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Symbiosis between Zooxanthellae & Corals By Mark Mergler.

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Presentation on theme: "Symbiosis between Zooxanthellae & Corals By Mark Mergler."— Presentation transcript:

1 Symbiosis between Zooxanthellae & Corals By Mark Mergler

2 What are Zooxanthellae? Unicellular yellow-brown dinoflagellate algae which live in the gastrodermis of corals Provide corals with food in the form of photosynthetic products Live in coral’s tissues at a density of 1million cells/cm² Due to need for light, they only live in ocean waters <100 m Recently found that there are 10 different species that live in corals

3 5/Coral_Reef.html et/factsheet.cfm?base=zoo x1

4 What are Corals? Start their lives as free-swimming young Once they find a hard bottom, they attach themselves and quickly change into a polyp Coral polyp splits in 2 and makes an identical copy of itself Form a colony and secrete a hard calcium carbonate skeleton Each polyp makes a small skeletal cup called a calyx which aids in feeding As coral colony grows, it secretes new skeletal material on top of the old Over thousands of years of accumulation, a coral reef is formed

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6 Symbiotic Relationship between the Two Zooxanthellae Provide Corals with food in the form of organic matter Corals Provide zooxanthellae a safe place to live Excrement is taken in by dinoflagellates and are recycled

7 Fringing Reefs Simplest & most common type Develop near shore throughout tropics Occurring close to land makes them vulnerable to sedimentation, freshwater runoff, and human disturbance Consist of An inner reef flat An outer reef slope

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9 Barrier Reefs Much further from shore than fringing reef Consist of A back-reef slope A reef flat A fore-reef slope Most coral growth occurs on the fore-reef slope

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11 Atoll Ring of reef that form from sinking volcanoes Usually have a central lagoon Can rise up from depths of thousands of meters or more Occur mostly in the Indo-west Pacific region

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13 Coral Bleaching Occurs when corals undergo stressful situations White calcium carbonate skeleton is exposed when corals expel their zooxanthellae Never a total elimination, (60-90%) remain Is possible for corals to come back as long as a substantial amount of time has not passed Normal environmental conditions must return If conditions do not return, host corals will perish

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16 Climatic Change / Human Impact Climatic change Increase in temperature Violent weather Increased UV exposure Human impact Oil pollution Coral mining Overfishing Sedimentation Nutrient enrichment

17 References Brown, B. E Disturbances to reefs in recent times. Pages in Life and Death of Coral Reefs, edited by C. Birkeland. Chapman & Hall, New York, NY. Graham, Linda E., and Lee W. Wilcox. Algae. Upper Saddle River, NJ: Prentice Hall, Hughes, Terry P. “Climate Change, Human Impacts, and the Resilience of Coral Reefs” Science (2003) Muller-Parker, G., and C. F. D’Elia Interactions between corals and their symbiotic algae. Pages in Life and Death of Coral Reefs, edited by C. Birkeland. Chapman & Hall, New York, NY. West, Jordan M., and Rodney V. Salm. “Resistance and Resilience to Coral Bleaching: Implications for Coral Reef Conservation and Management.” Conservation Biology (2003)


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