Transcript Symbiosis between Zooxanthellae & Corals

Symbiosis between
Zooxanthellae & Corals
By
Mark Mergler
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
http://www.seaslugforum.n
et/factsheet.cfm?base=zoo
x1
http://plaza.ufl.edu/amb168
5/Coral_Reef.html
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
http://www.seasky.org/reeflife/sea2b.html
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

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
http://plaza.ufl.edu/amb1685/Coral_Reef.html
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
http://plaza.ufl.edu/amb1685/Coral_Reef.html
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
http://plaza.ufl.edu/amb1685/Coral_Ree
f.html
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
http://www.marinebiology.org/coralbleaching.htm
http://www.marinebiology.org/coralbleaching.htm
Climatic Change / Human
Impact
Climatic change

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
Increase in temperature
Violent weather
Increased UV exposure
Human impact

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Oil pollution
Coral mining
Overfishing
Sedimentation
Nutrient enrichment
References
Brown, 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.