Tropical Reefs: CoralAlgal

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Tropical Reefs Coral/Algal

• Diversity and Challenges

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Questions

• Why are tropical reefs comparable to rain forests
  in diversity?
• Dissolved nutrients are scarce
• Productivity diversity normally go together
• Why are tropical reefs disappearing?

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Increasing threats to coral
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Tropical reefs are geologically important
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Reef ecology has long challenged biologists
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Dominant reef-building organisms

• Small individuals, magnified in effect by large
  numbers
• Phylum Cnidaria
• Class Anthozoa
• Subclass Zoantheria
• Diverse algae, depositing CaCO3

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Cnidaria polyps radial symmetry
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Cnidaria tentacles for feeding
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Cnidaria stinging cells on tentacles
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Not all corals deposit CaCO3
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Hermatypic corals create reefs in symbiosis
with Symbiodinium
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Growth forms of colonies reflect tradeoffs

• Access to light for symbiotic algae
• Issues of depth (growth upward)
• Issues of competition (shading)
• Risk of damage from turbulence in shallow seas
• Diverse growth forms reflect different balances

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Fast extension linear growth form
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Extension more surface area branching
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Lattice a subset of branching form
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Plate form more resistant to turbulence
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Massive form very wave-resistant
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Independent algae build reefs crustose
Algae can contribute a large fraction of reef mass
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Independent algae Green (Halimeda)
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Reefs a matrix of solid coral and sand
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Reef diversity some examples
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Ecological functional groups
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A larger scale view reef building process
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Atoll structure
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Habitat diversity within an atoll
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