Cnidaria phylum

Cnidaria is a phylum containing over 9,000 species found only in aquatic and mostly marine environments. All cnidarians have radial symmetrical. There are two major body forms among the Cnidaria - the polyp and the medusa. Sea anemones and corals have the polyp form, while jellyfish are typical medusae.

2. Phylum Cnidaria
Allaquatic,mostlymarineandsomefreshwater.
Acoelomate
Exoskeletonchitinousorcalcareous.
Bodywalldiploblasticwithtwocellularlayers-outerepidermisandinner
gastrodermiswhichformsagastrovascularcavitywithagelatinousacellular
mesogleainbetween.Inadvancetypes,itistriploblastic.
gastrovascularcavityorcoelenteronisasingleinternalcavityintowhichmouth
opensanditislinedwithgastrodermis
Twobasicformsofindividual-
Polyp:Cylindricalformwhichattachbasestosubstratum
Medusa:Flattened,mouthdownversionofthepolyp.Movesfreely
Mouthofpolypsandbellmarginofmedusaeoftenencircledbyshortandslender
tentacles.
Norespiratory,circulatoryandexcretorysystem
Anusisabsent
Peculiarstingingcellorganellesornematocystswithoneorbothbodylayershelpfor
adhesion,foodcaptureandoffenceanddefense.

4. Polymorphism
Occurrenceinthesamespeciesofmorethanonetypeofindividuals,whichdifferinformandfunction,isknownas
polymorphism(Gr.,polys=many+morphe=form).
Itisanimportantfeatureofsingleorcolonialhydrozoan-whichincludedinhydrozoaclass.
Twobasicformsofindividual-
Polyps:
-Ithasatubularbody
-Mouthissurroundedbytentaclesatoneend
-Otherendisusuallyattachedbyapedaldisctothesubstratum.
-Sessile
-Partofthebenthiccommunity
 Medusae:
-Bowlorumbrella-shapedbodywhichiscalledbellwithmarginaltentacles
-Mouthcentrallylocatedonaprojectionofthelowerconcavesurface
-Free-floatingormotile,movebyweakcontractionsofbody
-Partoftheplankton
 Polymorphismensuresanefficientdivisionoflabourbetweentheseveralindividuals.
 Differentfunctionsareassignedtodifferentindividuals,ratherthantopartsororgansofoneindividual
 Polypsareconcernedwithfeeding,protectionandasexualreproduction
 Medusaeareconcernedwithsexualreproduction

5. Patterns of polymorphism
Dimorphic:
Simplestandcommonestpatternofpolymorphism
Thecolonieswhichbearonlytwotypesofindividualsarecalleddimorphicand
thephenomenonistermeddimorphism
ItisshowninmanyhydrozoancolonieslikeObelia,Tubularia,Campanularia
etc.
Theyhaveonlytwotypesofindividuals-Gastrozooidsorhydranthsand
gonozooidsorblastostyles
Gastrozooidsareconcernedwithfeedingandgonozooidsconcernedabout
sexualreproduction.
Trimorphic:
SomecoloniessuchasPlumulariawhichpossessthreetypesofindividuals
arecalledtrimorphic
Thethreetypesofindividuals-Gastrozooids,gonozooidsanddactylozooids.
Dactylozooidsarefunctionallynon-feedinganddefensivepolypsbearing
batteriesofnematocysts

6. Polymorphic:
Coelenterateshavingmorethanthreetypesofindividualsare
calledpolymorphic.
ThecolonyofHydractiniahasfivetypesofpolypswhichperforma
specializedfunction.
Thefivetypesofindividuals-(i)Gastrozooidsforfeeding,(ii)spiral
dactylozooidsforprotection,(iii)longsensorytentaculozooidswith
sensorycells,(iv)skeletozooidsasspinyprojectionsofchitinand(v)
gonozooidsorreproductiveindividuals,bearingmaleorfemale
gonophoresormedusaeforsexualreproduction.

