Coral Reefs
Corals
Corals are living organisms which add much colour and stunning views. Corals are actually vast colonies of identical polyps. Coral polyps are related to sea anemones and jellyfish. These measure just a few millimeters across but combine to form and act as though it were a single giant organism. Coral reefs contain diverse ecosystems, protects the coastlines and provides refuge to many other sea organisms.
Corals also form a breakwater for nearby coasts providing natural protection from storm surges. Corals have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities. Therefore they are very sensitive to changes in temperature. The corals receive their coloration from a micro-organism living within their tissues. Loss of particular micro-organism and / or a reduction in photosynthetic pigment concentrations result in coral bleaching. When higher water temperature persists for a few weeks the micro-organism that depends on some of their food leave their tissue, and corals become white and unhealthy which are called bleached.
Corals of Maldives
The Maldives consists entirely of coral reefs, the most diverse of all marine ecosystems. Coral reefs are known to host many levels of biodiversity ranging from microscopic planktonic organisms to sharks. The dominant species on reefs are corals and fish. Both these account for a large share of the diversity of coral reefs.
Although the corals are the major organisms that form the basic reef structure, there is bewildering array of other organisms associated with reefs, such that these areas are perhaps the most diverse and species rich areas that exist in the marine environment today. Members of practically all phyla and classes may be found on coral reefs.
Scleratinian corals of the Maldives have been relatively well studied. Descriptions of 147 species, and literature records of a further 94 species, making a total of 241 species have been recorded. The total number of coral species recorded from the Maldives to date is about 200, representing over 60 genera.
Coral Bleaching
Coral species live within a relatively narrow temperature margin, and anomalously low and high sea temperatures can induce coral bleaching. Bleaching events occur during sudden temperature drops accompanying intense upwelling episodes, (-3 degrees C to –5 degrees C for 5-10 days), seasonal cold-air outbreaks. Bleaching is much more frequently reported from elevated sea water temperature. A small positive anomaly of 1-2 degrees C for 5-10 weeks during the warm season will usually induce bleaching. The anomaly needed for bleaching has been consistently reduced due to the warming of the Arabian Sea around Maldives.
Coral reef bleaching can be induced by a variety of factors, alone or in combination. Disturbances affecting coral reefs include anthropogenic and natural events; among them climate change play a major role in the increase of coral bleaching. Higher sea temperatures from global warming have a grave impact on corals. Warmer water temperatures brought on by climate change stress corals by expelling the colourful algae that live within them, and alter coral reef communities by prompting coral bleaching. A one degree Celsius change in sea temperature would yield in losses of coral reefs. As climate change continues, bleaching too continues and health of the coral reefs deteriorate.
Coral bleaching events have increased in frequency and extent and subjected to unprecedented degradation worldwide during the past two decades. The frequency and scale of bleaching disturbances has increased dramatically since the late 70’s.
Recent History of Bleaching around the Maldives
The first known recorded mass bleaching event in Maldives was in 1998 killed over 90% of the shallow coral. Like many other parts of the world, Maldives was not prepared at the time for monitoring reefs in advance of the event. As a response, the Marine Research Centre established a National Coral Reef Monitoring Programme in 1998, representing sites that span the entire length of the Maldives. The monitoring continues to this day and some of its results have been published. The most recent mass-bleaching event of early 2016 was recorded relatively well in comparison to 1998.
Monitoring of Coral Bleaching
A citizen science program was initiated by Marine Research Centre (MRC) in June 2015, in collaboration with USAID supported Project REGENERATE implemented by IUCN, to prepare for the monitoring of predicted bleaching in the Maldives.
Updates on monitoring of coral bleaching:
References
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. https://portals.iucn.org/library/sites/library/files/documents/2017-025.pdf
Photographs: XL Catlin Seaview Survey, Coral bleaching in the Maldives – in pictures