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Assessing Coral Bleaching
Inquiry Activity A learning activity by Tom J. McConnell, Ball State University. Around the world, corals are "bleaching," a problem in which they lose their color. Coral bleaching is a sign of stress that can harm corals, and may even kill them. This problem is a symptom of a serious problem that can destroy entire coral reef ecosystems. In this activity, you will learn how scientists assess the degree of coral bleaching.
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You may have read about coral bleaching in the news or in Conservation Tales: Corals. But what is coral bleaching? Simply put, coral bleaching is what we call a loss of color in corals, eventually turning them white. But to really understand this, you need to know a bit more about corals. Corals are more than just a simple animal that lives in warm shallow waters and builds reefs by creating a stony skeleton. Healthy corals are actually a relationship between two kinds of organisms living together - an interaction we call symbiosis. Coral polyps (the individual coral organisms) live with a type of algae living inside their tissues! This algae is called "zooxanthellae." Learn more about the symbiotic relationship between coral and zooxanthellae The zooxanthellae are important in keeping the corals alive. These algae are photosynthetic - They make food from sunlight, water and carbon dioxide. Coral polyps CAN eat plankton (small organisms that float in the water), but they need the algae to help make more food in order to be healthy. Without zooxanthellae, coral polyps struggle to feed themselves, and may die. When corals are stressed by changes in temperature, cloudy water, disease or ocean acidification, they are likely to lose the zooxanthellae, and they "bleach" - they become pale and may eventually turn white! When scientists see corals beginning to bleach, they know they are not healthy. If the stressors can be removed, corals can re-gather more zooxanthellae and become healthy again. Learn more about coral bleaching and its causes
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For the Teacher Grade Level: 3-10 Time expected: 1 hour NGSS Standards Student Expectations
Connections to Nature of Science
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