7. Physical structure
Aurelia : A Jelly-fish:
Shape: Umbrella-shaped body
-four red or purple horseshoe-shaped gonadson its upper surface of body
-Four long and narrow oral lobes hanging downwards from lower surface
-Its circular body presents a convex aboralor exumbrellarsurface and a concave oral or
subumbrellarsurface.
1)Manubrium, mouth and oral arms
2)Nematocysts
3)Subgenitalpits
4)Gonads

8. 5)Lappetsandrhopalium:
-Thecircularmarginofumbrellaorbellisbrokeninto8lobesornotches
-Ineachnotch,therearetwodelicateleaf-likeprocesses,calledthemarginal
lappets.
-Asmallsensoryorganliesbetweenlappets,calledtherhopaliumortentaculocyst
6)Marginaltentacles:Itbearsbatteriesofstingingcellsornematocysts.
7)Velarium

9. Velarium

10. Nutrition
Cnidariansarecarnivores
Theyeatsmallaquaticanimalssuchasinsectlarvae,crustaceans(Cyclops,
Daphniaetc.),annelidworms,youngfishes,tadpoles,nematodesetc.
Thegastrovascularcavityexistsas1openingforfoodintakeandtheelimination
ofwaste
Thereisnosystemofinternaltransport,gasexchangeorexcretion;allthese
processestakeplaceviadiffusion

11. Stinging Organelles
Cnidariansarepredatorswhichhavetentacles
possessingbatteriesofspecialcellscalled
Cnidocytesornettlecells.
Preycaptureisenhancedbyuseofspecialized
stingingcellscalledcnidocyteslocatedinthe
outerepidermis.
Eachcnidocyteisarmedwithastinging
structurecalledanematocysts.
Theundischargednematocystiscomposedof
alongcoiledthread
Whentriggeredtorelease,eitherbytouchor
chemosensation,thenematocystisreleased
fromthecnidocyteandthecoiledthreadis
discharged.
Whentriggered,thesecellsshootouta
dischargethreadwhichcanentangleand/or
poisonit'sintendedprey

14. Reproduction
Budding Regeneration

15. Sexual Reproduction

17. •Gametesdevelopingastrodermisofgastricpouches;eggsandspermareshed
throughmouth
•Fertilizedeggsdevelopintoaplanulalarva;settlesonsubstrateanddevelopsinto
apolyp-scyphistoma
•Scyphistomaproducesaseriesofpolypsbybudding-strobila
•Thepolypsundergodifferentiationandarereleasedfromthestrobilaasfree
swimmingephyra
•Ephyramaturesintoanadultjellyfish

18. Class 1. Hydrozoa
(Gr., hydra, water+ zoon, animal)
•Mostvariedandderivedofthecnidariangroups
•Freshwaterormarinee.g.Hydrasp.
•Onlypolypsorbothasexualpolypsandsexualmedusae
present
•Medusawithtruevelum
•Mesogleanoncellular
•Sexcellssheddirectlyonoutside
•Mosthavetypicaldimorphiclifecycle
•Examplesofpolyp-onlyformse.g.Hydra
•Examplesofmedusa-onlyformse.g.Polycolpa

20. Class 2. Scyphozoa
•Typically thought of as jellyfish
•Exclusively marine
•Most have typical dimorphic life cycle
•Medusa stage is dominant. Polyp stage reduced or
absent
•Majority of life cycle spent in medusa form
•Medusa without distinct velum
•Mesoglea extensive, gelatinous with fibre and cells
•Sex cells released in digestive cavity
e.g. Aurelia

21. Aurelia aurita (Moon jelly)

22. Lion’s Mane Jelly (Cyanea capillata)

23. Class 3. Anthozoa
Exclusivelymarine
Allpolyps,nomedusae.
Gastrovascularcavitysubdividedby8ormoreseptaormesenteries
Mesenterieswithnematocystsandgastrodermalglands
Mesogleastoutandcellular
Includesseaanemonesandcorals
Coralsbuildcalciumshellstoprotectthemselves
Havesymbioticrelationshipwithalgae.
Canbuildextensivemasseswhichcanformlandmasses
e.g.Metridium

24. Class Anthozoa –Typical Polyp Form

27. Anemone with Anemone Fish

28. Coral Reefs
Coral Polyps

29. Coral
•Coral is actually an animal.
Coralanimalsorcoralsaremarine,mostlycolonial,polypoid
cnidarians
MostofthecoralsbelongtotheclassAnthozoaandafewtothe
classHydrozoaofphylumcnidaria.
Coralsaresessileanimalsandarethebuildersofthereef!
Theyaredifferentfrommostothercnidariansbecausetheyhaveno
medusastageintheirlifecycle.
Thebodyunitoftheanimalisapolyp.Asinglecoralanimalis
calledacoralpolyp.
Theytypicallyliveinasecretedskeletonoftheirown.Their
calcareousorhornyskeletonisalsocommonlyknownascoral

