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

• Published in: Global Change Biology
• Main Authors: Genevier, Lily G C, Jamil, Tahira, Raitsos, Dionysios E, Krokos, George, Hoteit, Ibrahim
• Other Authors: Physical Sciences and Engineering (PSE) Division, Earth Science and Engineering Program, Remote Sensing Group, Plymouth Marine Laboratory, Prospect Place, The Hoe, PL1 3DH, United Kingdom.
• Format: Article in Journal/Newspaper
• Published: Wiley 2019
• Subjects: Marine heatwaves; Coral bleaching; Red Sea; Unexplored tropical regions; Conservation management tool; Bleaching threshold detection; Sea ice
• Online Access: http://hdl.handle.net/10754/631877; https://doi.org/10.1111/gcb.14652

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. We propose the use of Marine Heatwaves (MHWs) as a new approach for detecting coral reef zones susceptible to bleaching, using the Red Sea as a model system. Red Sea corals are exceptionally heat-resistant, yet bleaching events have increased in frequency. By applying a strict definition of MHWs on >30-year satellite-derived sea surface temperature observations (1985-2015), we provide an atlas of MHW hotspots over the Red Sea coral reef zones, which includes all MHWs that caused major coral 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. This article is protected by copyright. All rights reserved. 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.