Download Coral Reefs

Coral
Reefs
Coral reefs are warm, clear, shallow
ocean habitats that are rich in life.
Coral reefs are among the most
biologically diverse regions on Earth.
Even though they cover only a tiny
fraction (less than .2 percent) of the
ocean's bottom, coral reefs contain more
than 25 percent of all marine life.
What is coral?
• Coral are cousins to jellyfish and
anemones (Cnidarians)
• Corals (tiny animals, called
polyps) secrete a stony cup of
limestone around themselves as a
skeleton
• The polyp absorbs calcium
carbonate out of the water and
use the calcium carbonate to
build the reef
• Millions of polyps work together
in a cooperative colony generation
after generation to create the
limestone skeletons that form
the framework of the coral reef.
• Have been in existence about 200
million years.
2 Types of Reproduction:
Asexual and Sexual Reproduction
• Asexual reproduction in
corals is called budding.
• Sexual reproduction is
called spawning.
This is a hydra (cousin to coral)
with two buds. One bud (on the
right) is older than the other.
How Do Corals Eat?
Option One: Mutualistic Relationship
• Inside polyps live zooxanthellae (algae).
• Zooxanthellae give corals their color and can
provide food.
• Since algae are plants, they photosynthesize. This
gives off oxygen as a by-product
that is used by the host polyp.
• Coral provide the algae with
carbon dioxide and a safe,
protected home.
How Do Corals Eat?
Option Two:
• Soft bodied carnivores with stinging tentacles around their
mouth.
• Coral polyps come out of their skeletons to feed, catching
tiny floating animals known as zooplankton.
• Tentacles release stinging cells (nematocysts) when
something brushes by them, stunning the food and
bringing it back towards the mouth.
Essentials of Coral Reefs
Warm Water:
• Grow mainly in warm tropical areas (ideally
between 70-85°F) between Tropic of Cancer
and Tropic of Capricorn.
• Most diverse is the Great Barrier Reef in
Australia - over 3000 different plants and
animals.
Essentials of Coral Reefs
• Sunlight: Corals need to grow in shallow water
where sunlight can reach them. Corals rarely
develop in water deeper than 165 feet (50 m).
• Clear Water: Corals need clear water that lets
sunlight through to survive.
• Salt Water: Corals need saltwater to survive and
require a certain balance in the ratio of salt to
water. This is why corals don't live in areas where
rivers drain fresh water into the ocean.
Essentials of Coral Reefs
Clean water:
• Corals are sensitive to pollution and sediments.
• Sediments can settle on coral, blocking out sunlight
and smothering coral polyps.
• Pollution from sewage and fertilizers increase
nutrient levels in the water, harming corals.
Types of Reefs
• Fringing Reef – lie around islands
& continents
• Barrier Reef – grow on the edge
of continental shelves and also
are separated from shorelines by
lagoons
• Atolls – a central lagoon and are
circular or sub-circular. Formed
from subsiding underwater
volcano (seamount).
Why are reefs important?
• Biodiversity
• As a food resource
• Source of economic wealth
• Medicinal use
Why are reefs important?
• Medicinal use:
Coral reefs are sometimes considered the
medicine cabinets of the 21st century.
Coral reef plants and animals are important
sources of new medicines being developed to
treat cancer, arthritis, human bacterial
infections, Alzheimer’s disease, heart
disease, viruses, and other diseases.
In the future, coral reef ecosystems could
represent an increasingly important source of
medical treatments, nutritional supplements,
pesticides, cosmetics, and other commercial
products.
Threats: Coastal Development
• Dredging
• Construction
materials
• Building on
reefs
• Unregulated
tourism
Threats: Tourism/Recreation
• corals easily broken by trampling when people walk
out to the reef
• snorkelers and divers may kill polyps simply by
touching coral colonies
• debris left from tourists
Threats: Marine Pollution
• Oil spills and
discharge of oily
ballast water
• Large power plants
change water
temperatures by
discharging
extremely hot water
into the coastal
water.
Threats: Inland Pollution
• Erosion from
increased forest
clearing & intense
agriculture causes silt
to wash into water,
clouding it, and
suffocating the coral.
• Sewage & agricultural
fertilizer runoff
increases nutrients in
ocean, which produces
more seaweed that
hurts the coral.
Threats of Coral Bleaching
• Greenhouse Effect - may cause increases in sea
temperature
• Sea water that becomes too warm causes corals to
turn white, or bleach; a reaction that occurs if
coral polyps are stressed.
http://www.youtube.com/watch?v=aEdoizgeNJk
Threats: Overfishing
• Removal of reef fish causes ecosystems to be unbalanced.
• Due to decreased yields, fishermen forced to change
methods to catch enough fish to sustain needs:
• Fishing with cyanide
• Blast Fishing
**Not only do these practices kill all fish in the affected
areas but they also severely damage the corals.
Threats: Overexploitation
• Corals are popular as decorations, jewelry, and
souvenirs.
• Coral is also mined: Used to build houses and make
roads, or is burnt to make lime.
• Used in aquariums.
Threats: Natural Disturbances
• Destroyed by hurricanes
and tropical storms.
• Diseases, such as blackband disease – spreads over
colonies, progressively
killing the polyps.
• The crown-of-thorns sea
stars feeds on corals, if
many, can reduce a reef to
a mass of dead coral
skeletons quickly.
http://videos.howstuffworks.com/discovery/30523-onestep-beyond-crown-of-thorns-starfish-video.htm
Disturbing Facts
• 58% of the world’s reefs
are at risk from human
activities
• 90% of reefs are overfished
• Almost two-thirds of
Caribbean reefs are
threatened
• 40 countries contain no
protected reef areas
Preserving Coral Reefs
http://www.youtube.com/watch?v=Jn5-ARXmQlQ