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Coral Reefs
http://www.enchantedlearning.co
m/subjects/ocean/Coralreef.shtml
Coral reefs are warm, clear, shallow ocean
habitats that are rich in life
• The reef's massive structure is
formed from coral polyps, tiny
animals that live in colonies;
when coral polyps die, they
leave behind a hard, stony,
branching structure made of
limestone.
• Coral reefs develop in shallow,
warm water, usually near land,
and mostly in the tropics; coral
prefer temperatures between 70
and 85 ° F (21 - 30 °C).
Types of Reefs:
1. Fringing reefs are reefs that form along a coastline. They grow on
the continental shelf in shallow water.
2. Barrier reefs grow parallel to shorelines, but farther out, usually
separated from the land by a deep lagoon. They are called barrier
reefs because they form a barrier between the lagoon and the
seas, impeding navigation.
3. Coral Atolls are rings of coral that grow on top of old, sunken
volcanoes in the ocean. They begin as fringe reefs surrounding a
volcanic island; then, as the volcano sinks, the reef continues to
grow, and eventually only the reef remains.
1. Fringing Reef: Polynesian island of Mooréa
2. Barrier Reef
http://images.google.ca/imgres?imgurl=http://www.edc.uri.edu/lme/Images/neaustralian/atoll.jpg&imgrefurl=http://www.edc.uri.edu/lme/Text/neaustralian.htm&h=171&w=230&sz=18&tbnid=QiomFYTx9sIJ:&tbnh=76&tbnw=102&start=18&
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The Great Barrier Reef
(off the coast of NE
Australia) is the
largest coral reef in
the world. It is over
1,257 miles (2000
km) long.
3. Tuanake Atoll in French Polynesia
What are coral polyps?
• Coral polyps are small marine
invertebrate animals. Most
polyps live in large colonies.
• There are two types of
corals:
– Hard corals: secrete
calcium carbonate skeleton
(forms the reef when the
coral polyp dies)
– Soft corals
• http://response.restoratio
n.noaa.gov/oilaids/coral/t
our/tour.html
Great Star Coral: each polyp is about 1cm in diameter
1). The mouth is surrounded by
tentacles armed with stinging
cells for capturing plankton.
During the day these tentacles
are folded in the digestive sac.
2). Microscopic single-celled algae
that give the coral its green,
blue or brown colour are
located in the tissue of the
living coral.
(3). These symbiotic algae
(Zooxanthellea) process the
wastes produced by the polyps.
Through photosynthesis they
generate oxygen and organic
compounds which the polyps
themselves can use. They may
also help the polyp lay down
calcium carbonate.
Corals are carnivorous!!
• Corals are carnivores that eat zooplankton (like copepods
and tiny marine larvae). They catch food using tentacles
that surround the mouth; the tentacles have poisonous
stingers (called nematocysts)
• Zooplankton: Small animals that generally have limited or no
swimming ability and are transported through the water by currents
and tides
examples: amphipods, shrimp, fish larvae, copepods,
invertebrate larvae, protozoans and rotifers
Coral reproduction:
• Corals reproduce either asexually (the polyp
grows another polyp out of its side) or sexually
(polyps can be male, female, or male and
female)
Predators
Corals are eaten by the
crown-of-thorns (a
large starfish that eats
coral polyps),
parrotfish, and other
animals.
Threats to Coral Reefs:
1. Human Contact: Touching Reefs, even slightly, can harm them. Boats
and dropped anchors can cause severe damage to these fragile
ecosystems. Frequent human contact kills the reefs over time.
2. Runoff Water: Silt from eroded soil in runoff water can block sunlight.
Without sunlight, photosynthesis does not occur and reefs gradually die.
3. Sewage: Untreated or improperly treated sewage promotes the growth of
algae, which harms coral reefs.
4. Cyanide Fishing: Some fishermen stun fish by squirting cyanide, a very
toxic poison, into reef areas where fish seek refuge. The poison does not
kill, but disorients the fish in the coral where they hide. The fisherman
then rip apart the reefs with crowbars to capture the fish. In addition,
cyanide kills coral polyps and the symbiotic algae and other small
organisms necessary for healthy reefs. Cyanide fishing is common in the
South Pacific and Southeast Asia.
5. Fertilizers & Pollution: Fertilizer runoff, pesticides and other chemicals
can poison reefs.
6. Blast Fishing: Shock waves from blast fishing can destroy coral reefs.
7. Increased UV rays: causes coral bleaching (when the zooxanthellae die
and leave the coral white.
Coral reefs: importance
• Tropical coral reefs are very productive
ecosystems.
• Not only are do they support enormous
biodiversity, they are also of immense
value to humankind.
• Latest estimates suggest coral reefs
provide close to $30 billion each year in
goods and services
Coral reefs: importance
1. Fisheries: Coral reefs are vital to the world’s fisheries. They form the
nurseries for about a quarter of the ocean's fish, and thus provide
revenue for local communities as well as national and international
fishing fleets. An estimated one billion people have some dependence
on coral reefs for food and income from fishing. If properly managed,
reefs can yield around 15 tonnes of fish and other seafood per square
kilometre each year.
2. Tourism: Tourism revenues generated by coral reefs are also
significant. For example, according to a report by the Key West
chamber of commerce, tourists visiting the Florida Keys in the US
generate at least US$3 billion dollars in annual income, while
Australia’s Great Barrier Reef generates well over US$1 billion per
year. Sustainably manged coral reef-based tourism can also provide
significant alternative or additional sources of income to poorer
coastal communities in developing countries.
Coral reefs: importance
3.Coastal protection: Coral reefs break the power of the
waves during storms, hurricanes, typhoons, and even
tsumanis. By helping to prevent coastal erosion, flooding,
and loss of property on the shore, the reefs save billions of
dollars each year in terms of reduced insurance and
reconstruction costs and reduced need to build costly
coastal defences - not to mention the reduced human cost
of destruction and displacement.
Coral reefs: importance
4. Source of medical advances: We can also expect coral reef
species to contribute to future medical advances. Already coral
reef organisms are being used in treatments for diseases like
cancer and HIV. Just as with tropical forests, we may continue
to find the answers to medical problems in the coral reefs - so
long as we can keep them healthy.
5. Intrinsic value: For many coastal societies around the world,
coral reefs and their inhabitants are intricately woven into
cultural tradtions. For these people - as well as for those who
have floated with a mask and snorkel, immersed themselves in
the three dimensional wonderland of a scuba dive, or
experienced these habitats through media and books - a world
without coral reefs would be an infinitely poorer place.
Reef Diversity
• http://www.enchantedlearning.
com/biomes/coralreef/coralree
f.shtml