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Threats to Coral Reefs
Natural and Human
Where Can You Find Coral Reefs?
Coral is found all over the world: Tropical Temperate Polar
Only tropical corals build reefs
Coral reefs around the world
Coral reefs around the world
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.