ReefsReefsKinds of buildupsKinds of buildups

Geographic distributionGeographic distribution

Reef requirementsReef requirements

Community: diversity, Community: diversity, environmental mediators, environmental mediators, species of great affectspecies of great affect

The Sensitive ReefThe Sensitive Reef

Reefs and Geologic TimeReefs and Geologic Time

Reef requirements:Reef requirements:1. 1. Coral reefs are rigid structures Coral reefs are rigid structures

above the sea floor. above the sea floor. Keep up with sea level or drownKeep up with sea level or drown

2. Biologically mediated3. Structure and environemtn

Reef requirements:Reef requirements:1. 3-D topography2. Biological Origins and Mediation2. Biological Origins and Mediation

Created by organismsCreated by organismsOrganisms baffle, bind, accrete Organisms baffle, bind, accrete modify modify environmentenvironment

3. Structure and Environment

Reef requirements:Reef requirements:1. 3-D topography2. Biologically mediated3. A complex ecological and physical structure that 3. A complex ecological and physical structure that

exerts control on the environmetexerts control on the environmet

Types of Reefs: FringeTypes of Reefs: Fringe

Edge of landmassEdge of landmassContinents, islandsContinents, islands

High energy from wavesHigh energy from waves

Small lagoon, if anySmall lagoon, if any

Types of Reefs: BarrierTypes of Reefs: Barrier

““Mature” fringe reef without landmassMature” fringe reef without landmass

Kept up with sea level rise Kept up with sea level rise appears far away from shore appears far away from shore

Large, ecologically rich lagoon between reef and landLarge, ecologically rich lagoon between reef and land

Also formed from fringe reefsAlso formed from fringe reefsRing structure from sunken island Ring structure from sunken island

(subsidence or sea level rise)(subsidence or sea level rise)Reef with internal lagoon, no land massReef with internal lagoon, no land mass

Types of Reefs: AtollTypes of Reefs: Atoll

Types of Reefs: PatchTypes of Reefs: Patch

Often in lagoon behind barrier, atollOften in lagoon behind barrier, atollLow energy environmentLow energy environment

Differentiated from surrounding biota by:Differentiated from surrounding biota by:3-D topography3-D topographyBiological mediationBiological mediationStructure and environmentStructure and environment

Types of Reefs: Types of Reefs: ManmadeManmade

Accidental…Accidental…(industry, pollutants, wrecks)(industry, pollutants, wrecks)

……Or intentionalOr intentional

Tropical Reefs around the Tropical Reefs around the WorldWorld

Biodiversity in Tropical Biodiversity in Tropical ReefsReefs

High light intensity: very low turbidityHigh light intensity: very low turbidityzooxanthellae in symbiosis with coralszooxanthellae in symbiosis with corals

Warm T: between 20-30CWarm T: between 20-30C

Constant salinityConstant salinity

Nutrients: upwelling, other inputNutrients: upwelling, other inputBUT: nutrient poor waters in reefBUT: nutrient poor waters in reefVery tightly recycledVery tightly recycled

Constant currentsConstant currents

Tropical reef Tropical reef requirementsrequirements

Communities 1Communities 1

Very diverse, highest diversity community in the worldVery diverse, highest diversity community in the worldClimax communityClimax community

High degree of niche specializationHigh degree of niche specializationResources very finely partitionedResources very finely partitioned

Bafflers: corals, spongesBafflers: corals, sponges

Guilds that Mediate Guilds that Mediate EnvironmentEnvironment

Bafflers: corals, spongesBinders: microbes, coralline algae, bryozoansBinders: microbes, coralline algae, bryozoans

Guilds that Mediate Guilds that Mediate EnvironmentEnvironment

Bafflers: corals, spongesBinders: microbes, coralline algae, bryozoansBuilders: coralsBuilders: corals

Guilds that Mediate Guilds that Mediate EnvironmentEnvironment

Bafflers: corals, spongesBinders: microbes, coralline algae, bryozoansBuilders: coralsEroders: parrot fish, echinoidsEroders: parrot fish, echinoids

Guilds that Mediate Guilds that Mediate EnvironmentEnvironment

Communities 2Communities 2Recruitment between reefs and within a reefRecruitment between reefs and within a reef

Indo-Pacific reefs: highest diversityIndo-Pacific reefs: highest diversity““Oldest” reef?Oldest” reef?Leftover from Tethys?Leftover from Tethys?

The Fragile ReefThe Fragile ReefReefs in very fragile balanceReefs in very fragile balance

Algae overgrowth and echinoids, other grazersAlgae overgrowth and echinoids, other grazersSpecialists: higher extinction possibilitySpecialists: higher extinction possibilityInteractions fairly tightInteractions fairly tightSpecies of great effect, keystone speciesSpecies of great effect, keystone species

Physical factors:Physical factors:Sea-level riseSea-level riseT and global warmingT and global warmingNutrient input and algal bloomsNutrient input and algal bloomsSaharan dust and fungusSaharan dust and fungus

Earliest buildups: Earliest buildups: Precambrian stromatolitesPrecambrian stromatolites

Early Cambrian: Early Cambrian: Archaeocyathid reefs: Archaeocyathid reefs: 500MY500MY

Devonian: Tabulate, Devonian: Tabulate, rugosa coral reefsrugosa coral reefs

Permian: Capitan sponge Permian: Capitan sponge reef in TXreef in TX

Cretaceous: VariousCretaceous: Various

Cenozoic: coral reefsCenozoic: coral reefs

Geologic History of Geologic History of ReefsReefs