Monday, March 17, 2014

Coral Bleaching & Disease

      Coral reefs support the worlds most biologically diverse marine ecosystems with many organisms relying on them for food and shelter. Nonetheless, coral reefs only cover a tiny fraction of the Earth's surface (less than 1%). Unfortunately, humans are a major threat to these ecosystems as our lifestyle brings devastation these diverse environments. Some of the threats caused by humans include pollution, destructive fishing, changing ocean chemistry, and last but not least, climate change. Due to the stressful conditions coral reefs are exposed to, they experience a phenomena called coral bleaching. Coral bleaching can be defined as a breakdown in the symbiotic relationship between coral and a unicellular algae (zooxanthellae). These algae live within the corals to help them grow and obtain food. When stresses, such as thermal stress arises, the corals will expel their zooxanthellae giving them a characteristic bleached appearance. Other stresses such as high light intensity, low salinity, and pollution are also linked to coral bleaching and the presence of coral diseases.


     In reviewing an article by Ove Hoegh-Guldberg on coral reef ecosystems and anthropogenic climate change, he suggests that our current levels of carbon dioxide in the atmosphere are much too high to ensure the survival of coral reef ecosystems. I will further explore his interpretations of coral bleaching and microbial infections. Furthermore, I will investigate the idea that corals have different susceptibilities to different stresses, meaning the devastation of one species of coral does not mean devastation for all. The remainder of the article will be analyzed to see how much devastation coral reefs can take and the implications of the loss of coral-dominated reef systems.
     
     My analysis of another paper on the conditions of coral reefs in south Florida will include a presentation of percentages of coral reefs that are diseased and bleached to help indicate the condition of this ecosystem. This paper also looks at different diseases that affect corals and shows which diseases are most prevalent in southern Florida coral reef communities. The authors of this study found large amounts of coral devastation in the Florida Keys which will be analyzed in further detail in the research paper. 

     A final paper I will analyze studies the influence of habitat devastation (dead and/or bleached corals) on fish replenishment. More specifically, the fragmentation and degradation of marine ecosystems such as coral reefs due to anthropogenic climate change are expected to have devastating effects on the organisms that call coral reefs home. By monitoring daily fish settlement patterns, the authors of this article found that fish were ten times more likely to settle on healthy coral than bleached/dead coral. Further examination of this article will show that coral bleaching will affect the settlement of reef fish, reef organism distribution, and population dynamics.

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