Coral Reefs
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Transcript of Coral Reefs
Coral Reefs
Location of Reefs
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
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
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
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 transparentZOOPLANKTON
– Gelatinous– Some predators, others produce fine mesh for collecting
food, some produce mucus ‘house’PHYTOPLANKTON
– Microscopic in size– Photosynthetic
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
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
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
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’
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
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
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
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
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
4 types:– Grazers– Plankton feeders– Mollusk, crab, shrimp feeders– Predators
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
Example – Portuguese Man o’ War Have toxin loaded cells And needle sharp barbs at end of coiled spring
Example –Sea Urchins Have sharp spines Can have a coating of venomous mucus
Example –Sea Snakes Have small fangs But with deadly venom Are more dangerous than land snakes
Example –Puffer Fish Puff up and produce strong poison Is called tetrodoxin
Example –Moray Eels Have large, hooked, razor sharp teeth