Coral reefs and conservation Flashcards
how far does the distribution of corals reach?
Distribution defined by 20º C isother
What are the types of reefs?
attols and continental margins
How are sub reef habitats defined?
back reef and fore reef
there dends to be an area where there is a peak in diversity depending on disturbande -> wave energy and wave shock + light (IDH)
What are the two main types of corals
hermatiypic (reef building and generlaly with zooxanthellae) and ahermatypic (cup corals)
both reprocuce sexually
What are reef building corals?
- Phyla: Cnidaria
- Class: Anthozoan
- Order: Scleractinia
Reef building vorals are heratypic e.g. are colonial and have zooxanthellae
ahermatypic corals are solitary and have no zooxanthallae
explain the coral-zoocanthellae relationship
- photosyhtate translcated to coral host
- zopoxanthella photosynthesis results in increased rates of calcifiaction by the host
- zooxanthellae receive protection and essential nutrients from host
Benefits to zooxanthellae
- protection
- nutrients
- light
benefits for corals
-Removal of excretory products?
• Provide oxygen?
• Manufacture carbohydrates
• Enhance rates of calcification
• Lipid synthesis
How do coral reefs grow?
- Reefs consist of CaCO3secreted by plants and animals
- Slow process of precipitation moves the reef upwards and seawards
- Reefs provide structure and habitat diversity for other organisms
- Reefs are highly productive environments in generally unproductive waters (low nutrient concentrations)
- Recent evidence that calcification rates are dropping dramatically (De’ath et al Science 2010)!!
How do coral reproduce?
- asexual budding
- sexual reproduction (synchronous spawning event)
What physical factors affect coral growth?
- Co2
- pH
- ocean acidification
Why is ocean acidiciatio such a big threat to corals
How does the ecology of reef fish sustain coralls?
•Grazing
–Algae from overgrowing corals
–Prevents some corals dominating the reef
–Contributes to reef zonation& diversity
–Sediment budget
•Predation pressure on invertebrates & fish species contributes toward cryptic behavior & development of toxic passive defense mechanisms
How are coral reefs affected by catastrophic events?
- Early evidence suggested that complicated relationships and high diversity evolved over long periods
- Recent evidence suggests succession does occur and reefs can experience catastrophic mortality
- Connell’s intermediate disturbance hypothesis –compensatory mortality of dominant organisms allows co-existence of a diversity of organisms with similar requirements
- Crown of thorns (A. planci)
- colonize in massice recruitment events
- destroy entire reefs, (recovery > 10 years)
- El Nino events
Why do crown of thorns spread so rapidly?
Crown of thorns (A. planci)
- colonize in massice recruitment events
- destroy entire reefs, (recovery > 10 years)
•Causes?
–Release from predation pressure (triton shell Charonia, hump-headed wrasse, puffer fish)
–Larval survival (human induced?)
•Better food supply
•Warmer temperatures
•Favourablecurrents
What are the long term dynamics of coral reefs
- coral bleaching
- removal of fish (Jamica - 80% fish gone)
- What are main threats to coral reefs?
Bottom fishing/Overfishing
Pollution, sedimentation
Marine Invasions
Shifts in ecological integrity/assemblages
Climate Change (pH, Temperature, Storms)
What was a usefull tool when establishing MPAs in Queensland?
Engaging with the local fishers
