A Coral reef is basically a sheet of living coral polyps which grow only a few millimeters a year. Millions of organisms consider a coral reef a great home because it provides several hiding places and several food sources. Reef-building coral will only grow in clear shallow sea water with tropic temperatures 20ºC.
They form symbiotic relationships with a dinflagellates referred to as zooxanthellae. This relationship provides a secure place for the zooxanthellae to live and provides photosynthetic energy for the coral. Within the coral you might also see sea sponges, green turtles, comb jellies, arrow crabs, angelfish, clams, nurse sharks, parrot fish, moray eels and spiny lobster.
Apron reef — short reef resembling a fringing reef, but more sloped; extending out and downward from a point or peninsular shore.
Fringing reef — reef that is directly attached to shore or borders it with an intervening shallow channel or lagoon.
Barrier reef — reef separated from a mainland or island shore by a deep lagoon.
Patch reef — an isolated, often circular reef, usually within a lagoon or embayment.
Ribbon reef — long, narrow, somewhat winding reef, usually associated with an atoll lagoon.
Table reef — isolated reef, approaching an atoll type, but without a lagoon.
Atoll reef — a more or less circular or continuous barrier reef surrounding a lagoon without a central island.
Learn more about the Great Barrier Reef.
Humans continue to threaten the coral reefs. Currently, pollution and over-fishing are the most serious threats to these ecosystems. Reefs are also destroyed by boat and shipping traffic. Human also use cyanide and other chemicals to capture fish that live in the reefs. These chemicals harm the reef’s ecosystem and kill the coral. Global warming and El Nino have also resulted in coral bleaching caused by an increasing in the water temperatures. It is important that the coral reefs are managed with care, because some believe that with the current conditions, almost all the the world’s coral reefs with be gone in 50 years.