Coral Reefs

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Coral Reef Biology

Kingdom AnimaliaPhylum Cnideria

Class Hydrozoa- hydroidsClass Scyphozoa- jelliesClass Cubozoa- box jelliesClass Anthozoa- corals and anemones

The Cnidarian Life Cycle

The Hydrozoan Life CycleThe Hydrozoan Life Cycle

Class HydrozoaHydrozoan ColonyClass Hydrozoa

Hydrozoan Colony

Hydrozoan Colonies“Stinging Limu”

Hydrozoan Colonies“Stinging Limu”

Fire CoralFire Coral

By-the-Wind-SailorA Floating Colony of Polyps

By-the-Wind-SailorA Floating Colony of Polyps

Coloniality Man-of-War

Phylum Cnidaria Man-of-War

Phylum Cnidaria

Close Up of a Portuguese Man-Of-War

Close Up of a Portuguese Man-Of-War

Class Scyphozoa

Class CubozoaBox Jellies

& Sea Wasps

Class CubozoaBox Jellies

& Sea Wasps

Class Anthozoa

Sea Anemones &

Corals: true stony corals and octocorals

Sea AnemonesSea Anemones

Sea Anemone AnatomySea Anemone Anatomy

Hermatypic corals:• possess zooxanthellae• are reef builders

Light: Clear water Warm temperature: 18-32oCLow nutrientsLow productivity in water

Ahermatypic corals:• no zooxanthellae• rely on tentacular feeding• can live in aphotic zone

Distribution of Coral Reef Communities

Cauliflower coral(Pocillopora meandrina)

6 m

0 m

25 m

13 m

Lobe coral(Porites lobata)

Finger coral(Porites compressa)

Plate coral(Porites rus)

High light levelsModerate wave energy

Moderate light levelsOccasional storm wave energy

Low light levelsLow wave energy

Very low light, Primarily downwelling No wave energy

“True” Stony Corals“True” Stony Corals

“True” Stony CoralsHermatypic- reef building, zooxanthellae

Common species:• Acroporidae- table• Acroporidea- rice • Agariciidae- flat lobe, corregated• Faviidae- crust, ocellated• Fungiidae- humpback, mushroom• Pocilloporidae- lace, antler, cauliflower• Poritidae- finger, lobe, plate

Family PocilloporidaeLace coral, antler coral, and cauliflower coral

Pocillopora damicornis

lace

Pocillopora eydouxi

antler

Pocillopora meaandrina

cauliflower

Family Acroporidae

Table coral, rice coral and spreading coral

Montipora flabellata Montipora patula

rice coral

Montipora capitata Acropora cytheria

table

Family Poritidae

Finger coral, lobe coral, Evermann’s coral, plate and pillar coral

Porites evermanni

Porites rus Porites compressa

Porites lobata

Family Agariciidae

flat lobe coral, corrugated coral

Pavona duerdeni

Pavona varians

Flat lobe

corrugated

Family Fungiidae

Humpback coral, mushroom coral

Fungia scutaria

mushroom

Family Faviidaecrust coral, ocellated coral

Cyphastrae ocellina

Leptastrea bottae

Leptastrea purpurea

A Solitary Coral PolypA Solitary Coral Polyp

Colonial Coral PolypsColonial Coral Polyps

Zooxanthellae in Gastrodermal Cells of Corals

Zooxanthellae:Symbiodinium microadriacticum

• Octocorals, wire corals, black corals, sea pens

• Both hard and soft forms exist• non reef-building• no photosynthesis

Ahermatypic Corals

Ahermatypic CoralsAhermatypic Corals

Heterotrophic NutritionHeterotrophic Nutrition

General feeding modes:1. predaceous carnivores capturing live

prey2. detritus feeding3. absorption of dissolved organic

matter from surrounding water

Nematocyst Discharge

Photosynthesis

6H2O + 6CO2 + light C6H12O6 + 6O26H2O + 6CO2 + light C6H12O6 + 6O2

Autotrophic NutritionAutotrophic Nutrition

Zooxanthellae in Coral Polyp

Benefits to the Algal Symbiont

• Zooxanthellae gets a place to live

• Receive chemical wastes from animal metabolism (CO2 & NH3).

• Surrounding animal tissues can concentration substantial amounts of ultraviolet light absorbing compounds.

Benefits to the Coral Host• Higher rates of calcification (skeleton

deposition).• Receive DOM & O2 • Removal of chemical wastes from

animal metabolism (CO2 & NH3).• Receive chemicals that absorb

damaging ultraviolet light (Micosporine-like amino acids (MAAs)).

Asexual Reproduction

• budding and fissionbudding and fission• accidental fragmentationaccidental fragmentation• nonaccidental fragmentationnonaccidental fragmentation• partial colony mortalitypartial colony mortality• polyp bail-outpolyp bail-out

