Authors: Nizam Ibrahim, Maeesha Mohamed, Ahmed Basheer, Ismail Haleem, Fathimath Nistharan, Amir Schmidt, Rifath Naeem, Ameer Abdulla and Gabriel Grimsditch. This report should be cited as follows: Ibrahim, N., Mohamed, M., Basheer, A., Ismail, H., Nistharan, F., Schmidt, A., Naeem, R., Abdulla, A., and Grimsditch, G., 2017, Status of Coral Bleaching in the Maldives in 2016, Marine Research Centre, Malé, Maldives, 47 pages © Marine Research Centre, May 2017 Marine Research Centre H. White Waves, Moonlight Hingun, Malé-20025, Maldives Telephone: (+960) 332-2328, (+960) 332-2242 Facsimile: (+960) 332-2509 Email: [email protected] Website: www.mrc.gov.mv 1 EXECUTIVE SUMMARY This report represents the most comprehensive effort to monitor coral bleaching in the Maldives to date, using a combination of citizen science and expert scientist (governmental, academic and non-governmental) data sets. The 2015-2016 El Niño weather phenomena and associated sea surface temperature anomalies in 2016 caused one of the largest recorded episodes of mass bleaching in the Maldives. The El Niño began in 2015 and caused sea surface temperature anomalies in the Pacific Ocean, first affecting Hawaii in August 2015. The 2016 El Niño is considered to be one of the strongest El Niño events recorded since 1950. In Maldives, sea surface temperatures and degree heating weeks peaked from late April to mid May 2016, precipitating the bleaching event, with high temperatures over 32°C recorded. Although the bleaching event was devastating in its impact on many Maldivian coral reefs, the event provided the opportunity to enhance our understanding of bleaching patterns in a way that was not possible in 1998. A much larger and more detailed data set for the Maldives was collected in 2016 due to the continued monitoring of the National Coral Reef Monitoring Sites (NCRMS) by the Marine Research Centre (MRC), collaborations with international partners such as the International Union for the Conservation of Nature (IUCN) and an expansion of data collection to additional sites around the Maldives in 11 atolls, with the help of citizen scientists and resort marine biologists. A total of 71 sites, consisting of sheltered (sheltered from oceanic wave actions) and exposed (exposed to oceanic wave actions) sites, across 11 atolls within 0 m to 13 m depth range were surveyed from March to June 2016 to understand the severity of the bleaching event. The overall percentage of bleached corals recorded across all 71 sites in the Maldives is 73%, indicating a severe bleaching event. Analyses of the multiple monitoring efforts suggest that 66% of corals bleached at a depth of 0m to 7 m, and 77% of corals bleached in depth from 7m to 13 m. Furthermore, 72% corals in sheltered sites and 74% of corals in exposed sites bleached, with no significant difference in bleaching response detected between exposures. The bleaching susceptibility index for coral genera shows free-living genera such as Fungia, Herpolitha, Cycloseris and Halomitra to be highly susceptible to bleaching. Other genera EXECUTIVE SUMMARY EXECUTIVE 2 found to be highly susceptible are Pectinia, Merulina, Gardinoseris and Acropora, which is the most dominant reef building coral genus in Maldives. On the other end of the spectrum corals from the more resistant Faviidae family, for example Favites and Leptastrea, and Poritidae family, for example Porites and Goniopora, were observed to be more resistant and less susceptible to bleaching. Assessments of post-bleaching coral mortality show a high decline in live coral cover in the sites surveyed. The highest levels of mortality occurred amongst corals of the Acropora genus, with low levels of mortality within the Porites genus. Despite the high impact of the event, a number of sites (e.g. Drift Thelu Veliga House Reef in South Ari Atoll, Blue Cove and Coral Gardens at Magoodhoo island in Faafu Atoll, Reethi Beach West in Baa Atoll, Sonevafushi House Reef in Baa Atoll, and Emboodhoo Finolhu Inner Reef in South Malé Atoll) were reported to have less than 45% incidence of coral bleaching and more than 25% live coral cover. These sites have been defined as ‘hope spots’, and warrant further attention through follow up surveys and possible investment in management and protection. EXECUTIVE SUMMARY EXECUTIVE 3 CONTENTS EXECUTIVE SUMMARY ............................................................................................................................................ 2 CONTENTS .............................................................................................................................................................. 4 FOREWORD ............................................................................................................................................................. 5 ABBREVIATIONS AND ACRONYMS .......................................................................................................................... 6 INTRODUCTION ...................................................................................................................................................... 7 BACKGROUND ........................................................................................................................................................ 7 Pre-bleaching preparations .............................................................................................................................. 10 Aerial photos from seaplane pilots .................................................................................................................. 13 NOAA Coral Reef Watch, predictions ............................................................................................................... 14 Formation of inter-agency taskforce on coral bleaching ................................................................................. 17 METHODS ............................................................................................................................................................. 18 Crown-of-Thorns starfish (COTS) reporting ...................................................................................................... 20 Sites surveyed .................................................................................................................................................. 21 RESULTS ................................................................................................................................................................ 23 Bleaching severity ............................................................................................................................................ 25 Bleaching severity by depth ............................................................................................................................. 25 Bleaching severity by exposure ........................................................................................................................ 25 Bleaching over time in <7 m depth .................................................................................................................. 26 Bleaching over time in 7-13 m depth ............................................................................................................... 26 Bleaching index for coral genera ...................................................................................................................... 27 Hope Spots ....................................................................................................................................................... 29 Mortality and survival of Acropora in Kaafu Atoll ............................................................................................ 31 Mortality and survival of Porites in Kaafu Atoll ................................................................................................ 31 Coral bleaching relative to live coral cover in all the atolls surveyed .............................................................. 32 Other stressors to Maldivian coral reefs .............................................................................................................. 32 Crown-of-Thorns starfish (COTS) outbreaks .................................................................................................... 33 DISCUSSION .......................................................................................................................................................... 33 Hope spots ....................................................................................................................................................... 35 RECOMMENDATIONS ........................................................................................................................................... 39 Developing a national coral bleaching response plan (CBRP) .......................................................................... 39 Strengthening National Coral Reef Monitoring Programme (NCRMP) at MRC ............................................... 39 Identify and resurvey ‘hope spots’ to measure mortality of corals and consider special protection or management .................................................................................................................................................... 40 Develop a plan for aerial bleaching surveys ..................................................................................................... 41 LESSONS LEARNED ...............................................................................................................................................