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

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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.

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  • 20 September 2019

    This erratum has been initiated as authors first and last names appeared inverse in the original article and should be correctly read as.


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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.

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Correspondence to Mishal Gudka.

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Gudka, M., Obura, D., Mbugua, J. et al. Participatory reporting of the 2016 bleaching event in the Western Indian Ocean. Coral Reefs 39, 1–11 (2020).

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