BICD 2005BICD 2005

An Introduction to Coral An Introduction to Coral ReefsReefs

Bay Islands College of Diving, UtilaBay Islands College of Diving, Utila

BICD 2005BICD 2005

ContentsContents

• Animal or Plant?Animal or Plant?

• What is a coral?What is a coral?

• Location and limitationsLocation and limitations

• Reproduction Reproduction

– – Sexual and AsexualSexual and Asexual

• Reef ClassificationReef Classification

• Components of the Reef Components of the Reef EcosystemEcosystem

• Reef ZonationReef Zonation

• Main Groups of CoralMain Groups of Coral

• SummarySummary

BICD 2005BICD 2005

Animal or Plant?Animal or Plant?

• In 1753, J. A. de Peysonell proved corals were animals rather than In 1753, J. A. de Peysonell proved corals were animals rather than plants.plants.

• All corals are classified under the All corals are classified under the PhylumPhylum CnidariaCnidaria..

• Other members of group: hydroids, jellyfish and anemones.Other members of group: hydroids, jellyfish and anemones.

• All Cnidaria have stinging cells called All Cnidaria have stinging cells called nematocystsnematocysts. They are . They are located on their tentacles and are used for:located on their tentacles and are used for:– Capturing preyCapturing prey– DefenceDefence

• Usually the stings from these corals cause no harm to divers with the Usually the stings from these corals cause no harm to divers with the exception of fire corals which can cause a small irritation.exception of fire corals which can cause a small irritation.

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What is a coral?What is a coral?• ANATOMY:ANATOMY:

– A cup-shaped body, with a A cup-shaped body, with a single, central opening that single, central opening that is surrounded by tentacles.is surrounded by tentacles.

– The opening acts as a mouth The opening acts as a mouth as well as an anus.as well as an anus.

• DIFFERENT APPEARANCES:DIFFERENT APPEARANCES:

– PolypsPolyps: solitary or colonial.: solitary or colonial.

– Unattached, free swimming Unattached, free swimming medusamedusa or jellyfish. or jellyfish.

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What is a coral?What is a coral?

• There are 2 main types of coral:There are 2 main types of coral:

– Reef building (Reef building (hermatypichermatypic))

– Non-reef building (Non-reef building (ahermatypicahermatypic) )

• Reef builders have massive skeletons and are the majority Reef builders have massive skeletons and are the majority of the basic framework of the reef.of the basic framework of the reef.

• The coral polyps act as building blocks, and coralline algae The coral polyps act as building blocks, and coralline algae acts like cement which holds the whole structure together.acts like cement which holds the whole structure together.

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Location and limitationsLocation and limitations

• Found throughout the world in tropical waters where:Found throughout the world in tropical waters where:

• Water temperatureWater temperature needs to be above 18.5 needs to be above 18.5C (approx 70-85C (approx 70-85C). C).

• There the water is subject to There the water is subject to movementmovement. .

• Corals can only live within the Corals can only live within the euphotic zoneeuphotic zone (0-90m). (0-90m).

• Water clarityWater clarity – allows beams to light to reach the single celled – allows beams to light to reach the single celled algae called algae called zooxanthellaezooxanthellae which live within the tissues of the which live within the tissues of the coral polyp.coral polyp.– Symbiosis:Symbiosis:

– Algae provides oxygen and glucose.Algae provides oxygen and glucose.– Coral provides carbon dioxide, and shelter.Coral provides carbon dioxide, and shelter.

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Location and limitationsLocation and limitations

• Hermatypic corals gain over 80% of this energetic intake Hermatypic corals gain over 80% of this energetic intake from this relationship with the algaefrom this relationship with the algae

• Coral growth even in pristine conditions is usually less than Coral growth even in pristine conditions is usually less than

1 inch per year for most species1 inch per year for most species • Other requirements: sufficient salinity, wave action and a Other requirements: sufficient salinity, wave action and a

firm base for attachment firm base for attachment

• Different species vary in their resistance to each of these Different species vary in their resistance to each of these factors, so a zonation pattern will result factors, so a zonation pattern will result

• These conditions are required to keep the rate of deposition These conditions are required to keep the rate of deposition (new growth) greater than of the erosion and dissolution (new growth) greater than of the erosion and dissolution

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Reproduction - SexualReproduction - Sexual• Definition: genetically new individuals formed from the combination of Definition: genetically new individuals formed from the combination of

male and female genes produced by different parental colonies male and female genes produced by different parental colonies ((genetic recombinationgenetic recombination).).

• Coral species have:Coral species have:– Separate male and female colonies, or;Separate male and female colonies, or;– Colonies can be hermaphroditic.Colonies can be hermaphroditic.

• Fertilized eggs - inside a colony or outside in open water. Fertilized eggs - inside a colony or outside in open water.

