Rocky and coral reefs Flashcards
Hermatypic corals
Reef-building
Secrete CaCO3
Colonial and large number of zooxanthellae
Divided in: massive and brancing forms
Ahermatypic corals
Non-reef building
Worldwide and in deep sea
Factors limiting reef growth
Temperature Light availability Salinity Turbidity Sedimentation Sea level fluctuation Bioerosion by grazers and borers
Coastal reefs are divided into:
Fringing reef
Patch reef
Barrier reef
Barrier reef
Typical in tropical islands and are separated from coast by a lagoon.
Fast growth in lower zone
Fringing reef
Common in beaches where rocks are available for coral growth
Grow up to the surface and then extend horizontally
Patch reef
Common in lagoons
Atolls
Explosive volcano disappears and contour remains, which is filled by water, forming a lagoon
Coral reef growth upset by:
Climate change
sedimentation
fishing
pollution
Rocky reefs are divided into:
Intertidal and subtidal zone
Rocky reef intertidal zone is dominated by
Individuals (mussels, barnacles, limpets)
Subtidal zone is dominated by:
Colonial animals
But also include individual species
Colonial forms are more common in subtidal zone because:
Do not have the ability to live without water (dessication)
Do not tolerate salinity differences
More resistant to predation and competition
Competitive interactions properties:
Space occupation Rapid growth Larger colonies are more competitive Unpredictable outcomes due to varied competitive mechanisms Priority effect on bare surfaces
Why do rocky reefs have a nursery function?
Junvenile fishes can grow
Food availability and protection from predators
Why do rocky reefs have a nursery function?
Junvenile fishes can grow
Food availability and protection from predators
What determines prominent depth zonation?
Wave and current strength, light and suspended sediments
Competition: dominance and overgrowth
What is mutualism?
symbiotic relationship where all species involved benefit from their interactions
Predation defense of coral reefs
1) Chemical defenses
2) Camouflage or nocturnal activity
What are the main biological interactions and community structure of coral reefs?
1) Higher complexity and diversity of competition slows down dominance of one species
2) Herbivores have strong effect on species composition
3) Strong top-down effects (predator controls abundance of rest of the species)
What are major threats to coral reefs?
1) Human impact
2) Direct: sedimentation, pollution, diseases, tropical storms
3) Indirect: increased nutrients and overfishing, climate change
4) Thermal stress can cause mass bleaching
Reefs and human society
1) Source of food and income
2) Economic benefit but also anthropogenic stress
3) ecosystem service: coastal defense
