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Symbiosis between Zooxanthellae & Corals
By
Mark Mergler
What are Zooxanthellae?Unicellular yellow-brown dinoflagellate algae which live in the gastrodermis of coralsProvide corals with food in the form of photosynthetic productsLive in coral’s tissues at a density of 1million cells/cm² Due to need for light, they only live in ocean waters <100 mRecently found that there are 10 different species that live in corals
http://plaza.ufl.edu/amb1685/Coral_Reef.html
http://www.seaslugforum.net/factsheet.cfm?base=zoox1
What are Corals?Start their lives as free-swimming youngOnce they find a hard bottom, they attach themselves and quickly change into a polypCoral polyp splits in 2 and makes an identical copy of itselfForm a colony and secrete a hard calcium carbonate skeletonEach polyp makes a small skeletal cup called a calyx which aids in feedingAs coral colony grows, it secretes new skeletal material on top of the oldOver thousands of years of accumulation, a coral reef is formed
http://www.seasky.org/reeflife/sea2b.html
Symbiotic Relationship between the Two
ZooxanthellaeProvide Corals with food in the form
of organic matter
CoralsProvide zooxanthellae a safe place to
liveExcrement is taken in by
dinoflagellates and are recycled
Fringing Reefs
Simplest & most common typeDevelop near shore throughout tropicsOccurring close to land makes them vulnerable to sedimentation, freshwater runoff, and human disturbance Consist of An inner reef flat An outer reef slope
http://plaza.ufl.edu/amb1685/Coral_Reef.html
Barrier Reefs
Much further from shore than fringing reefConsist ofA back-reef slopeA reef flatA fore-reef slope
Most coral growth occurs on the fore-reef slope
http://plaza.ufl.edu/amb1685/Coral_Reef.html
Atoll
Ring of reef that form from sinking volcanoesUsually have a central lagoonCan rise up from depths of thousands of meters or moreOccur mostly in the Indo-west Pacific region
http://plaza.ufl.edu/amb1685/Coral_Reef.html
Coral Bleaching
Occurs when corals undergo stressful situationsWhite calcium carbonate skeleton is exposed when corals expel their zooxanthellaeNever a total elimination, (60-90%) remain Is possible for corals to come back as long as a substantial amount of time has not passedNormal environmental conditions must returnIf conditions do not return, host corals will perish
http://www.marinebiology.org/coralbleaching.htm
http://www.marinebiology.org/coralbleaching.htm
Climatic Change / Human Impact
Climatic change Increase in temperature Violent weather Increased UV exposure
Human impact Oil pollution Coral mining Overfishing Sedimentation Nutrient enrichment
ReferencesBrown, B. E. 1997. Disturbances to reefs in recent times. Pages 354-379 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, 2000.
Hughes, Terry P. “Climate Change, Human Impacts, and the Resilience of Coral
Reefs” Science. 301.5635 (2003) 564-576.
Muller-Parker, G., and C. F. D’Elia. 1997. Interactions between corals and their symbiotic algae. Pages 96-113 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. 17.4 (2003) 956-967.