mahonia Na Dari Research and Conservation Centre, Kilu) and Mr. Thomas Koi (Village Elder and representative of the Local Marine Management). Samples collected from the Great Barrier Reef were permitted by the Great Barrier Reef Marine Park Authority (permits G13/35980.1, P02/0025-4.0 and LHIMP/R/2014/001). Samples from Christmas Island were collected under exemption number 2087. Samples from Moorea (French Polynesia) were col-lected under permit N 1111/MCE/ENV issued by the Ministere de la Culture et de l Environnement.

/pdf/comparative-phylogeography-of-three-host-sea-anemones-in-the-2ncfz3cpj6.pdf

Comparative phylogeography of three host sea anemones in the Indo‐Pacific

Scleractinian corals are colonial animals with a range of life history strategies, making up diverse species assemblages that define coral reefs. We tagged and tracked approximately 30 colonies from each of 11 species during seven trips spanning six years (2009-2015) in order to measure their vital rates and competitive interactions on the reef crest at Trimodal Reef, Lizard Island, Australia. Pairs of species were chosen from five growth forms where one species of the pair was locally rare (R) and the other common (C). The sampled growth forms were massive [Goniastrea pectinata (R) and G. retiformis (C)], digitate [Acropora humilis (R) and A. cf. digitifera (C)], corymbose [A. millepora (R) and A. nasuta (C)], tabular [A. cytherea (R) and A. hyacinthus (C)] and arborescent [A. robusta (R) and A. intermedia (C)]. An extra corymbose species with intermediate abundance, A. spathulata was included when it became apparent that A. millepora was too rare on the reef crest, making the 11 species in total. The tagged colonies were visited each year in the weeks prior to spawning. During visits, two or more observers each took 2-3 photographs of each tagged colony from directly above and on the horizontal plane with a scale plate to track planar area. Dead or missing colonies were recorded and new colonies tagged in order to maintain approximately 30 colonies per species throughout the six years of the study. In addition to tracking tagged corals, 30 fragments were collected from neighboring untagged colonies of each species for counting numbers of eggs per polyp (fecundity); and fragments of untagged colonies were brought into the laboratory where spawned eggs were collected for biomass and energy measurements. We also conducted surveys at the study site to generate size structure data for each species in several of the years. Each tagged colony photograph was digitized by at least two people. Therefore, we could examine sources of error in planar area for both photographers and outliners. Competitive interactions were recorded for a subset of species by measuring the margins of tagged colony outlines interacting with neighboring corals. The study was abruptly ended by Tropical Cyclone Nathan (Category 4) that killed all but nine of the over 300 tagged colonies in early 2015. Nonetheless, these data will be of use to other researchers interested in coral demography and coexistence, functional ecology, and parametrizing population, community and ecosystem models. The data set is not copyright restricted, and users should cite this paper when using the data.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ecy.4017

Madeleine Anne Emms

Papers

In situ observations of coral bleaching in the central Saudi Arabian Red Sea during the 2015/2016 global coral bleaching event

Comparative phylogeography of three host sea anemones in the Indo‐Pacific

Six years of demography data for 11 reef coral species.