ocn201bio12 corals slides - soest€¦ · •reefs are the foundation of incredibly complex...
TRANSCRIPT
• Domain
• Kingdom
• Phylum
• Class
Coral ClassificationEukarya
Animalia
Cnidaria
Anthozoa (Anemones and Corals)
Coral ReefsOCN 201 Biology Lecture 11
• Octocorals (8 tentacles, almost always colonial)
- Gorgonians, Soft corals, etc.
• Zoantharia (More tentacles, solitary or colonial)- Anemones, stony corals (reef building), black coral, etc.
Coral Types
Octocorals Zoantharia
Gorgonia Soft CoralBlack Coral
Stony Corals
Reef-Building Coral Polyp
Most reef-building stony corals have symbiotic zooxanthellae(photosynthetic dinoflagellates)
Calyx (or cup)
Zooxanthellae
• Coral Nutrition- Coral ingests small fish, zooplankton (protein/nitrogen)- Zooxanthellae photosynthesize (carbohydrate)
• Growth- Zooxanthellae assists in calcification- Calcification 10 x faster with zooxanthellae
Coral BleachingIf temperatures too warm, corals lose (or eject) the zooxanthellae
http://en.wikipedia.org/wiki/Coral_bleaching
• Polyp secretes calcium carbonate underneath
• Occasionally will lift up and create a new floor (basal plate), leaving a trapped space
• Carbonate deposition varies with temperature
Growth
• Age (# bands)
• Growth rate (band width)
X-ray of coral section
• Reproduction is frequently by synchronized broadcast fertilization (release of eggs and sperm into water)
• Fertilized eggs develop into larvae
• Many settle quickly, but can stay in plankton for 60 days or more - dispersal by currents
• Settlement is controlled by chemical cues
• Settled larvae develops into polyp and forms colony
Reproduction
• Reefs are the foundation of incredibly complex communities
• The reef provides structure that shelters diverse creatures and primary productivity that provides food
Coral Reef Habitat
• Found in tropical, nutrient-poor areas
• Where water temperature does not go below 18°C
• Higher diversity at western side of the ocean basins
Coral Reef Distribution
Coral ReefsAnnual Temp. Range <3°C
Distribution and Diversity of Stony Corals
Evolution of Island Reefs
Text
Time
Fringing
Eventually Atoll Drowns
Barrier Atoll
The Darwin Point
• Volcanic Islands ride the Pacific Plate northward into cooler waters
• Growth rate declines until it can no longer keep up with subsidence
• Critical Point (Darwin Point) is at about 29° North: Atoll drowns
The Darwin Point
Empe
ror
Seam
ount
Cha
inMidwayAtoll
Hawaiian Ridge
Hawaii
Darwin Point