Download The Coral Reef Ecosystem

Coral Reefs
Location of Reefs
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Found between 30°north and 30°south
Reason: coral reefs do not thrive in areas where the surface
temperature is below 70°F
Two areas of coral reefs
– Continental
– Oceanic
• Indian
• Pacific
Types of Reef
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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
Formation of Reefs
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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
Corals
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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
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
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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
Sponges
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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
Marine Worms
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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
Molluscs
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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’
Crustaceans
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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
Bryozoans
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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
Echinoderms
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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
Ascidians
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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
Fishes
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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
Dangerous Animals on the Reef
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Many use chemical defences
Bacterial attack can be countered by development of
bacteriocides
Mechanical and chemical offensive weapons also abundant
Example –
Portuguese Man o’ War
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Have toxin loaded cells
And needle sharp barbs at end of coiled spring
Example –
Sea Urchins
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Have sharp spines
Can have a coating of venomous mucus
Example –
Sea Snakes
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Have small fangs
But with deadly venom
Are more dangerous than land snakes
Example –
Puffer Fish
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Puff up and produce strong poison
Is called tetrodoxin
Example –
Moray Eels
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Have large, hooked, razor sharp teeth