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 transparent ZOOPLANKTON –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