• Spawning techniquesSpawning techniques– BroodersBrooders– Broadcast SpawnersBroadcast Spawners

• Develop into Develop into planula larvaeplanula larvae – disperse - settle on hard substrate in – disperse - settle on hard substrate in clear shallow water and begin producing a tiny calcium skeleton.clear shallow water and begin producing a tiny calcium skeleton.

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Reproduction - AsexualReproduction - Asexual• Definition - the development of genetically identical clones without Definition - the development of genetically identical clones without

the union of male and female gametes. the union of male and female gametes.

• Advantage is that the new colony is more likely to succeed Advantage is that the new colony is more likely to succeed than Planular Larvaethan Planular Larvae

• Disadvantage is that the new colony is cloned and therefore Disadvantage is that the new colony is cloned and therefore susceptible to the same diseases as the parent colonysusceptible to the same diseases as the parent colony

• Two main ways:Two main ways:– Budding Budding (Extratentacular budding) (Extratentacular budding)

• The polyps bud off a from the side creating a new polypThe polyps bud off a from the side creating a new polyp

– Fission Fission (Intratentacular budding) (Intratentacular budding) • Polyps split into half through the tentacles creating the new Polyps split into half through the tentacles creating the new

polyppolyp

• New colonies can also form by New colonies can also form by fragmentationfragmentation– Broken pieces of a colony fall off and reattach themselves to the Broken pieces of a colony fall off and reattach themselves to the

substratesubstrate

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Reef ClassificationReef Classificationa)a) Fringing Reef (youngest)Fringing Reef (youngest)

b)b) Barrier Reef – e.g. Barrier Reef – e.g. The Mesoamerican Barrier Reef The Mesoamerican Barrier Reef

c)c) Atoll (oldest)Atoll (oldest)

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Components of the Reef Components of the Reef EcosystemEcosystem• MangrovesMangroves - - stands of vegetation with a stands of vegetation with a

terrestrial ancestry.terrestrial ancestry.

• Grow in sandy and muddy waters around the Grow in sandy and muddy waters around the coasts, areas which are generally saline and coasts, areas which are generally saline and anoxic.anoxic.

• In the Caribbean, mangroves form a In the Caribbean, mangroves form a vital partvital part of of

the ecosystem, linked with the lagoon and reef the ecosystem, linked with the lagoon and reef habitats.habitats.

• Mangroves actively uptake and utilise nutrients, Mangroves actively uptake and utilise nutrients, therefore act as recyclers mobilising nutrients. therefore act as recyclers mobilising nutrients.

• Mangroves actively uptake and utilise nutrients, act as recyclers mobilising Mangroves actively uptake and utilise nutrients, act as recyclers mobilising nutrients.nutrients.

• Grow in areas low in oxygen and actively increase levels through Grow in areas low in oxygen and actively increase levels through photosynthesis.photosynthesis.

• Provide a number of habitats for a variety of organisms to live and feedProvide a number of habitats for a variety of organisms to live and feed

• Particularly important as a nursery ground.Particularly important as a nursery ground.

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Components of Components of the Reef the Reef EcosystemEcosystemLagoons-Lagoons-

• Lagoons are one of the most important and extensive habitats of coastal Lagoons are one of the most important and extensive habitats of coastal waters, they occur in protected areas and are primarily covered with seagrass waters, they occur in protected areas and are primarily covered with seagrass beds on sandy, silty or rubble substratum.beds on sandy, silty or rubble substratum.

• Seagrass beds, large proportion of primary production, Seagrass beds, large proportion of primary production, physically causes physically causes sediment to settle out of the water column.sediment to settle out of the water column.

• Provides food for herbivores and indirectly carnivores up the food chain.Provides food for herbivores and indirectly carnivores up the food chain.

• Lagoons offer a soft sandy substrate and the surface of seagrass blades as Lagoons offer a soft sandy substrate and the surface of seagrass blades as different habitats for many species to exploit.different habitats for many species to exploit.

• Animals live in/on the sandy/muddy bottom (Animals live in/on the sandy/muddy bottom (benthic formsbenthic forms), ), • On plants (On plants (epiphytic formsepiphytic forms),),• In water surrounding plants (In water surrounding plants (epibenthic or pelagic formsepibenthic or pelagic forms).).

• As lagoons are sheltered by the reef their waters are relatively calm, As lagoons are sheltered by the reef their waters are relatively calm, encouraging fragile species or ones preferring calm conditions. (e.g. Sea encouraging fragile species or ones preferring calm conditions. (e.g. Sea turtles, molluscs, urchins and manatees)turtles, molluscs, urchins and manatees)

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Components of the Reef Components of the Reef EcosystemEcosystemCoral ReefsCoral Reefs

• Biogenic limestone reefs which are Biogenic limestone reefs which are geologic structures built over time by geologic structures built over time by living organisms. living organisms.

