Coral Reef Ecosystems
What is a coral reef?
Coral reefs are the most biologically diverse marine eco-systems on
earth, rivaled only by the tropical rainforests on land. Corals grow
over geologic time and have been in existence about 200 million years.
Corals reached their current level of diversity 50 million years ago.
The delicately balanced marine environment of the coral reef relies on
the interaction of hard and soft corals, sponges, anemones, snails,
rays, crabs, lobsters, turtles, dolphins and other sea life.
What is a coral reef made of?
A coral reef is composed of thin plates or layers of calcium carbonate
secreted over thousands of years by billions of tiny soft bodied
animals called coral polyps. It takes years for some corals to grow an
inch and they range in size from a pinhead to a foot in length. Each
polyp excretes a calcereous exo-skeleton and lives in a symbiotic
relationship with a host algae, zooxanthellae, that gives the coral
its color. Zooxanthellae takes in carbon dioxide, process is through
photosynthesis, and then gives off oxygen as a by-product that is used
by the host polyp. Millions of polyps grow on top of the limestone
remains of former colonies to create the massive reefs. Yet these tiny
animals form the only natural formation visible from outer space.
More about corals
Corals are divided into two kinds and both are stationary on the ocean
bottom. Hard corals such as brain, star, staghorn, elkhorn and pillar
corals have rigid exoskeletons, or corallites, that protect their soft
delicate bodies. Gorgonians, or soft corals, such as sea fans, sea
whips, and sea rods, sway with the currents and lack an exoskeleton.
Coral reefs depend upon mangroves and sea grasses
Mangroves are salt-tolerant trees with submerged roots that are a
nursery and breeding ground for birds and most of the marine life that
migrates to the reef. Mangroves trap and produce...