Coral Reefs

, Volume 39, Issue 1, pp 1–11 | Cite as

Participatory reporting of the 2016 bleaching event in the Western Indian Ocean

  • Mishal GudkaEmail author
  • David Obura
  • James Mbugua
  • Said Ahamada
  • Ulli Kloiber
  • Tammy Holter


Climate change, coupled with an El Niño, caused a devastating bleaching event in the Western Indian Ocean (WIO) in 1998. Similar extreme conditions at the end of 2015 meant that there was a very high risk of widespread bleaching in the WIO at the start of 2016. In anticipation of a regional bleaching event, a citizen-science online reporting tool was developed to collect data in broad categories of bleaching and mortality from various stakeholders across the region, e.g. general public, scientists, reef managers, divers. The main objectives were to (i) document in real-time the impacts of the 2016 coral bleaching event at a regional scale and (ii) demonstrate the value of basic data to illustrate and understand important trends. A total of 698 records from 55 organisations and over 80 observers were collected through the online reporting form and via email. Thermal stress across the WIO during the bleaching season (January–May) was high enough to cause widespread bleaching and significant mortality, with reef sites on average, experiencing a maximum of 5.4 Degree-Heating-Weeks (DHW), with some sites experiencing up to 15 DHW. During the peak-bleaching months, 37% of sites were affected by high or extreme bleaching, while 8.5% of sites showed no evidence of bleaching. Seychelles was the most affected by bleaching with 90% of reported sites showing high or extreme bleaching, followed by Tanzania, Comoros, Reunion and Mauritius. Sites in the Mozambique Channel (south and north) were the least affected by bleaching. Over 60% of sites experienced some level of bleaching-induced coral mortality from April onwards, but the impact was heterogeneous, with reefs in some areas showing substantial recovery from bleaching and others showing almost no recovery. As the first effort in the WIO to gather bleaching data at this scale during a major bleaching event, this study has shown that participatory data collection from various stakeholders, even at a basic level, can reveal important regional-scale, real-time trends and information about coral bleaching.


Coral bleaching third global bleaching event Western Indian Ocean Coral reefs Climate change El Niño 



The authors would like to acknowledge the funding and support provided for the regional data collection initiative by the European Union through the Biodiversity Project of the Indian Ocean Commission. We would also like to recognize the Western Indian Ocean Global Coral Reef Monitoring Network participants and thank everyone who responded to the call and contributed their data and records. The full list of all the institutions and individuals who contributed to the initiative is provided as a table in the Electronic Supplementary Material.

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Supplementary material

338_2019_1851_MOESM1_ESM.docx (478 kb)
Supplementary file1 (DOCX 479 kb)