30. Structure of coral polyp
Atypicalcoralpolypisasmallorganismabout10mmlongand1to3mmin
diameter.
Solitarycoralpolypismuchlarger–upto25cmindiameter.
Abasaldiscisabsent
Basalregionofpolypissurroundedbyacalcareousexoskeleton.
Overmanygenerations,thecolonythuscreatesalargeskeletonthatis
characteristicofthespecies.
Centralmouthopeningororaldiscbearsnumeroustentaclesinseveral
rowsaroundanelongated,ovalorcircularmouth.
Pharynxisshort.
Mesenteriesarerestrictedtotheupperpartofthecoelenteron.
Mesenterialfilamentscontainonlyoneglandularlobebearingnematocysts
Livingpolypsarefoundonlyonsurfacelayersofcoralmasses

32. Structure of coral skeleton
Eachpolyphasacup-likeshape
Thereisnoskeletoninsidethepolypitself.Instead,thepolypssitontopofan
externalskeletonthatismadefromthepolyp'ssecretions.
Theskeletonsofcoralsaresecretedbythelowerportionofthepolyp.
Thecupshapedcalcareousexoskeletonofcoralisknownascorallitewhich
isseretedbytheepidermisofanindividualstonycoralpolyp
composedofaragonite,acrystallineformofcalciumcarbonate
Incolonialcoral,corallitesofindividualpolypsfusetogethertoformaskeletal
mass,calledcorallum
concavedepressionthathousesthepolyporTheinnersurfaceofthe
coralliteisknownasthecalyx.

33. Thewallssurroundingthecorallitearethetheca
Theskeletalplatesthatradiateintothecalyxfromthewall
calledseptum(sometimescalledscleroseptum)andthese
platesextendoutsidethecorallitewallcalledcostae
Innerendsofscleroseptumarefusedtoformanirregular
centralskeletalmassorcolumella.
Incolonialcoral,theskeletalmaterialbetweenwallsof
adjacentcorallitesiscalledcoenosteumandthelayerof
livingtissuethatcoversthecoenosteumorskeletonofthe
coraliscalledcoenosarc

35. Aslongasthecolonyisalive,apolypwillliftoffitsbaseand
secreteanewfloortoitscupbydepositingcalciumcarbonate,
forminganewbasalplateabovetheoldone.
Overtime,aseriesoffloorsbuildsupbelowthelivingpolyps,
resultinginathickeningandlateralexpansionofthecoral.
Whenpolypsarephysicallystressed,theycontractintothecalyx
sothatvirtuallynopartisexposedabovetheskeletalplatform.
Incolonialspecies,whenthecoralliteseachhaveasurrounding
wall,thecolonyissaidtobeplocoid.Whenthewallsaretalland
tubular,thecolonyisphaceloid,andwhenseveralpolypssharea
commonwall,thecolonyiscerioid.Sometimesthepolypsarein
valleysonthesurfaceofsolidcorals,theyarethenknownas
meandroid

36. Polyps Outside!Polyps Inside
Tiny, little animals!

38. Feeding
Coralsfeedonavarietyofsmallorganisms,frommicroscopiczooplanktontosmallfishbyusing
stingingcellsoftentacles
Thepolyp'stentaclescatchorimmobilizeorkillpreyusingtheirnematocysts.
Theycanscavengedriftingorganicmoleculesanddissolvedorganicmolecules
Mostcoralsonlyextendtheirpolypsandtentaclesatnightwhenzooplanktonismostabundant,
butsomecorals(especiallysoftcorals)keeptheirpolypsopenthroughouttheday.
mostcoralsobtainthemajorityoftheirenergyandnutrientsfromthesymbioticrelationshipwith
photosyntheticunicellulardinoflagellatesthatlivewithintheirtissues.Thesearecommonlyknown
aszooxanthellaeandthecoralsthatcontainthemarezooxanthellatecorals.e.g.Symbiodinium
Thealgaeproducesenergy-richsugarsandfatsviaphotosynthesisandprovidesenergytothe
corals.Thishelpsthecoralgrowandproduceitsskeletonfasterthanacoralwithoutthe
zooxanthellae.
Inreturn,thealgaehaveasafeplacetolivewithinthecoraltissueandthealgaeusesthecoral's
carbondioxideandwastenutrientsforgrowth.
Suchcoralsrequiresunlightandgrowinclear,shallowwater,typicallyatdepthsshallowerthan
60metres(200ft).
Thezooxanthellaealsogivesthecoralitscolor.
Othercoralsdonotrelyonzooxanthellaeandcanliveinmuchdeeperwater,survivingasdeep
as3,000metres(9,800ft).e.g.Lophelia

