Losing Reef Diversity
We all know that biodiversity of a reef is important to the ecosystem. Yet, It is saddening to see that most of our coral reef are becoming unattractive and lifeless, You will hardly see the swaying of its colorful branches in current while the school of fishes swims through its leaves. When you start observing, you will see that corals has turned to white. The whitening of corals is a phenomenon known as coral reef bleaching. Its whitening is due to stress-induced expulsion or death of their symbiotic, zooxanthellae, or due to the loss of pigmentation within the protozoa.
Oceanographers see one of the major causes of coral reef bleaching is the effect of global warming. This stressful condition involves a breakdown of the symbiotic relationship between corals and unicellular flagellate protozoa called zooxanthellae. Other environmental triggers the changes of colors in the corals are changes in water chemistry (in particular acidification) prolonged exposure to air, especially during a very low tide, freshwater dilution due to heavy rainfall, intense sunlight causing increased ultraviolet radiation, pathogen infections, starvation cause by decline in zooplankton, changes in salinity, sedimentation, subaerial exposure during low tide, El nino southern oscillation caused sea levels to drop, tectonic uplifts, pollution and cyanide fishing are all causes of coral bleaching.
Zooxanthellae is a microscopic plant that lives within the coral tissue, giving food and color depending to their particular clade. Our coral reef has a chance to live and regain its original appearance. There are corals reefs that existed in the past geographical period even if the temperature is even warmer than today, However they become extinct during the start of ice age about two million years ago. It only shows that Corals are affected by the temperature variations. Large coral colonies such as Porities can adapt to extreme temperature while the fragile branching corals such as table corals that lives in a very narrow temperature range can not survive a slightest change in the seawater temperature, when there is an increase of 1-2 degrees for a period of weeks can cause bleeding. Another thing is, Corals that is consistently exposed to low stress levels may be more resistant to bleaching.
In 1996 they discovered that a bleaching agent of Oculina Patagonica was an infectious virus attacking zooxanthellae in the Mediterranean Sea.The bacteria were later identified as Vibrio shiloi. This is only infectious during warm periods. This bacteria penetrates the coral epidermis ,then it will multiply while producing heat stable and heat sensitive toxins, that affects zooxanthellae. The coral reefs of Mediterranean was said to gain resistance to the pathogen, Hypothesis emerge due to the presence of symbiotic communities of protective bacteria living in corals.
Global warming seems to be the main problem. It is very important to protect the reefs from dangers. A loss of coral will lead to a loss of our reef diversity, fishes will also lose their homes and there will be a decrease or even loss of fish production.
The future of the reefs are in danger right now and it is one of the major concerns of different organizations. They joined hands and put effort in stopping this from happening. However, it will take a long time to repair this damage. It is expected that by 2010-2040 period that corals will become highly susceptible to bleaching which IPPC see as the greatest threat to the world’s reef system.