1. Symbiosis between Zooxanthellae & CoralsBy
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

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

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

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

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

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

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

17. References Brown, B. E. 1997. Disturbances to reefs in recent times
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)