Tropical Reefs: Coral/Algal
description
Transcript of Tropical Reefs: Coral/Algal
Tropical Reefs: Coral/AlgalTropical Reefs: Coral/Algal
Diversity and ChallengesDiversity and Challenges
Questions:Questions:
• Why are tropical reefs comparable to Why are tropical reefs comparable to rain forests in diversity?rain forests in diversity?– Dissolved nutrients are scarceDissolved nutrients are scarce– Productivity & diversity normally go Productivity & diversity normally go
togethertogether
• Why are tropical reefs disappearing?Why are tropical reefs disappearing?
Increasing threats to coralIncreasing threats to coral
Current bleaching threatsCurrent bleaching threats
What are the challenges?What are the challenges?
• Low nutrients dissolved in waterLow nutrients dissolved in water
• Shallow habitats mean more intense Shallow habitats mean more intense wave actionwave action
• Long-term: sea level changesLong-term: sea level changes
Tropical reefs are geologically Tropical reefs are geologically importantimportant
Reef ecology has long challenged Reef ecology has long challenged biologistsbiologists
Dominant reef-building organismsDominant reef-building organisms
• Small individuals, magnified in effect Small individuals, magnified in effect by large numbersby large numbers
• Phylum CnidariaPhylum Cnidaria– Class AnthozoaClass Anthozoa
•Subclass ZoantheriaSubclass Zoantheria
• Diverse algae, depositing CaCODiverse algae, depositing CaCO33
Cnidaria polyps: radial symmetryCnidaria polyps: radial symmetry
Cnidaria: tentacles for feedingCnidaria: tentacles for feeding
Cnidaria: stinging cells on Cnidaria: stinging cells on tentaclestentacles
Not all corals deposit CaCONot all corals deposit CaCO33
““HermatypicHermatypic” corals create reefs ” corals create reefs in symbiosis with in symbiosis with SymbiodiniumSymbiodinium
Growth forms of colonies reflect Growth forms of colonies reflect tradeoffstradeoffs
• Access to light for symbiotic algaeAccess to light for symbiotic algae– Issues of depth (growth upward)Issues of depth (growth upward)– Issues of competition (shading)Issues of competition (shading)
• Risk of damage from turbulence in Risk of damage from turbulence in shallow seasshallow seas
• Diverse growth forms reflect different Diverse growth forms reflect different balancesbalances
Fast extension: linear growth formFast extension: linear growth form
Extension + more surface area: Extension + more surface area: branchingbranching
Lattice: a subset of “branching” Lattice: a subset of “branching” formform
Plate form: more resistant to Plate form: more resistant to turbulenceturbulence
Massive form: very wave-resistantMassive form: very wave-resistant
Independent algae build reefs: Independent algae build reefs: crustosecrustose
Algae can contribute a large fraction of reef Algae can contribute a large fraction of reef massmass
Independent algae: Green Independent algae: Green ((HalimedaHalimeda))
Reefs: a matrix of solid coral and Reefs: a matrix of solid coral and sandsand
Reef diversity – some examplesReef diversity – some examples
Ecological functional groupsEcological functional groups
A larger scale view: reef building A larger scale view: reef building processprocess
Atoll structureAtoll structure
Habitat diversity within an atollHabitat diversity within an atoll