Nutrition Colombia , Colombia, Wednesday, May 06 of 2015, 09:05

Colombian Caribbean corals are dying of asphyxiation

A UNal research project determined that a disease known as black band disease (BBD) caused by a consortium covers corals and kills live tissue

UN/DICYT Cyanotoxins and a bacterial physical effect grow on corals producing an anoxia effect (lack of tissue oxygen) which leads to their death. 


One of the causes of the disappearance of these ecosystems is infectious diseases, which could be associated to climate change and water temperature increase. 


Department of Biology and Genetics Institute Luis Fernando Cadavid, says that the research project analyzed which were the pathological alterations in coral cells which could explain their death to a condition known as black band disease. 


“Coral reefs are the most diverse ecosystems in the planet but during the last 30 years 50 per cent of the live coral reef coverage in the Caribbean has disappeared,” he said. 


Black band disease is caused by a bacterial consortium predominately of cyanobacteria (bacteria which produce toxins that induce cell death) which covers corals and kills live tissue leaving the skeleton exposed. 


With sequencing cutting-edge technology, they carried out the sequence of the whole transcriptome (set of all RNA molecules) and determined that through these cyanotoxins and the bacterial effect, coral cells lose oxygen supply. 


These results were part of research project which purpose was to identify coral immune response mechanisms against potential pathogens or agents which could produce disease. 


Researchers carried out a bacterial challenge on samples taken from the Santa Marta Bay on the Colombian Caribbean and placed them on coral colonies to induce an immune response. 


Coral transcriptome sequencing allowed identifying which genes expressed as a consequence of this bacterial contact belonged to the immune system.  They observed a high diversity of coral defense genes which were classified into three groups. 


The first group was recognition genes which are in charge of directly contacting the pathogens; the second group which are genes involved in intracellular signaling and allow molecular system comprehensive functioning; and the third group are effector molecules which are in charge of neutralizing and destroying pathogens. 


“We discovered great diversity, most of all of molecules which are part of the immunological recognition group,” said the expert. 


This pioneering coral immunity work performed by UNal clarifies which are the coral defense mechanisms. According to Cadavid, this will enable discovering strategies to control diseases within these ecosystems. 


This research project is product of a Sciences doctoral thesis funded by the Administrative Department for Science Technology and Innovation (Colciencias, for its Spanish acronym) and carried out by graduate student Iván Ocampo.