40. Class Anthozoa–Hard Coral
•Theyarecalled“hard"or“stony”becausetheyhaverigid
calciumcarbonateskeletons
•TheyarealsomembersoftheSubclassHexacoralliaand
orderScleractinia
•Thepolypsproduceaskeletoncomposedofcalcium
carbonatetostrengthenandprotecttheorganismwhich
aredepositedbythepolypsandbythecoenosarc,the
livingtissuethatconnectsthem.
•composedofaragonite,acrystallineformofcalcium
carbonate
•stonycoralsrelyingontheirhardskeletonandcnidocytes
fordefenceagainstpredators
•Thepolypsofstonycoralshavesix-foldsymmetry
•Thetentaclesarecylindricalandtapertoapoint
e.g.:Pocilloporadamicornis,Pocilloporaelegans,Faviabestae

43. Class Anthozoa–soft corals
•Theyarecalled"soft"becausetheydo
notconsistofrigidcalciumcarbonate
skeletons
•TheyarealsomembersoftheSubclass
OctocoralliaandorderAlcyonacea,
knownastheOctocorals.
•thereisnostonyskeletonbutthe
tissuesareoftentoughenedbythe
presenceoftinyskeletalelements
knownassclerites,whicharemade
fromcalciumcarbonate.
•Composedeitherofafibrousprotein
calledgorgoninorofacalcifiedmaterial
•Thepolypsofsoftcoralshaveeight-fold
symmetryi.e.polypswitheighttentacles
andeightmesentaries.
•Thepolypsofsoftcoralshaveeight
tentacles

44. Formcomplextube-likeskeletalstructures
softcoralsgenerallyrelyingonchemicaldefencesintheformoftoxic
substancespresentinthetissuesknownasterpenoids
Thepolyptentaclesofsoftcoralshavenumerousside-branches,or
pinnules,whichgivethepolypsafeatherylook
mostsoftcoralsthriveinnutrient-richwaterswithlessintenselight
e.g.Dendronephthyaklunzingeri,Alcyoniumsp.,Clavulariasp.,Lemnalia
sp.

46. Stonycoralsfallintotwomainecologicalgroups
Reef-formingorhermatypiccorals,whichmostlycontainzooxanthellae;
Non-reef-formingorahermatypiccorals,whichmostlydonotcontainzooxanthellae
Hermatypiccoralsaremostlycolonialcoralswhichtendtoliveinclear,oligotrophic,shallow
tropicalwaters;
formlargecolonies
theyaretheworld'sprimaryreef-builders.
Ahermatypiccoralsareeithercolonialorsolitaryandarefoundinallregionsoftheoceanand
donotbuildreefs.
aresolitaryorformsmallcolonies
Someliveintropicalwatersbutsomeinhabittemperateseas,polarwaters,orliveatgreat
depths,fromthephoticzonedowntoabout6,000m(20,000ft)
Theythriveatmuchcoldertemperaturesandcanliveintotaldarkness,derivingtheirenergy
fromthecaptureofplanktonandsuspendedorganicparticles.
Thegrowthratesofmostspeciesofnon-zooxanthellatecoralsaresignificantlyslowerthan
ooxanthellatecorals
thetypicalstructureforthesecoralsislesscalcifiedandmoresusceptibletomechanical
damagethanthatofzooxanthellatecorals
Examplesofahermatypiccoralsaresoftcorals,blackcorals,gorgonians,preciouscorals

47. Soft Corals –Class Anthozoa

48. Reproduction -Sexual
•Coralscanbebothgonochoristic(unisexual)andhermaphroditic
•Spawningtechniques
BroadcastSpawners
Brooders
BroadcastSpawners
About75%ofallcorals"broadcastspawn"byreleasinggametes—eggsand
sperm—intothewatertospreadoffspring.
Thegametesfuseduringfertilizationtoformamicroscopiclarvacalledaplanula,
typicallypinkandellipticalinshape.
Planulalarvaedisperseandsettleonhardsubstrateinclearshallowwaterand
beginproducingatinycalciumskeleton.
Atypicalcoralcolonyformsseveralthousandlarvaeperyeartoovercomethe
oddsagainstformationofanewcolony.
Generallyallcoralsspawnonthesamenight.
Coralsrelyonenvironmentalcuessuchastemperaturechange,lunarcycle,day
length,andpossiblychemicalsignalingtodeterminethepropertimetorelease
gametesintothewater.

