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.