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CORAL REEFSJulia Zapanta
Greg Saplagio III
CORAL REEFSOften called “rainforests of the sea”, they are one of the most diverse ecosystems on Earth. They occupy less than 0.1% (around 284,300 km2) of the world's ocean surface,
yet provide a home for 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, and other cnidarians.
They are most commonly found at shallow depths in tropical waters. Coral colonies thrive at 21-29OC, saline
environments, and clear waters.
LOCATION
Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and the Pacific) account for 91.9%.
CORAL TRIANGLEPHILIPPINES
TYPES OF CORAL REEFS
A fringing reef can take ten thousand years to form, and an atoll can take up to 30 million
years.
STRUCTURECorals are modular animals, anemone-like cylindrical polyps with prey-
capturing tentacles surrounding the opening or mouth. Most form sessile colonies supported on the tops of dead colonies and cease growth when
they reach the surface of the water
Coralline algae are important contributors to reef structure in those parts of the reef
subjected to the greatest forces by waves. These algae strengthen the reef structure by depositing limestone in sheets over the reef
surface.
ZONATIONGeneral abiotic conditions: Shallow waters, Temperature 21-29 C, Clear
low-nutrient waters, salinity 30-40 ppt.However, the coral reef can be divided into different zones with varying
abiotic characteristics and consequently different biological communities. The environmental factors responsible for these differences are wave action,
current direction and intensity, light intensity, etc.
Light sets the depth at which zooxanthellae can survive. Diversity is lowest at the crest near the surface, where only species such as massive pillar-shaped corals tolerant of intense or frequent disturbance of waves can
survive. Diversity increases with depth to a maximum of about 20 m. Then it decreases as light attenuates, eliminating shade-intolerant species.
Branching corals occur along the reef crest where abundant light drives photosynthesis needed to support rapid growth. Vigorous
wave energy clears sediment from the branching species that have no
biological means of sediment removal.
Further down the reef front, slower-growing hemispherical
corals (Mixed/Massive) are better suited for removing sediment
coming down the slope. In even deeper water, platelike colonies respond to continually
decreasing light levels. This shape places all the polyps on upward-facing surfaces, optimizing the
colony's ability to gather light—much like solar panels.
Adding to the productivity of the coral reefs are crustose, coralline algae, turf algae, macroalgae, sea grass, sponges, phytoplankton, and a large bacterial population. Coral reefs are among the most highly productive
ecosystems on earth.
This productivity and the varied habitats within the reef support a high diversity of life –thousands of kinds of invertebrates (some of which, such as sea urchins, feed on coral animals and algae), many kinds of
herbivorous fish that graze on algae, and hundreds of predatory species. Some of these predators such as the puffers and filefish, are corallivores, feeding on coral polyps. Others lie in ambush for prey in
coralline caverns. In addition, there is a wide array of symbionts such as cleaning fish and crustaceans that pick parasites and detritus from
larger fish and invertebrates.
SPECIES BIODIVERSITY
SOME ADAPTATIONS
SOME ADAPTATIONS
Threats to Coral Reefs
Natural and Human
REEFS WORLDWIDE ARE THREATENED
• 11% of reefs have been lost
• 16% of reefs severely damaged
• ~60% of studied reefs threatened by human activities
• No pristine reefs left
Threats to coral and coral reefs:• 1) Natural • 2) Anthropogenic –of human origin
Natural disturbances that affect corals and coral reefs?
• Hurricanes• Tsunamis• Volcanoes• Earthquakes• Predators &
competitors• Bleaching• Pathogens
Hurricanes
• Physical damage
• Destruction of other ecosystems upon which coral reefs depend
• Freshwater poisoning
• Smothering
Tsunamis
• Physical damage
• Possible disruption of reproduction and recruitment
• Erosion
Volcanoes
• Depends upon where volcano occurs
• Smothering and sedimentation
• Heat
Earthquakes
• Little direct impact
-coastal landslides
• Indirect impacts
-triggers tsunamis
Predators
• crown of thorns starfish
• snails• parrotfish• butterflyfish
Crown of Thorns Starfish
Coral-eating Snails
Competitors
• algae
• Loss of zooxanthellae
• causes – higher than usual
ocean temperature
– sharp changes in salinity
– heavy UV light exposure
Pathogens
• Diseases on the rise– new pathogens
(8+)– land pathogens
(Aspergillus)– occurring at all
depths–More
susceptible when stressed
Threats from Nature
• Unusually strong waves such as those from a hurricane
• Water temperature changes• Dramatic changes in saltiness of water• Predators, such as snails and crown of thorns
starfish• Overgrowth of algae
Threats to coral and coral reefs:• 1) Natural • 2) Anthropogenic –of human origin
Anthropogenic threats to coral
reefs:• Overfishing• Development• Mining and dredging• Recreation
Overfishing
• Ecological imbalance
Overfishing
• Ecological imbalance
Overfishing• Destructive fishing practices
Development
• Sediment smothering• Freshwater input• Pollutants & nutrients
(sewage, pesticides, fertilizer, heavy metals, pathogens)
Development
Development
Pollution
Power Plants
Mining for construction materials and dredging
• Destruction of reef structure• Stirs up sediment
Recreation
Anchors, boats, flippers, hands, feet•Kill animal tissue •Skeleton breakage
Threats from Humans
• Pollution– Sediments block light from zooxanthellae– Chemicals either poison corals or allow too much
algae to grow• Power plants– Filter water and kill fish and plankton– Releasing hot water kills organisms
More Threats from Humans
• Deforestation– Causes erosion which clouds the water– Burning of trees could be a factor in climate change
• Destructive fishing– Blasting with dynamite– Cyanide poison– Boats running aground, anchors– Overfishing
• interaction of natural changes & human activity
• multiple insults
Synergistic effects
Global climate change
• Reduced reef building• Increase in frequency and
intensity of hurricanes• Increases in bleaching• Increased in disease
A New Home
• Corals now have a choice of where to live
• Corals are very sensitive and are rapidly dying
• People are trying to help by creating artificial reefs
Arguments for Artificial Reefs• It can help
build or rebuild a reef
• It will increase fish populations by making new habitats
Arguments Against Artificial Reefs
• Moveable• Chemical leaking and
leaching into the ocean
• It does not increase fish populations but rather moves them to one location away from their natural habitat which makes them easier to catch
The Great Barrier Reef
Tubbataha Reef
It’s up to Us to Save Coral Reefs
Be Responsible.