49. Brooders:
Broodingspeciesaremostoftenahermatypiccorals(notreef-building)
inareasofhighcurrentorwaveaction.
Broodersreleaseonlysperm,whichisnegativelybuoyant,sinkingon
tothewaitingeggcarrierswhoharborunfertilizedeggsforweeks.
Afterfertilization,thecoralsreleaseplanulathatarereadytosettle

50. Reproduction -Asexual
•Twomainways:
–Budding(Extratentacularbudding)
•Thepolypsbudoffafromthesidecreatinganewpolyp
–Fission(Intratentacularbudding)
•Polypssplitintohalfthroughthetentaclescreatingthenewpolyp
•Newcoloniescanalsoformbyfragmentation
–Brokenpiecesofacolonyfalloffandreattachthemselvestothesubstrate
•AdvantageisthatthenewcolonyismorelikelytosucceedthanPlanularLarvae
•Disadvantageisthatthenewcolonyisclonedandthereforesusceptibletothe
samediseasesastheparentcolony

51. Coral reef
Coral colonies grow continuously in size by
budding of polyps and often form extensive
masses known as coral reefs
Principle builders of coral reefs are stony
corals and coralline algae and Foraminiferan
protozoa also take part in the formation.
Coral reef are also called as ‘Rainforests of the
Sea’

52. Zooxanthellae
Coral polyp
Coral colony
Corals
Coral
Reef
Zooxanthellae
Coral polyp
Coral colony
Corals
Coral
Reef

53. Kinds of coral reefs
•Fringingreefs:
Thiscoralreefsarelyingclosetotheshoresofsomevolcanicisland
orpartofsomecontinentaretermedfringingreefs
Ashallowwaterchannel-50to100m
Betweenthereefedgeandshore
Composedofcoralsand,mud,deadandlivingcoralcoloniesand
otheranimals
•Barrierreefs:
Theyarelocatedsomedistanceawayfromtheshore
Lagoonseparatethereeffromtheisland
Lagoonis10to50fathomsdeepandSuitablefornavigation
•Atoll:
Alsotermedascoralislandorlagoonisland
Ring-likeorhorse-shoeshapedreefsthatsurroundsalaggon
Maybecompleteorbrokenbyanumberofchannelsofwhichonlya
fewarenavigable

55. Why are coral reefs important?
•Habitat:They are home to
33% of all known fish species.
•Nursery: And a nursery ground
for over 25% of all marine
species.
Photo by J. RandallPhoto by Dee Wescott
Photo by MacGillivray Freeman Films
•Habitat:They are home to
33% of all known fish species.
•Nursery: And a nursery ground
for over 25% of all marine
species.

56. Reefsarehome toalargevarietyoforganisms,including
fish,seabirds,sponges,cnidarians(whichincludessometypesofcorals
andjellyfish),worms,crustaceans(includingshrimp,cleanershrimp,
spinylobsters and crabs), mollusks (including
cephalopods), echinoderms(includingstarfish,seaurchinsandsea
cucumbers),seasquirts,seaturtlesandseasnakes.

57. Fish–Some fish feed on small animals living near the coral or on the
coral itself; other fish, including some sharkscruise the perimeter of the
coral reef.
Algae–Though a vital part of reef life, overfishing and excess
nutrients from onshore can lead to algae encroachment, where
algae can outcompete and kill the coral
Organisms that are part of Reefs include:
Life on a Reef
1
2

58. Seabirds–Coral Reef systems provide habitats for seabird species, many
of which are endangered. The short-tailed albatross has only 2200
surviving species
Cnidarians–organisms like jellyfishwith specialized cells called
cnidocytes. Cnidocytes are used used mainly for capturing prey which
ranges from the size of plankton to animals larger than themselves.
:
Life on a Reef, Continued
Item
3
Item
4
5
Other inhabitants–Sea snakes and land based reptiles
(crocodiles, lizards) feed on fish and their eggs.

