Coral Reefs - Part 3 Threats
- Created by: Lydia Sinclair
- Created on: 09-01-13 11:21
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- Threats to coral reefs
- Physical damage
- Swimmers, divers, boat anchors and litter
- Pollution
- Oils, pesticides and cyanide used illegally by some fishermen kill polyps
- Fertiliser run-off from farms causes eutrophication
- Souvenirs and ornaments
- 2000 species of coral are protected by CITES Appendix II but coral is still collected to sell as tourist souvenirs
- Fishing
- Overexploitation harms food webs
- Dynamite and cyanide used in fishing kills polyps
- Sediments
- Rivers carry sediments from eroding farmland, land reclamation projects and coastal developments to the sea. If it settles, it kills the polyps.
- Climate change
- If temperatures keep rising the polyps will expel their symbiotic algae, causing the reef to ‘bleach’. This results in poor food chains and are more sensitive to other damage.
- Sea-level rise mean that the symbiotic algae will not be close enough to the surface to photosynthesise
- A higher level of CO2 increases the water acidity which may dissolve the limestone that forms the reef
- Crown of Thorns Starfish
- A natural predator of the polyps, that's population is growing due to overfishing of it's predators
- Disease and predation
- Algae that grow on the surface of polyps (not the symbiotic algae!) provide sugars to bacteria that kill polyps
- Physical damage
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