Reefs

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Reefs
Kinds of buildups Geographic distribution Reef
requirements Community diversity,
environmental mediators, species of great
affect The Sensitive Reef Reefs and Geologic
Time
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Reef requirements 1. Coral reefs are rigid
structures above the sea floor. Keep up with
sea level or drown 2. Biologically mediated 3.
Structure and environemtn
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Reef requirements 1. 3-D topography 2.
Biological Origins and Mediation Created by
organisms Organisms baffle, bind, accrete ?
modify environment 3. Structure and Environment
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Reef requirements 1. 3-D topography 2.
Biologically mediated 3. A complex ecological
and physical structure that exerts control on the
environmet
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Types of Reefs Fringe
Edge of landmass Continents, islands High
energy from waves Small lagoon, if any
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Types of Reefs Barrier
Mature fringe reef without landmass Kept up
with sea level rise ? appears far away from
shore Large, ecologically rich lagoon between
reef and land
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Types of Reefs Atoll
Also formed from fringe reefs Ring structure from
sunken island (subsidence or sea level
rise) Reef with internal lagoon, no land mass
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Types of Reefs Patch
Often in lagoon behind barrier, atoll Low energy
environment Differentiated from surrounding
biota by 3-D topography Biological
mediation Structure and environment
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Types of Reefs Manmade
Accidental (industry, pollutants,
wrecks) Or intentional
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Tropical Reefs around the World
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Biodiversity in Tropical Reefs
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Tropical reef requirements
High light intensity very low turbidity zooxanth
ellae in symbiosis with corals Warm T between
20-30C Constant salinity Nutrients upwelling,
other input BUT nutrient poor waters in
reef Very tightly recycled Constant currents
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Communities 1
Very diverse, highest diversity community in the
world Climax community High degree of niche
specialization Resources very finely partitioned
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Guilds that Mediate Environment
Bafflers corals, sponges
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Guilds that Mediate Environment
Bafflers corals, sponges Binders microbes,
coralline algae, bryozoans
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Guilds that Mediate Environment
Bafflers corals, sponges Binders microbes,
coralline algae, bryozoans Builders corals
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Guilds that Mediate Environment
Bafflers corals, sponges Binders microbes,
coralline algae, bryozoans Builders
corals Eroders parrot fish, echinoids
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Communities 2
Recruitment between reefs and within a
reef Indo-Pacific reefs highest
diversity Oldest reef? Leftover from Tethys?
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The Fragile Reef
Reefs in very fragile balance Algae overgrowth
and echinoids, other grazers Specialists higher
extinction possibility Interactions fairly
tight Species of great effect, keystone
species Physical factors Sea-level rise T
and global warming Nutrient input and algal
blooms Saharan dust and fungus
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Geologic History of Reefs
Earliest buildups Precambrian stromatolites Earl
y Cambrian Archaeocyathid reefs
500MY Devonian Tabulate, rugosa coral
reefs Permian Capitan sponge reef in
TX Cretaceous Various Cenozoic coral reefs