Coral Reefs
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Main ecological features
Located around the equator Shallow warm water - mid 20s High light availability Low nutrient water - slows algal growth Consistent salinity Low turbidity
What is a coral reef?
Made up of coral polyps Polyps secret calcium carbonate
What species are coral polyps ?
Cnidarians
How do coral polyps feed and get the energy they need to survive?
Tentacles and cilia - trap small particles Nematocysts - stinging cells to catch live prey Symbiotic relationship with zooxanthellae (photosynthesising algae) - the algae provides coral with oxygen and sugars, coral provides algae with CO2, phosphorus, nitrogen and a protective habitat
Importance of coral reefs to humans
Provide food Development of new medicines Carbon sequestration Cultural heritage Protect mangroves and sea grass meadows Provide jobs Provide coastal protection for over 500 million people Supports 25% of all marine species
Examples of medicines developed from coral reef species: coral
Used in bone grafts Secosteroids - used to treat asthma, arthritis and other inflammatory diseases
Examples of medicines developed from coral reef species: Sea Sponge
Antiviral drugs Treat HIV and AIDS
Examples of medicines developed from coral reef species: Indian Ocean Sea Hare
Dolastin 10 Cancer drug - inhibits cell division
Threats to coral reefs: Physical damage
Caused by; harmful fishing methods (e.g. bottom trawling), divers, coastal development Intentional and unintentional (tourism)
Threats to coral reefs: Pollution
Litter Oil spills Sewage Eutrophication
Threats to coral reefs: Introduced species
Escape from fish farms Ballast water - transfers organisms from different oceans
Threats to coral reefs: Collection of ornaments and souvenirs
Intentional removal of coral Made into jewellery Reduced by CITES - reduced trade
Threats to coral reefs: Coral Bleaching
Caused by temperature change Corals lose all colour - expel algae causing polyps to die High turbidity
Threats to coral reefs: Coastal development
Encroach onto coral reefs Increases pollution and turbidity More frequent boat activity Noise pollution
Threats to coral reefs: Sedimentation
Build of sediment caused by disturbing the sea bed Increases turbidity - slows photosynthesis of algae Runoff from coastal development
Threats to coral reefs: Fishing
Overfishing - fishing over maximum sustainable yield Destructive fishing methods - bottom trawling, ghost fishing, dynamite fishing
Threats to coral reefs: Loss of interdependent habitats (sea grass meadows and mangroves)
Disrupts life cycles Some species become extinct
Crown of Thorns Starfish Case Study
more fertile than any other invertebrates smothers and dissolves the coral usually kept in balance by pufferfish agricultural runoff = more larvae survive = algae grows faster (main food source) consume polyps = ecosystem collapses controlled by improving water quality, physical removal and biological controls
How do MPAs protect coral reefs?
manage overfishing support the control of threats protected from all extractive and destructive uses divers are educated
Example of MPA
Great Barrier Reef Marine Park established 1975 designated zones for different uses (recreational/research)
How are fishing controls helping coral reefs?
ban on bottom trawling and dynamite fishing no-take zones = stopped disturbances minimum/maximum catch size restrictions on net size quotas
Example of a coral reef that is recovering due to fishing controls
Great Barrier Reef - no take zones
What damage has been caused by tourism on coral reef systems?
pollution from boats wildlife disturbances pieces of coral snapped off for souvenirs increased stress causing coral bleaching
How are tourism activities being restricted to protect coral reefs?
maximum number of tourists that can visit a location educating tourists on their importance fixed moorings to stop ships dropping anchors