EnviroWeekly (Oct 13, 2010) As climate change increases; more coral reefs are at risk. The solution to recover the corals that are lost, seem further out of grasp. This statement is according to research done by Professor Mary Alice Coffroth and her colleagues at the University of Buffalo, published in PLoS ONE.
They are one of many mysterious organisms on the planet. Once mistaken as plants, corals are animals that are a part of the underwater world and an important aspect of its ecosystem. They contain limestone in their structure and tiny animals called polyps. The tiny polyps have tentacles that are used to catch plankton. Although plankton is a part of the coral’s diet, 98% of the coral’s food comes from the zooxanthellae. The zooxanthellae are a type of algae that cooperates with the coral reef in terms of survival. They are known as a symbiont, which are organisms that live off of each other, in this case, in a mutual way. The zooxanthellae use the coral reef for shelter and in return, it takes the coral's carbon dioxide waste and turns it into sugar. This is the coral’s main diet.
The coral reefs are of great importance for the environment and for our well-being. However, the coral reef population are declining worldwide. The cause of the disappearances is climate change. Due to global warming, the earth is heating up causing climate change to occur.
The increase in temperature of the water is causing a drastic effect. The corals are bleaching, where the flesh of the corals turns white from being deprived of nutrients. This term is not new; it has been around even before climate change became an issue. It is a natural cycle; however, bleaching has been increasing at a dangerous rate.When water temperatures increase the zooxanthellae cannot undergo photosynthesis and convert the carbon dioxide into sugars. These sugars are vital for the survival of the coral. Toxins begin to accumulate in the zooxanthellae and must be let go by the coral in order to survive. With the zooxanthellae, bits of the coral’s flesh breaks off causing the coral to turn white, or bleach.
Coral reefs are essential for the aquatic biodiversity. They provide shelter for many fish and other organisms, not to mention an abundant supply of nitrogen. Fisheries are dependent on coral reefs so they can obtain a large amount of fish to increase profits. Countries like Austrailia depend on the survival of coral reefs because they are a big attraction for tourists.
Mary Alice Coffroth, a professor at the University of Buffalo, and her colleagues of the Department of Geology, have experimented on the coral reefs and their relationship with symbionts. With their research they have proven that the coral reefs could recover as long as the algae could grow back and that climate change caused the disturbance. The original symbiont, zooxanthellae, was very stable and could withstand stress. Coffroth and her team tried to find a substitute alga that could work just as well, in order to recover the bleached coral. They observed that the coral could recover on its own with the help of a symbiont.
“For an adult coral to survive and subsequently recover after a bleaching event, the coral must either retain symbionts that can meet its minimum physiological requirements or acquire the necessary symbionts from the environment after bleaching.” (Coffroth et al 2010) This statement was in Coffroth’s research paper stating the solution to recovering the corals. Unfortunately, with this proposal, the biologists have not been successful in finding a symbiont that will be stress tolerable. Through their research and experiments, the team found that only the original algae, zooxanthellae, was stable enough. It is possible for the corals to obtain symbionts after bleaching and actually recover, however, there has yet to be a substitute symbiont that does not temporarily do the job. In Coffroth’s experiments, they used a substitute symbiont and after 5 weeks the population of the symbiont decreased immensely. 5 days before sampling, the symbiont was completely gone. The study does provide evidence that corals are flexible when it comes to obtaining algae and creating a symbiosis but only the natural symbiont works the best. Reason for temporary usage and the volatility could be from not being able to reproduce efficiently in the coral or having to fend off other symbionts.
To end speculation on whether climate change is the true cause of the bleaching and not another unbalanced variation in the ecosystem, Coffroth and her team focused on the symbionts reaction to induced heat. The heat killed off 98-99% of the population of zooxanthellae. The coral started to bleach but once the process was reversed and the temperature declined, the symbionts started to grow back. “Thus, these findings suggest that unless action is taken to curb global warming, the outcome of this will be a loss of coral reef biodiversity, leading to reefs that are very different from those that now exist.” (Coffroth et al 2010) The result of this research concludes that the greatest and efficient way of preserving the coral reef population is by controlling global warming.
Reference List:
Coffroth, Mary A., Daniel M. Poland, Eleni L. Petrou, Daniel A. Brazeau, Jennie C. Holmberg. 2010. Environmental Symbiont Acquisition May Not Be the Solution to Warming Seas for Reef-Building Corals. PLoS ONE 5(10). Web.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013258
"Coral bleaching – will global warming kill the reefs?" http://www.science.org.au/nova/076/076key.htm
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