Family Composition

Over a thousand species of corals call the waters of Maldives their home. The ones most at risk from the dangers of ocean acidification are hard corals because they use calcium carbonate to make their skeletons and create the structure of coral reefs.With rising ocean acidity these structures are dissolving and becoming more brittle therefore falling apart. Two varieties of these corals are massive and branching. Massive corals are characterized by their their slow and relatively flat growth while branching corals grow quickly and in a tree like manner (Goreau, 1979). A few of the common families of  these hard corals  inhabiting the warm waters of Maldives include:

Pocilloporidae (branching)

http://anniekatec.blogspot.com/2010/08/soaring-temps-cause-mass-coral-killing.html

Acroporidae (branching)

http://anniekatec.blogspot.com/2010/08/soaring-temps-cause-mass-coral-killing.html

Faviidae (massive)

http://www.flickr.com/photos/mal-b/6981494031/

Poritidae(massive)

http://images.whatsthatfish.com/480x360/lleyu1nQ8l.jpg

Agariciidae(massive)

http://images.whatsthatfish.com/480x360/nLf3tKDt8i.jpg

Merulinidae(Massive)

http://fishoncomputer.files.wordpress.com/2012/02/img_81561.jpg?w=640&h=426

Siderastreidae (massive)

http://images.whatsthatfish.com/480x360/tfcrrz66NZ.jpg

Image/Text/Data from the University of Illinois WW2010 Project

    In 1998 Maldives coral reefs were devastated by a major El Niño event that damaged most of the surrounding reefs. An El Niño event is cause by a weakening in Easterly trade winds (Easterly winds come from the east and move west). This allows warmer waters from the Western Pacific to disperse causing an increased SST all along the equator ("El Nino..", 2010). Researchers were able to study the effects and gain a lot of insight on not only how corals respond to bleaching events, but also how different species react.  Scientists constructed artificial structures in 1990 to monitor species ratios. It was found that the El Niño warming event caused 98% of the branching corals to die while the majority of massive corals managed to survive (Edwards, 2001). This death rate caused by the warming event creates two very different community structures when comparing the pre and post bleaching populations. Pre-bleaching coral community consisted of 95% branching and 5% massives at a total population of 1589 individuals and then after 1998 switched to 3% branching corals and 97% massives with a much smaller population count of 248. These results were also seen by another study conducted by Dr. McClanahan. His team found that the community structure switched from large number of branching to massive corals.  He predicted that if climates continue to rise, there will be a permanent change in family composition of coral reefs (T.R McClanahan, 2000). 

This figure shows how the community is composed of more massive corals
rather than branching but begins to revert back as times passes (Edward 2001)

                From these results, it is apparent that branching corals are very poor at handling the increase in temperature. Massive corals are able to cope with this change much more effectively which is most likely due to thick protective tissue compared to the tubular formed branching corals with their thinner tissues.  However, the graph demonstrates that community structure appears to be shifting back to the original proportions.  This is likely due to the slow growth rates of the massives compared to the branching species which are able to propagate much more quickly in the ideal cooler conditions.