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Coral%20Reefs

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Coral Reefs. What is a coral reef? Habitat forming scleractinians. Different ... Conch, bivalves, octopus, squid.... Food for pelagic fish species. Limestone ... – PowerPoint PPT presentation

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Title: Coral%20Reefs


1
29 April 2008OCN 621 Biological Oceanography
  • Coral Reefs
  • What is a coral reef?
  • Habitat forming scleractinians
  • Different types of reef
  • Symbiosis
  • Biogeography
  • Controls on Biogeography
  • The value of reefs

2
What is a coral reef?
  • Reef
  • Feature lying beneath the surface of the water
    with which a boat could get stuck on
  • Typically diverse assemblage of habitat forming
    scleractinians
  • Mainly Shallow
  • Butnot always
  • Important engineers
  • Biodiversity
  • Rain forests of the ocean
  • Cover less than 1/10 of ocean floor
  • Habitat for 25 of all marine species

3
What is a coral reef?
  • Scleractinians (primarily)
  • Other organisms also produce calcium carbonate
    structures
  • Forminifera, cocolithophores, pteropods,
    halimeda, red algae, soft coral spicules, sponge
    spicules
  • Reef structure is cemented together by calcareous
    red algae or by lithification
  • Organisms creating non-carbonate skeletons
  • Chitin, silica, gorgonin
  • Octocorals, sponges

4
Coral Reefs of the World
  • Great Barrier Reef, Australia
  • Largest coral reef in the world, 2600km
  • Belize Barrier Reef
  • Second largest in the world
  • New Caledonia Barrier Reef
  • Second longest double barrier reef 1500km
  • Andros Barrier Reef
  • 3rd largest barrier reef, 167km long and 64km
    wide
  • Red Sea Coral Reef
  • Egypt Saudi Arabia
  • Pulley Ridge
  • Florida, Deepest photosynthetic coral reef, 60m
    deep

5
Scleractinian morphology
  • Branching
  • Often fast growing
  • Plate-like
  • Often found in deeper environments
  • Massive/lobed
  • Generally slower growing, k-selected
  • Encrusting
  • Sometimes parasitic

6
Branching
7
Plate Like
8
Massive, Lobed
9
Encrusting
10
Types of Reef
  • 4 Main types of reef
  • Fringing, Barrier, Patch and Atoll
  • Also Apron, Bank, Ribbon Table
  • Fringing reef
  • a reef that is directly attached to a shore or
    borders it with an intervening shallow channel or
    lagoon
  • Bora Bora, French Polynesia

11
Bora Bora
12
Types of Reef
  • Barrier Reef
  • a reef separated from a mainland or island shore
    by a deep lagoon
  • Great Barrier Reef - Australia

13
Great Barrier Reef, Australia
14
Types of Reef
  • Patch Reef
  • an isolated, often circular reef, usually within
    a lagoon or embayment
  • Outer edge of each patch reef is surrounded by a
    halo of sand that extends out to adjacent
    seagrass beds.
  • The width of this ring of sand is determined by
    the distance that herbivorous fish feel is within
    safe foraging range from the reef.
  • Florida

15
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16
Types of Reef
  • Atoll Reef
  • a more or less circular or continuous barrier
    reef extending all the way around a lagoon
    without a central island
  • Midway, Hawaiian Islands

17
Midway
Maldives
18
Atoll Formation
  • Island erosion
  • Island sinking
  • Reef accretion

19
Reef Zones
20
Symbiosis
  • Photosynthetic algal endosymbionts
  • Dinoflagellates
  • Algae located in gastrodermis
  • Carbohydrates and lipids excreted by the algae
  • Protection and nitrogenous waste provided by host
  • Other marine taxa also engage in similar
    symbiosis
  • Sea anemones, jellyfish, sponges, clams, forams
  • Can provide up to 90 of corals energy

21
Symbiosis
22
Symbiosis
  • Genus Symbiodinium
  • Different species live in different corals
  • Controversial
  • Ingested by corals
  • But not digested
  • Reproduce by budding
  • 3 Life Stages
  • Vegatative
  • Cyst
  • Motile

23
Shallow water coral biogeography
  • Warm tropical climates
  • Low latitudes (30ºN to 30ºS)
  • High solar insolation
  • Warm water currents
  • Clear shallow waters
  • good light penetration
  • 30m
  • low sedimentation and turbidity
  • Oligotrophic waters
  • nutrient poor but not exclusively
  • Hard substrata

24
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25
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26
Annual Pattern of Daily Solar Insolation
27
Biogeography
28
Biogeography
  • What limits shallow coral reefs?
  • High latitude and depth
  • Temperature, chronic low temperature stress
  • Light irradiance, insufficient solar insolation
  • Aragonite (CaCO3) saturation state
  • Competition with temperate fauna

Kleypas, 1999, Grigg, 2006
29
Biogeography
  • Distinct fauna between Atlantic and Indo-Pacific
  • Lower diversity in the Atlantic
  • Younger, smaller ocean basin with less thermal
    capacity
  • North-south mountain ranges did not impede
    glacial advances during ice ages
  • More extinction events
  • But older coral genera 60 mya ?

30
Biogeography
Modified from Spalding, M. et al. 2001
31
Biogeography
  • Higher diversity in the Indo-Pacific
  • Older ocean basin with more stability through
    geological time
  • Larger body of water with more thermal capacity
  • East-west mountain ranges limited glacial
    advances during ice ages
  • But younger coral genera 30 mya ?
  • Center of diversity in the Indo-Australian
    Archipelago (IAA)
  • Diversity gradient as radial distance from center
    increases

32
Biogeography
Veron, 1995
33
Reef Value
  • Found in over 100 countries
  • Over 500 million people worldwide rely on coral
    reefs
  • Major source of food
  • Poorer countries
  • Fish and invertebrates
  • Conch, bivalves, octopus, squid.
  • Food for pelagic fish species
  • Limestone
  • Building materials, breakwaters, cement
  • Jewelry
  • Aquarium trade
  • Tourists
  • 6-10billion US tourist industry
  • Beach protection
  • Wave breaks

34
Conclusions
  • Majority of coral reefs are shallow, warm
    tropical, made from carbonate accreting species
  • Majority have photosynthetic algae
  • A reef can be in many different forms
  • Limited in latitude and depth
  • Higher diversity in the Indo Pacific
  • Reefs are worth s
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