  1. Bacha Gian S, Munbodhe V, Soogun N, Raffin J (2017) Mauritius national chapter, GCRMN (2017). Coral Reef Status Report for the Western Indian Ocean. (2017). IOC/GCRMN, pp 78–87 [doi: 10.13140/RG.2.2.20642.07366]Google Scholar
  2. Celliers L, Schleyer M (2002) Coral bleaching on high-latitude marginal reefs at Sodwana Bay, South Africa. Mar Pollut Bull 44:1380–1387CrossRefGoogle Scholar
  3. Collins C, Hermes JC, Reason CJC (2014) Mesoscale activity in the Comoros Basin from satellite altimetry and a high-resolution ocean circulation model. J Geophys Res Oceans 119:4745–4760CrossRefGoogle Scholar
  4. Dinno A (2015) Nonparametric pairwise multiple comparisons in independent groups using Dunn’s test. Stata J 15:292–300CrossRefGoogle Scholar
  5. Donner SD, Rickbeil GJM, Heron SF (2017) A new, high-resolution global mass coral bleaching database. PLoS ONE 12:e0175490CrossRefGoogle Scholar
  6. Eakin CM, Liu G, Gomez AM, De la Couri JL, Heron H, Skirving W, Geiger EF, Marsh BL, Tirak KV, Strong AE (2018) Unprecedented three years of global coral bleaching 2014–17. State of the Climate in 2017. Bulletin of the American Meteorological Society, pp S74–S75Google Scholar
  7. Eakin CM, Morgan JA, Heron SF, Smith TB, Liu G, Alvarez-Filip L, Baca B, Bartels E, Bastidas C, Bouchon C, Brandt M, Bruckner AW, Bunkley-Williams L, Cameron A, Causey BD, Chiappone M, Christensen TRL, Crabbe MJC, Day O, de la Guardia E, Díaz-Pulido G, DiResta D, Gil-Agudelo DL, Gilliam DS, Ginsburg RN, Gore S, Guzmán HM, Hendee JC, Hernández-Delgado EA, Husain E, Jeffrey CFG, Jones RJ, Jordán-Dahlgren E, Kaufman LS, Kline DI, Kramer PA, Lang JC, Lirman D, Mallela J, Manfrino C, Maréchal J-P, Marks K, Mihaly J, Miller WJ, Mueller EM, Muller EM, Toro CAO, Oxenford HA, Ponce-Taylor D, Quinn N, Ritchie KB, Rodríguez S, Ramírez AR, Romano S, Samhouri JF, Sánchez JA, Schmahl GP, Shank BV, Skirving WJ, Steiner SCC, Villamizar E, Walsh SM, Walter C, Weil E, Williams EH, Roberson KW, Yusuf Y (2010) Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005. PLoS ONE 5:e13969CrossRefGoogle Scholar
  8. Faure G, Guillaume M, Payri C, Thomassin B, Michel V-P, Vasseur P (1984) Massive bleaching and death of corals in the Mayotte reef ecosystem (SW Indian Ocean). Comptes Rendus Académie Sci 299 sér. III:637–642Google Scholar
  9. Floros CD, Samways MJ, Armstrong B (2004) Taxonomic patterns of bleaching within a South African coral assemblage. Biodivers Conserv 13:1175–1194CrossRefGoogle Scholar
  10. Forrester G, Baily P, Conetta D, Forrester L, Kintzing E, Jarecki L (2015) Comparing monitoring data collected by volunteers and professionals shows that citizen scientists can detect long-term change on coral reefs. J Nat Conserv 24:1–9CrossRefGoogle Scholar
  11. Gamoyo MJ (2018) Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean. Ph.D. thesis, University of Cape Town, p 151Google Scholar
  12. Goreau T, McClanahan T, Hayes R, Strong A (2000) Conservation of Coral Reefs after the 1998 Global Bleaching Event. Conserv Biol 14:5–15CrossRefGoogle Scholar
  13. Grimsditch G, Mwaura JM, Kilonzo J, Amiyo N (2010) The Effects of Habitat on Coral Bleaching Responses in Kenya. Ambio 39:295–304CrossRefGoogle Scholar
  14. Gudka M, Obura DO (2017) The 2016 coral bleaching event in the Western Indian Ocean - overview, GCRMN (2017). Coral Reef Status Report for the Western Indian Ocean. (2017). IOC/GCRMN, pp 26–37. doi: 10.13140/RG.2.2.20642.07366Google Scholar
  15. Gudka M, Obura DO, Mwaura J, Porter S, Yahya S, Mabwa R (2018) Impact of the 3rd Global Coral Bleaching Event on the Western Indian Ocean in 2016. GCRMN/IOC. CrossRefGoogle Scholar
  16. Hill NO, Davidson J, Silva I, Mucave S, Muaves L, Guissamulo A, Debney A, Garnier J (2009) Coral and Reef Fish in the Northern Quirimbas Archipelago, Mozambique: A First Assessment. West Indian Ocean J Mar Sci 8:113–125Google Scholar
  17. Hughes TP, Anderson KD, Connolly SR, Heron SF, Kerry JT, Lough JM, Baird AH, Baum JK, Berumen ML, Bridge TC, Claar DC, Eakin CM, Gilmour JP, Graham NAJ, Harrison H, Hobbs J-PA, Hoey AS, Hoogenboom M, Lowe RJ, McCulloch MT, Pandolfi JM, Pratchett M, Schoepf V, Torda G, Wilson SK (2018) Spatial and temporal patterns of mass bleaching of corals in the Anthropocene. Science 359:80–83CrossRefGoogle Scholar
  18. Hughes TP, Kerry JT, Álvarez-Noriega M, Álvarez-Romero JG, Anderson KD, Baird AH, Babcock RC, Beger M, Bellwood DR, Berkelmans R, Bridge TC, Butler IR, Byrne M, Cantin NE, Comeau S, Connolly SR, Cumming GS, Dalton SJ, Diaz-Pulido G, Eakin CM, Figueira WF, Gilmour JP, Harrison HB, Heron SF, Hoey AS, Hobbs J-PA, Hoogenboom MO, Kennedy EV, Kuo C, Lough JM, Lowe RJ, Liu G, McCulloch MT, Malcolm HA, McWilliam MJ, Pandolfi JM, Pears RJ, Pratchett MS, Schoepf V, Simpson T, Skirving WJ, Sommer B, Torda G, Wachenfeld DR, Willis BL, Wilson SK (2017) Global warming and recurrent mass bleaching of corals. Nature 543:373–377CrossRefGoogle Scholar
