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Assessing Coral Bleaching
Inquiry Activity A learning activity by Tom J. McConnell, Ball State University. |
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Just what is a coral?
According to Dr. Kourtney Klepac, a coral restoration researcher, corals can be described a rock, an animal, a plant and a complex interaction of many organisms. Symbiosis, Corals and Zooxanthellae In this activity, we can think of corals as symbiotic relationship between a coral animal and an algae called zooxanthellae. This relationship is an example of "mutualism," a symbiotic relationship in which both species benefit. The algae benefit from having a place to live that includes a calcium carbonate skeleton to provide a structure that can keep it in a place where it gets sunlight and has protection. In turn, the algae creates food through photosynthesis that can feed the coral animal when other food is scarce. Coral Polyps Coral is a simple animal that consists of small polyps. Coral are animals in the phylum Cnidaria, a group that includes jellyfish and sea anemones. Cnidarians that attach to a surface are called polyps. Cnidarians that swim in the water are referred to as medusa. Both medusa and polyp forms have tentacles with stinging cells called nematocysts that paralyze and capture food that they digest in a simple gut. While they can feed themselves, coral sometimes struggle to provide enough food for each polyp to survive. They live in colonies that can include millions of individual polyps, each creating a hard calcium carbonate skeleton that forms the shapes you think of when you picture a coral. Coral Bleaching Each polyp is clear - it has no color of its own. The colors we see in corals come from the different kinds of zooxanthellae that can live in their tissues. When corals are stressed, they can eject these zooxanthellae. Scientists are still trying to study how and why they do this. Bleaching is a symptom of a problem in the environment that could kill the corals. Learn more about coral bleaching In order to diagnose these problems early, scientists assess the health of coral by looking for the early stages of bleaching. |
Close-up of coral polyps. (Ryan, 2006. CC-BY-NC 2.0. https://flic.kr/p/tNN3t
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