• They bring high productivity to areas They bring high productivity to areas which otherwise would be relatively which otherwise would be relatively unproductive.unproductive.

• High species diversity is also an High species diversity is also an

important defining feature of coral reefs. important defining feature of coral reefs. There are an amazing array of habitats, There are an amazing array of habitats, food, shelter, living space and substrate food, shelter, living space and substrate for a huge number of species.for a huge number of species.

• • Coral reefs are considered as an Coral reefs are considered as an

ecologically stable environment. This fact ecologically stable environment. This fact has resulted in evolutionary has resulted in evolutionary specialisation. specialisation.

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Components of the Reef Components of the Reef EcosystemEcosystem

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Reef ZonationReef Zonation

• Physical and biological features Physical and biological features of the zones are controlled by of the zones are controlled by a range of factors, wave a range of factors, wave action, and photic levels.action, and photic levels.

• Back ReefBack Reef - consists of patch - consists of patch reefs, rubble areas and a reefs, rubble areas and a carbonate platform. carbonate platform.

• Relatively low diversity as Relatively low diversity as suspended particles deposit.suspended particles deposit.

• Species which exist there are Species which exist there are more resilient to more resilient to sedimentation. But require a sedimentation. But require a lot of light.lot of light.

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Reef ZonationReef Zonation• Reef CrestReef Crest -- Top of the reef system.Top of the reef system.

• Reef can break the water’s surface Reef can break the water’s surface at low tide. at low tide.

• Greatest physical stress, pounded Greatest physical stress, pounded by incoming waves, species strong by incoming waves, species strong to dissipate wave action. to dissipate wave action.

• Species grow fast and regrow if they Species grow fast and regrow if they are broken away from their primary are broken away from their primary structure. structure.

• Commonly a lot of coralline algae Commonly a lot of coralline algae

which holds the reef together, fire which holds the reef together, fire coral and colonial zoanthids. coral and colonial zoanthids.

• Large mono-specific stands likely.Large mono-specific stands likely.

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Reef ZonationReef Zonation• ForereefForereef - Major reef zone in - Major reef zone in

Caribbean waters.Caribbean waters.

• Shallow, but high in energy where Shallow, but high in energy where oceanic waters meet the reef. oceanic waters meet the reef.

• Reef slopes downward at an angle Reef slopes downward at an angle less than 45less than 45 and eventually the and eventually the physical force of waves is reduced.physical force of waves is reduced.

• Species diversity reaches a maximum Species diversity reaches a maximum around 20m where corals find the around 20m where corals find the optimum location which balances low optimum location which balances low wave action and relatively high light wave action and relatively high light levels. levels.

• But this is also where competition is But this is also where competition is at its highest for available resources.at its highest for available resources.

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Reef ZonationReef Zonation• DropDrop--offoff - Forereef becomes - Forereef becomes

a steeper slope or wall at a steeper slope or wall at greater than 45greater than 45 where it where it continues to the depths of continues to the depths of the ocean. the ocean.

• Corals become restricted by Corals become restricted by light, so numbers are light, so numbers are reduced. reduced.

• Morphology is also adapted Morphology is also adapted

to present a larger surface to present a larger surface area to increase the ability to area to increase the ability to absorb lower levels of light. absorb lower levels of light.

• Corals can also have a more Corals can also have a more fragile structure due to the fragile structure due to the severely reduced wave severely reduced wave action. action.

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Main Groups of CoralMain Groups of Coral

• There are 4 main groups of coral:There are 4 main groups of coral:

• Class: Hydrozoa (hydrozoans) – “Fire Corals”Class: Hydrozoa (hydrozoans) – “Fire Corals”

• Class: Anthozoa – Subclass: Octocorallia (octocorals) Class: Anthozoa – Subclass: Octocorallia (octocorals) – “Soft Corals”– “Soft Corals”

• Class: Anthozoa – Subclass: Hexacorallia (hexacorals) Class: Anthozoa – Subclass: Hexacorallia (hexacorals) – “Stony/Hard Corals”– “Stony/Hard Corals”

• Class: Anthozoa – Subclass: Ceriantipatharia – Order: Class: Anthozoa – Subclass: Ceriantipatharia – Order: Antipatharia (antipatharians) – “Black Corals”Antipatharia (antipatharians) – “Black Corals”

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SummarySummary

• Animal or Plant?Animal or Plant?

• What is a coral?What is a coral?

• Location and limitationsLocation and limitations

• ReproductionReproduction– Sexual and AsexualSexual and Asexual

• Reef ClassificationReef Classification

• Components of the Components of the Reef EcosystemReef Ecosystem

• Reef ZonationReef Zonation

• Main Groups of CoralMain Groups of Coral