  19. Kayanne H (2017) Validation of degree heating weeks as a coral bleaching index in the northwestern Pacific. Coral Reefs 36:63–70CrossRefGoogle Scholar
  20. Marshall NJ, Kleine DA, Dean AJ (2012) CoralWatch: education, monitoring, and sustainability through citizen science. Front Ecol Environ 10:332–334CrossRefGoogle Scholar
  21. Marshall PA, Schuttenberg H (2006) A reef manager’s guide to coral bleaching. Great Barrier Reef Marine Park Authority, AustraliaGoogle Scholar
  22. McClanahan T, Muthiga N, Mangi S (2001) Coral and algal changes after the 1998 coral bleaching: interaction with reef management and herbivores on Kenyan reefs. Coral Reefs 19:380–391CrossRefGoogle Scholar
  23. McClanahan TR, Ateweberhan M, Darling ES, Graham NAJ, Muthiga NA (2014) Biogeography and Change among Regional Coral Communities across the Western Indian Ocean. PLoS ONE 9:e93385CrossRefGoogle Scholar
  24. McClanahan TR, Ateweberhan M, Graham NAJ, Wilson SK, Sebastián CR, Guillaume MMM, Bruggemann JH (2007) Western Indian Ocean coral communities: bleaching responses and susceptibility to extinction. Mar Ecol Prog Ser 337:1–13CrossRefGoogle Scholar
  25. McClanahan TR, Baird AH, Marshall PA, Toscano MA (2004) Comparing bleaching and mortality responses of hard corals between southern Kenya and the Great Barrier Reef, Australia. Mar Pollut Bull 48:327–335CrossRefGoogle Scholar
  26. McDonald JH (2014) Handbook of Biological Statistics. Sparky House PublishingGoogle Scholar
  27. NOAA (2015) NOAA declares third ever global coral bleaching event | National Oceanic and Atmospheric Administration.
  28. NOAA (2017) Global coral bleaching event likely ending | National Oceanic and Atmospheric Administration.
  29. NOAA Coral Reef Watch (2016) NOAA Coral Reef Watch Version 3.1 monthly Global 5-km Satellite Coral Bleaching Degree Heating Week Product, Jan, 2016-May. 2016. []
  30. Normile D (2016) El Niño’s warmth devastating reefs worldwide. Science 352:15–16CrossRefGoogle Scholar
  31. Obura DO (2001) Can differential bleaching and mortality among coral species offer useful indicators for assessment and management of reefs under stress? Bull Mar Sci 69:421–442Google Scholar
  32. Obura DO (2012) The Diversity and Biogeography of Western Indian Ocean Reef-Building Corals. PLoS ONE 7:e45013CrossRefGoogle Scholar
  33. Obura DO (2014) Coral Reef Monitoring Manual - South-West Indian Ocean Islands. Indian Ocean Commission [],
  34. Obura DO (2016) Coral Bleaching monitoring guide – Western Indian Ocean. Indian Ocean Commission []
  35. Obura DO, Bigot L, Benzoni F (2018) Coral responses to a repeat bleaching event in Mayotte in 2010. PeerJ 6:e5305CrossRefGoogle Scholar
  36. Obura DO, Causey B, Church J (2006) Management Response to a Bleaching Event. Coral Reefs and Climate Change: Science and Management. American Geophysical Union (AGU), pp 181–206Google Scholar
  37. Obura DO, Gudka M, Abdou Rabi F, Bijoux J, Freed S, Gian SB, J Maharavo, J Mwaura, S Porter, E Sola, J Wickel, S Yahya, S Ahamada (2017) Coral reef status report for the Western Indian Ocean (2017). Global Coral Reef Monitoring Network (GCRMN)/Indian Ocean Commission (IOC), 144. doi: 10.13140/RG.2.2.20642.07366Google Scholar
  38. Pratchett MS, McCowan D, Maynard JA, Heron SF (2013) Changes in Bleaching Susceptibility among Corals Subject to Ocean Warming and Recurrent Bleaching in Moorea. French Polynesia PLoS ONE 8:e70443CrossRefGoogle Scholar
  39. Schott F, Xie S-P, McCreary JP (2009) Indian Ocean circulation and climate variability. Rev Geophys 47:1–46CrossRefGoogle Scholar
  40. Schouten MW, de Ruijter WPM, van Leeuwen PJ, Ridderinkhof H (2003) Eddies and variability in the Mozambique Channel. Deep Sea Res Part II Top Stud Oceanogr 50:1987–2003CrossRefGoogle Scholar
  41. Spencer T, Teleki KA, Bradshaw C, Spalding M (2000) Coral Bleaching in the Southern Seychelles During the 1997–1998 Indian Ocean Warm Event. Mar Pollut Bull 40:569–586CrossRefGoogle Scholar
  42. UCLA: Statistical Consulting Group (2011) Choosing the Correct Statistical Test in SAS, Stata, SPSS and R.
  43. Wilkinson C (2001) Status of Coral Reefs of the World: 2000. Australian Institute of Marine Science/Global Coral Reef Monitoring Network.
  44. Wilkinson C, Linden O, Cesar H, Hodgson G, Rubens J, Strong A (1999) Ecological and socioeconomic impacts of 1998 coral mortality in the Indian Ocean: An ENSO impact and a warning of future change? Ambio 28:188–196Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Mishal Gudka
    • 1
    Email author
  • David Obura
    • 1
  • James Mbugua
    • 1
  • Said Ahamada
    • 2
  • Ulli Kloiber
    • 3
  • Tammy Holter
    • 4
  1. 1.Coastal Oceans Research and Development Indian Ocean (CORDIO) East AfricaMombasaKenya
  2. 2.Indian Ocean CommissionEbèneMauritius
  3. 3.Chumbe Island Coral Park LtdZanzibarTanzania
  4. 4.Scuba Do ZanzibarKendwa, ZanzibarTanzania

Personalised recommendations