Budding

Polyp within calyx

FissionPolyp within calyx

AccidentalFragmentation Wave Damage Wave Damage

Nonaccidental Fragmentation

Radial Division in Radial Division in Cycloseris fragilisCycloseris fragilis

Nonaccidental Fragmentation

Transverse Division in Transverse Division in Fungia scutariaFungia scutaria

anthocaulusanthocaulus

anthocyathusanthocyathus

Nonaccidental Fragmentation

Transverse Division in Transverse Division in Fungia scutariaFungia scutaria

stalk regenerates new disk

Partial Colony MortalityThe Phoenix EffectThe Phoenix Effect

in in Porites compressaPorites compressa

P. JokielP. JokielP. JokielP. Jokiel Cut surface of a broken finger showing living tissue beneath the surface of the skeletonNormal colony next to

a colony exposed to freshwater

Polyp Bail-Out

D. GulkoD. Gulko

zygote

Sexual ReproductionSexual Reproduction

planula larvae

egg

sperm

Planula Larvae

Sexual Reproduction

• Hermaphroditic vs gonochoric

• Broadcast spawning vs brooding

Sexuality

Acropora sp., a hermaphoditic coralAcropora sp., a hermaphoditic coral

Fungia scutaria, a gonochoric coralFungia scutaria, a gonochoric coral

eggseggs

sperm packetsperm packet

egg cloudegg cloud

Hermaphroditism: sexes in same individualGonochoric: separate sexes

Brooding Versus Broadcast Spawning

BroodingBroodingeggs develop to planula stage in gastrovascular eggs develop to planula stage in gastrovascular cavity of parent polypcavity of parent polyp

Broadcast SpawningBroadcast Spawningeggs and sperm are shed into the water column eggs and sperm are shed into the water column where fertilization and development occurswhere fertilization and development occurs

BroodingBroodingeggs develop to planula stage in gastrovascular eggs develop to planula stage in gastrovascular cavity of parent polypcavity of parent polyp

Broadcast SpawningBroadcast Spawningeggs and sperm are shed into the water column eggs and sperm are shed into the water column where fertilization and development occurswhere fertilization and development occurs

broadcast spawnerbroadcast spawnerPocillopora damicornis, a brooderPocillopora damicornis, a brooder

planula in polypplanula in polyp

released gametesreleased gametesD. GulkoD. Gulko

Environmental Factors Affecting Corals

Environmental Factors Affecting Corals

• Water Motion

• Depth: photic vs aphotic zone & water motion

• Sedimentation

• Salinity: 32-35o/oo

• Temperature: 18-32 oC

• Tidal fluctuations

• Nutrients: Eutrophic vs oligotrophic

• Water Motion

• Depth: photic vs aphotic zone & water motion

• Sedimentation

• Salinity: 32-35o/oo

• Temperature: 18-32 oC

• Tidal fluctuations

• Nutrients: Eutrophic vs oligotrophic

Hanauma BayMamala Bay

Kaneohe Bay

Sunset Beach

Coral reefs presently exist on every island and shallow bank in the Hawaiian chain

Fringing Reef- 100-1000 years to form youngest is on west coast of Hawaii

Barrier Reef- 2.5 ma to form Kaneohe & Moanalu Bay

Atoll- 10 ma to formfirst atoll French Frigate Shoals, dated 11.7 mya

Coral reef growth limited by:• wave exposure• sea level

Sheltered sites:Hanauma Bay and Kaneohe BayReef accretion ~ 2mm/yr

Wave exposed sites:Mamala Bay and Sunset BeachReef accretion ~ 0 mm/yr shallow (1m) and deep (12m)

Environmental Factors Affecting Corals

Environmental Factors Affecting Corals

• Water Motion

• Depth: photic vs aphotic zone & water motion

• Sedimentation

• Salinity: 32-35o/oo

• Temperature: 18-32 oC

• Tidal fluctuations

• Nutrients: Eutrophic vs oligotrophic

• Water Motion

• Depth: photic vs aphotic zone & water motion

• Sedimentation

• Salinity: 32-35o/oo

• Temperature: 18-32 oC

• Tidal fluctuations

• Nutrients: Eutrophic vs oligotrophic

Oligotrophic vs Eutrophic

                                       

Reef Critters

coralivore

Coral Reefs:Threats

Starfish: “crown of thorns” (why?)

Coral is a source of building materials

Pollution: particles in the water

Human impacts on coral includes:

• Aquarium/Souvenir Trade• Overfishing• Pollution• Dredging• Coastal Development• Tourism• Global Climate Change• Ozone Depletion

Coral Reefs: Human Impact

Worldwide disappearance

Fishing with explosives

Waste oil dumping

Sediments

Philippines: 75% of the reefs damaged

Dynamiting Reef

Destructive Resource Extraction Practices

Destructive Resource Extraction Practices

Toxic Chemical SpillsToxic Chemical Spills

Sediment Plume Entering the OceanSediment Plume Entering the Ocean

Corals Smothered in SedimentCorals Smothered in Sediment

DredgingDredging

Coastal DevelopmentCoastal Development

Anchor DamageAnchor Damage

Diver DamageDiver Damage

Ecotourism

Pennekamp Reef, Key Largo, FL

Net DamageNet Damage

Net Entanglement

                  

 

                        

                                                                        

Overfishing and Bycatch

Ornamental Trade:

Fan worm

Threadfin Butterfly fish

Introduced SpeciesIntroduced SpeciesAcanthophora, Eucheuma, & Gracillaria

Feeding Fish

Hanauma BayHanauma Bay

Kaneohe Bay and Bubble algae

Nutrients and Algae Growth

Dictyosphaeria cavernosa

BleachingBleaching

Global Bleaching (2002)Global Bleaching (2002)

none

low

moderate

severe

severity unknown

Acid Rain in Marine EnvironmentAcid Rain in Marine Environment

• reduces ability of marine organisms to utilize calcium carbonate

• Coral calcification rate reduced 15-20%

• Skeletal density decreased, branches thinner

Sea Level RiseSea Level Rise