59. Why are coral reefs important?
•Food: they are a food source
for millions of people.
•Tourism: coral reefs attract
tourists from all over the
world.
•Income:they provide millions of
dollars of income annually for
people living by coral reefs.
•Medical Research: coral reefs have
the potential to be used as medical
cures to treat cancer, heart disease,
HIV and arthritis among others.
•Protection: they protect 20% of
the world’s coast from wave erosion.
•Food: they are a food source
for millions of people.
•Tourism: coral reefs attract
tourists from all over the
world.

60. Why do we have to care about Corals?
•Ecological value: corals sustain rich marine biodiversity.
(ex. Shelter for some animals, food for other animals)
350 million coastal people rely directly on coral reefs for
their food and survival.
•Economical value: tourism, fishery industry
(ex. Divers, tourists, and food supply
Over 20 million scuba divers visit coral reefs each year.
•Environmental value: they provide protection for us.
(ex. Breaking storm wave, tsunami, typhoon, erosion
and flooding)

61. Environmental requirements
•Physical environment
–Temperature of 25-31
o
C
–Salinity of 34-37 ppt
–Sunlight
–High Water Transparency
–Good water circulation
•Biological environment
–Oligotrophic, highly stratified water column

62. Threats to coral reef systems
•There are two types of threats to coral
reefs, anthropogenic and natural
•Overpopulation
•Unsustainable fisheries
•Destructive and non-sustainable fishery
practices
•Coastal development
•Global climate change
•Coral bleaching –socio economic
impacts, reef based tourism and
fisheries
•Coral mining –construction, lime
industry, ornamental purposes
•Pollution –agriculture, coastal
development
•Sedimentation -deforestation

63. Threats from Nature
•Unusually strong waves such as those from a
hurricane
•Water temperature changes
•Dramatic changes in saltiness of water
•Predators, such as snails and crown of thorns
starfish
•Overgrowth of algae

64. Coral-eating Snails

65. Crown of Thorns
•Thecrown-of-thornsseastar,Acanthasterplanci,isa
large,multiple-armedstarfish(orseastar)thatusually
preysuponhard,orstony,coralpolyps(Scleractinia).
•Thecrown-of-thornsseastarreceivesitsnamefrom
venomousthorn-likespinesthatcoveritsuppersurface,
resemblingtheBiblicalcrownofthorns.Itisoneofthe
largestseastarsintheworld.
•Eatscoral
•Aggregationscanremove95%ofcoralcover
•Mayresultincollapseofremainingskeleton
•Pheromonecontrolledaggregatedspawning
•Recoverytakesatleast12years

66. Crown of Thorns Starfish

67. What are the man-made threats to
coral reefs?
An example of coral bleaching.
•Global warmingleading
to coral bleaching.
•Runoff of chemicals and
nutrients from landla
•Rubbishincluding marine
debris
•Overfishing
•Physical damage from
tourists and fishermen
•Pollution from untreated
sewage and oil.
•Sedimentation
•Ocean acidification

68. Threats from Humans
•Pollution
–Sedimentsblock light from zooxanthellae
–Chemicalseither poison corals or allow too much
algae to grow
•Power plants
–Filter water and kill fish and plankton
–Releasing hot water kills organisms

69. Pollution

70. Power Plants

71. More Threats from Humans
•Deforestation
–Causes erosion which clouds the water
–Burning of trees could be a factor in climate change
•Destructive fishing
–Blasting with dynamite
–Cyanide poison
–Boats running aground, anchors
–Overfishing

72. •Themainthreattocoralreefsfromclimatewarmingiscoralbleaching,
howeverthereareotherthreatsfromclimatewarmingsuchasocean
acidificationandrisingsealevels.
•Pollutionfromlandactivitiessuchasfarmingandlanddevelopmentincreases
thenutrientconcentrationinthewater.Elevatednutrientconcentrations
resultinarangeofimpactsoncoralcommunities,andunderextreme
situationscanresultincoralreefcommunitycollapse.Elevatednutrient
concentrationsaffectcoralsbypromotingphytoplanktongrowth,whichinturn
supportsincreasednumbersoffilterfeedingorganismssuchastubeworms,
spongesandbivalvesthatcompetewithcoralforspace.Macroalgalblooms
canalsoresultunderenhancednutrientregimesandmacroalgaemay
overgrowcoralstructures,out-competingcoralforspaceandshadingcoral
coloniestocriticallevels.
•Sedimentationcausesproblemsforthecoralbydecreasingavailablelightand
smotheringthecoralandothersurfaces.
•Overfishingremoveskeystonespeciesfromthecoralreefecosystemupsetting
thedelicatebalance.
•Unsustainabletourismleadstoincreasingpollutionanddamagetothecoral.

