Surveying mass bleaching in the Maldives with IUCN

Image: bleached coral in the Maldives


In early April, the first sighting of bleaching from the third global coral bleaching event began to be documented in the Maldives. From the reports, the southernmost atoll, Addu was the first affected. It was not long before bleaching reports came in from all over the country to the International Union for the Conservation of Nature (IUCN) and the Maldives Marine Research Centre (MRC).  Pilots from the sea plane company Trans Maldivian Airlines (TMA) were sending pictures of white reef flats to MRC by the middle of April.  By this stage, it was evident the Maldives was facing a mass bleaching event and potential mortality similar to the 1998 event.



A greater understanding


The 1998 event was one of the first alarms that carbon emissions are changing the planet in ways that affect important ecosystems such as coral reefs.  However, as a global community, we collectively pressed the snooze button. Unlike the 1998 mass bleaching event, the global and Maldivian coral reef science community is well poised to measure the full effects of this event. In 1998 there was a significant effort by coral reefs scientists such as Husain Zahir at the MRC to measure recovery of coral cover from the mass mortality event. However, there were no data on coral cover and benthic community composition because no one saw it coming. Thanks to the efforts carried out by coral reef and climate scientists in the years since 1998, we now understand the thermal thresholds for corals before they start to bleach, making it possible to predict when bleaching would start happening in different areas of the world. 



Important expeditions


In April and May 2015 the Global Change Institute (GCI)/XL Catlin Seaview Survey and the IUCN carried out expeditions to collect valuable baseline information on the coral reefs before this current bleaching event. The first leg was the XL Catlin Seaview Survey team, which covered large areas of forereefs throughout the Central Maldives region. The second leg, which followed shortly afterwards was the IUCN expedition under Project Regenerate*, which focused on looking at differences in coral communities and fish biomass amongst local community, resort, and uninhabited islands in the North Ari Atoll. Team members from the two expedition legs are now working closely together alongside the MRC, with hope the data from these expeditions will go far in understanding and protecting Maldivian Coral Reefs.


The partnership with IUCN has allowed for the opportunity for me to be invited by the project director Dr. Ameer Abdulla to join his team of coral reef scientists to survey the bleaching sites in North Ari Atoll. The team, made up of coral, fish, and social scientists, aimed to not only understand the ecological impact of mass bleaching on coral reefs, but also the social perceptions and consequences on bleaching toward local islanders and resorts. This data is critical to describe the socio-ecological system that underpins interactions between Maldivian people and the coral reefs. 


I carried out video transects along 3 X 50m transects at 10 and 5 meters depth. These videos will then be analysed to score the number of corals bleaching along with their taxonomic genera, morphology, and size. This information will be useful to understand impacts of thermal stress, with regard to bleaching severity and vulnerability of different types of coral. Although most of the sites are heavily bleached, there is more bleaching among the Acroporidae family, which are known to be far less tolerant of thermal stress than families such as Poritidae or Faviidae.  Hussein Zahir, who is on the expedition, explained to us that most of the reefs were covered in a type of macroalgae known as Dictyota sp in 1998 after the bleaching event, and it took around 3-5 years to see signs of coral recovery and most sites. 



Confidence for the future


In the absence of future thermal events, there is confidence that reefs in the Maldives will recover from this event, due to the ban on exportation on important herbivores fish species, which are essential for coral reef recovery from mass mortality events. However the full extent of mortality and potential recovery is unknown, and it is important to establish consistent and sound monitoring of recovery through time to understand the full implications of this event.  The XL Catlin Seaview Survey, IUCN and MRC have collected much needed baseline data on the condition of the reef prior to bleaching. The teams at IUCN, MRC and GCI are now eager to resurvey these sites 6-12 months after the bleaching event in order measure to mortality form the event. This information allows scientists to further understand the affect of severe temperature anomalies from climate change are having on coral reef ecosystems around the world.


*Project regenerate funded by the United States Agency for International Development (USAID)