Ecology of Coral Reefs

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Feb 22, 2014 (3 years and 1 month ago)

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Ecology of Coral Reefs

Spring 2012

Mariana
Freitas


Introduction


Coral reefs are unique ocean ecosystems in
that they have extremely high productivity
and
diversity.


Also called tropical


rain forests of the


ocean because of


their diversity.


Phylum
Cnidaria


Corals are part of a group of small aquatic
animals called “Cnidarians”. Other Cnidarians
are sea anemones, hydroids and jellyfish.


Corals are a very diverse group and they are
made up of many tiny organisms living
together in a colony, and each individual
organism is called a “polyp”.

Importance of Coral Reefs


Home to numerous organisms


Protection and shelter


Increase
the
diversity


Food


Control of carbon dioxide


Barrier to coasts and shore


Environmental Conditions


Certain conditions are necessary in order for a
coral reef to form.



Temperature
, light, salinity, sedimentation and
wave energy all play a crucial role in reef
development.



Reefs grow best in sunny, shallow, clear water.

Environmental Conditions


Temperature

-

minimum temperature of
18
°
C
and
a maximum temperature of
32
°
C


Shallow



bordering land at depths of less
than 27 meters


Clear



sunlight necessary for
zooxanthellae

to
perform photosynthesis


Salinity

-

require a salinity between 34 and 37
parts per 1000


Types of Reefs


There are three kinds of coral reef: the
fringing reef, the barrier reef and the atoll.


Fringing reef


develop in shallow waters
along the coast of tropical islands or
continents. They grow right up to sea level.


Types of Reefs


Barrier reef


separated from the shore by a
wide, deep lagoon.
They grow only when
there has been a change of sea level on the
adjacent coast
.


Types of Reefs


Atoll



circular reef surrounding a lagoon.



Reproduction


Corals can reproduce both sexually and
asexually.


Asexually reproduction may occur by budding
or fragmentation.


Sexually reproduction occurs either by internal
or external fertilization.


Some corals are hermaphroditic (both female
and male reproductive cells).


Zooxanthellae


Symbiotic relationship with corals in which both
organisms benefit from each other.


Zooxanthellae

is an unicellular algae that lives in
the
gastrodermis

of reef building corals.


The algae supplies oxygen and other nutrients
that allow corals to grow and reproduce.


Corals give carbon dioxide and other substances
that algae needs.

Diseases


Coral diseases

can occur
in response to biotic
stresses

or
abiotic

stresses.


The rate of incidences has been increasing
rapidly over the last 10 years.


Some of the causes include poor water quality
(human pollution) and increase of surface
temperatures.

Diseases


Black
-
band disease
(BBD)
-

blackish concentric
or crescent
-
shaped
band;
cyanobacteria

has
been primarily associated with this disease
and also sulfide
-
oxidizing bacteria.

Diseases


White band disease
(WBD)


complete
degradation of coral tissue in Caribbean
acroporid

corals. Usually proceeds from the
base of colony to branch tips.

Diseases


White plague


similar to WBD; sharp
line
between apparently healthy coral tissue and
freshly exposed coral
skeleton.

Diseases


White pox


white circular lesions; tissue
degradation occurs rapidly.


Yellow band
-

large rings or patches of
bleached

yellow tissue; loss of tissue is slow.


Dark spots


dark, brown
or
purple
pigmented
areas; tissue loss is minimal.


Threats and Destruction


Both natural and human related causes.


10% of the world’s coral reefs have already
been destroyed.


Scientists predict that in the next 20
-
40 years,
70% of the coral reefs will be lost, if no
changes are made by human population.

Threats and Destruction


G
lobal warming


Overfishing


Tourism


Water contamination


Increase CO2


Conclusion


Coral reef ecosystems are one of the most
valuable ecosystems on Earth.


They are incredibly diverse, very productive,
but also extremely fragile.


They provide food, protection of coasts, and
shelter to many marine organisms.


Serious threats include climate change, fishing
and pollution.

References


http://oceanworld.tamu.edu/students/coral/coral5.htm


http://plaza.ufl.edu/bettie/coralreef.html


http://coris.noaa.gov/about/diseases/


Introduction to the Biology of Marine Life,
Ninth Edition by John F.
Morrissey and James L.
Sumich


Ecology: The Experimental Analysis of Distribution and
Abundance
,
Sixth Edition by Charles J. Krebs


Marine Ecology: concepts and applications,

by Martin Speight and
Peter Henderson


Marine Ecology
, Oxford by Sean D. Connell and Bronwyn M.
Gillanders


Marine Community Ecology
, First Edition by Mark D.
Bertness
,
Steven D. Gaines, Mark E. Hay