73. 1) Use of gears and mesh sizes not sanctioned by
government
2) Use of gears and mesh sizes not sanctioned
within the fisherfolkcommunity…
3) Use of gears that destroy the resource base
4) Use of gears such as dynamite or sodium cyanide
that do all of the above and even endanger the
fisherfolksthemselves”

74. Climate change
•Potential impacts on coral communities
–Changes in water temperature
–Increases in CO
2concentration
–Changes in solar irradiation (if cloud cover
changes)
–Sea level rises leading to drowning of reefs
–Changes in surface run-off (sedimentation)
–Changes in land-use patterns leading to increased
reef exploitation

75. What is Coral Bleaching?
•CoralBleaching=Coralswhich
losttheirsymbioticalgaeappear
whitish.
•Coralsarecompelledtoexpelthe
algaebecauseofitstoxinwhen
theyareunderstressfulcondition.
•Unusualhighwatertemperature
isthoughtasthemaincauseof
themassbleachingeventin
1997~98.
•Somespeciescansurvive
bleachingbuttheaftereffect
includesslowergrowth,fragile
bodyandhigherriskofdisease.

76. Coral Bleaching
•First described in 1984
•Multiple re-occurrences at same sites
•New sites impacted during 1990s
•Many known triggers
–Temperature (especially increases)
–Solar radiation (especially UV)
–Combination of UV and temperature
–Reduced salinity
–Infections

77. Effects of bleaching
•Loss of symbiontic algae (Zooxanthellae) algae by:
–Degradation In situ
–Loss of algae by exocytosis
–Expulsion of intact endodermal cells containing algae
•Resulting impacts
–Vary between species, and even parts of the same colony
–Loss of sensitive species (especially Acroporaspp.)
–Recovery slow and highly variable between sites

78. The Problems
•A large (and growing) number of people
are dependent on coral reefs
•Management of a multispecies fishery is
extremely complex, and often fails
•Terrestrial development may destroy
coastal reef systems
•Global climate change may exert new
pressures

79. How can we protect Corals from
bleaching?
•Not to touch corals physically.
•Stop destructive actions such as dynamite fishing,
over coastal development causing sedimentation.
•Have an interest on coral reef and take actions to
spread knowledge.
•Proper instruction for any people trying to play
around coral reefs.

80. Reef Survival
Future Solutions:

81. Marine Protected Areas (MPA’s)
•MarineProtectedAreasdescribe
areasorregionswhichhavebeen
placedundersomerestrictionsinthe
interestedofprotectingthe
environment.
•MPA’sdonotnecessarilyrestrictall
humanactivity,butinsteadplace
limitationsonwhatactivitiesare
allowed,forexamplefishing,fishing
seasons,catchlimits,etc.
•MPA’sincludeavarietyofreefs,but
maynotbeasustainablesolutionfor
thefuture.

82. •Integratingcoastalzonemanagement
•Effectiveenvironmentallaws
•Educatingpolicymakersandthepublicabout
howreefhabitatsshouldbemaintained
•Promotingenvironmentallysoundpractices
forlanduse
•Minimizingillegalfishinganddeveloping
sustainablefisheries
•Developingdisasterstrategies

83. Here is a good example of a live coral.

84. Reefs grow when calcium
containing sediments are
deposited in spaces between coral.
As encrusting coralinealgae
“glues” the sediments together,
new “live rock” is formed.

85. Once this Halimeda(calcareous green algae) dies, 95% of what
remains will be sediment and real estate for new coral
colonies.
Coral benefits from the death of other organisms.

86. From this…

87. To this….
Temperatureincreases and competitionfrom red algae have killed
much of this coral reef.

88. Diseaseis another major factor limiting growth. Here is
an example of elkhorn coral (Acropora palmata) infested
by “white band disease.”

89. Food Webs: Same concept, more complexity

90. It’s up to Us to Save Coral Reefs
Be Responsible.