Coral Reefs

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Coral Reefs
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Location of Reefs

• Found between 30north and 30south
• Reason coral reefs do not thrive in areas where
  the surface temperature is below 70F
• Two areas of coral reefs
• Continental
• Oceanic
• Indian
• Pacific

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Types of Reef

• Barrier
• Offshore, and separated by a lagoon
• Atol
• Deep ocean, volcanic foundations
• Fringing
• Simplest built upwards and outwards in shallow
  seas, beside islands or continents

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Formation of Reefs

• Built of entirely marine plants and animals
• Material is calcium carbonate limestone derived
  from the surrounding waters by reef organisms
• Reef is a veneer on which new limestone can
  attach
• The sea level limits the upward growth of the
  reef
• Reefs have only existed for a relatively short
  amount of time in geological terms

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Corals

• Both living and dead, they form a framework
• Solid and unyielding or soft but firmly attached
• Form into mounds, plates, branches or crusts
• Are coelenterata along with jellyfish and sea
  anemones
• Special prey catching cells - nematocysts
• Colonial single founder individual, dividing to
  replicate itself over and over again
• Zooxanthellae tiny single celled
  photosynthesising plants amongst within coral
  tissues

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Plankton

• Too small to be seen, and are transparent
• ZOOPLANKTON
• Gelatinous
• Some predators, others produce fine mesh for
  collecting food, some produce mucus house
• PHYTOPLANKTON
• Microscopic in size
• Photosynthetic

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Algae and Seagrasses

• Important biological component of coral reefs
• 500 species of seaweed and 12 species of sea
  grasses in the Great Barrier Reef
• All marine flowering plants are known as sea
  grasses
• They have male and female parts
• Able to pollinate while submerged in sea
• Known as hydrophilous pollination
• Non-flowering marine plants are known as
  algae/seaweed

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Sponges

• Important role in complex structural processes
• Chemically digest the limestone skeletons which
  go on to form the base of the coral reef
• Efficient vacuum cleaners
• Filter out bacteria, detritis and coral mucus

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Marine Worms

• Brightly coloured, voracious jaws, well developed
  eyes
• Exist within dead coral skeleton
• Bore by chemically dissolving coral
• Range from microscopic to several cms in length

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Molluscs

• 4 major groups
• Gastropods seasnails, slugs
• Bivalves oysters, scallops, clams
• Cephalopods octopus, squid
• Chitons molluscan equivalent of
  terrestrial armadillo
• Soft bodied with a hard outer shell
• Found in coastal zones

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Crustaceans

• Reefs abound with brilliantly coloured
  crustaceans
• Most live in hiding only come out at night to
  feed
• Exoskeleton gives protection
• Female lays eggs which remain attached until
  developed
• Live in permanent symbiotic relationship with
  coral
• Provides shelter, protection and food

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Bryozoans

• Hidden areas of reef encrusted with moss-like
  bryozoans
• Often most dominant life form
• Grow on rigid surfaces, moving objects or are
  free living in the water

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Echinoderms

• Most conspicuous creatures on the reef
• E.g. sea urchins, starfish, cucumber
• 6000 species
• Almost all bottom dwelling
• Have a sessile lifestyle, and are suspension
  feeders, but some are carnivorous

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Ascidians

• Filtering water bags
• E.g. seasquirts
• Two important roles
• Feed in the water around the reef and keep it
  clean
• Concentrate the plankton in the water making it
  available for other animals
• Sessile lifestyle fixed firmly to substrate
• Cilia set up water current to allow filter feeding

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Fishes

• Diverse range
• Many have evolved with the coral
• As size of fish increases the number of species
  increases and the number of individuals decreases
• Many territorial
• Adapted in shape and behaviour depending on food
  source

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• 4 types
• Grazers
• Plankton feeders
• Mollusk, crab, shrimp feeders
• Predators

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Dangerous Animals on the Reef

• Many use chemical defences
• Bacterial attack can be countered by development
  of bacteriocides
• Mechanical and chemical offensive weapons also
  abundant

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Example Portuguese Man o War

• Have toxin loaded cells
• And needle sharp barbs at end of coiled spring

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Example Sea Urchins

• Have sharp spines
• Can have a coating of venomous mucus

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Example Sea Snakes

• Have small fangs
• But with deadly venom
• Are more dangerous than land snakes

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Example Puffer Fish

• Puff up and produce strong poison
• Is called tetrodoxin

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Example Moray Eels

• Have large, hooked, razor sharp teeth

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