Week 12: Coral reefs Flashcards
Coral reef community
Most diverse ecosystem on planet
What is a coral reef?
Consist of a living framework w internal cavities filled w sediment and a surrounding area of reef-derived skeletal grains
High energy environment- 1st to obtain nutrients
*Abiotic structure created by biotic means
Three main types of coral reefs
- Fringing reefs
- Barrier reefs
- Atolls
Fringing reefs
Non existent or shallow back reef zone, may connect directly to land
Located nearshore
Most common
ex.Ningaloo reef in west australia
Barrier reefs
Separated from land by a deep channel or lagoon
Outer edge is raised for food supply and to grow quickly
ex.great barrier reef
Atolls
Ring shaped island of coral reefs and coral debris
Encloses a shallow lagoon
Darwin and reef development
Believed it was a consistent pattern from fringing to barrier to atoll
BUT WRONG
Didnt account for sea level rise
Who builds the reef (part 1)?
Phylum Cnidaria - corals, sea anemones and jellies
All have specialized cells (cnidocytes) for protection and capturing prey
2 basic body forms of cnidaria
- Free swimming/floating medusa ex. jellies
- Sessile polyps ex. corals
How do cnidaria sting?
Their cnidocytes (stinging cells) contain nematocysts
How do cnidaria reproduce?
Sexually and asexually
Who builds the reef (part 2)?
Hermatypic corals contain tiny plant like organisms living in their tissue (zooxanthellae)
Zooxanthellae
Tiny photosynthetic algae living in tissue of most corals
Mutualism- coral supply nutrients, zooxanthellae supply food
Who builds the reef (part 3)?
Scleractinla (order)- stony or hard corals
Create a hard calcareous skeleton
Secrete aragonite
Who builds the reef (part 4)?
Coral polyp (stomach, tentacles and mouth)
Secretes CaCO3 to build hard outer skeleton
What type of organism are reef corals?
Mixotrophs
Energy needs of coral
10% from food capture
90% from zooxanthellae
What type of water is coral most efficient in?
Oligotrophic environments (nutrient poor)
Ensures adequate sunlight bc it isnt blocked
Ideal conditions for reef growth
Clear(nutrient poor), brightly lit, warm, shallow water, normal-slightly elevated salinity, strong wave activity to bring nutrients in
Ideal temp for coral growth
25-29 degrees celsius
Ideal salinity for coral growth
25-35 %
What happens if there is drastic change in conditions for coral?
Zooxanthellae leave and it causes a coral bleaching event
Horizontal zonation of coral reefs
Reef front (reef slope)
Reef crest
Reef flat
Back reef (lagoon)
Vertical zonation of coral reef
Deeper= less light , less wave energy, reduced diversity
