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Costa Rica’s Largest Coral Reef Losing Diversity

coral reef
Cahuita’s Coral Reef  is Facing the Extinction of Its Weaker Coral Species.

Although the coral reef of Cahuita has kept on growing, thus giving the impression that everything is going well there under the sea, scientists recently disclosed the fact that although it is not actually shrinking, many of its species have now disappeared and it’s diversity is less abundant everyday. According to the Marine Sciences and Limnology Research Center (CIMAR), of the University of Costa Rica (UCR), only 27 of the 34 studied species exist today, that is to say that seven species have become extinct and will not be coming back. To put it in Scientist Carlos Jimenez’s words, quantity is not quality!

Jimenez has played a big part in the recent studies. In order to explain to the average person what is taking place, he compares the reef to a rainforest, something maybe we can understand a little better, and what is happening now is that we have a rainforest that has lost its big valuable trees, such as the Mahogany tree, and they have been replaced by smaller and less valuable small trees. These smaller trees are rapidly spreading, leaving little opportunity and space for the bigger ones to flourish again.

The study shows that only the stronger corals are now present in the reef of Cahuita, those that have so far been able to survive the many changes that have taken place in the sea throughout the last couple of decades, like the increase of sediments and chemicals, bad weather, etc. It doesn’t mean that the coral is necessarily not as attractive today, but it certainly has lost some of its unique beauty and value.

This loss in diversity happened for a variety of reasons, Jimenez said. The climatic changes are to blame, with more severe weather causing too much underwater disturbance that damages the coral. The amount of chemicals and garbage that is directly thrown and poured into the sea is obviously killing many marine species including the coral; agricultural chemical wastes go straight to the sea, no matter how far away they are dumped, they all eventually end up in the oceans.

Global warming and warmer seas are also to blame. The algae the coral needs to survive are dying off. The erosion caused by increased Costa Rica Land development adds to the problem as more and more trees are cut and more runoff finds its way to the ocean with nothing left to hold it in place. Finally, sand coming all the way from the Sahara desert in Africa also plays a small part. All these factors together prove to be a menacing enemy for the coral reef of Cahuita.

The research that led to these conclusions is being conducted by looking at the actual bones of the coral and the speed of their growth; the more sediments and chemicals that are found in the composition of the coral’s skeleton, the less chance the coral has to grow. The scientists are also comparing the conditions in which the coral lived some 30 years ago to the conditions of today. Old studies and the analysis of the coral skeleton offer a good perception of past ocean conditions and how today’s environment is affecting the coral in unique ways. It is similar to looking at the rings of a tree to look into the past, and to find out its age, health and any past diseases. The Star Coral in particular are able to give out interesting data; measuring up to two meters in height, this species has been around for hundreds of years and are the windows through which the past is exposed.

The coral reef of Cahuita is still one of the biggest in Costa Rica, and scientists are confident that some of its health and future diversity could be recovered, there is, however, a lot of work to be done there to enact this positive change.

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Written by Mireille

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