List and describe the three types of coral reefs. What will be an ideal response?

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(1) Fringing Reefs cling to the margin of land, and connect to shore near the water surface.
Fringing reefs form in areas of low rainfall runoff primarily on the leeward (downwind side)
of tropical islands. The greatest concentration of living material will be at the reef’s seaward
edge, where plankton and clear water of normal salinity are dependably available. Most new
islands anywhere in the tropics have fringing reefs as their first reef form. Permanent fringing
reefs are common in the Hawai’ian Islands and in similar areas near the boundaries of the
tropics.
(2) Barrier Reefs are separated from land by a lagoon. They tend to occur at lower latitudes
than fringing reefs and can form around islands or in lines parallel to continental shores. The
outer edge, the barrier, is raised because the seaward part of the reef is supplied with more
food and is able to grow more rapidly than the shore side. The lagoon may be anywhere from
a few meters to 60 deep, and it may separate the barrier from shore by only tens of meters or
by as much as 300 kilometers. Coral grows more slowly within the lagoon because fewer
nutrients are available and because sediments and freshwater run off from shore. Conditions
and species within the lagoon are much different from those of the wave-swept barrier. The
calm lagoon is often littered with eroded coral debris moved from the barrier by storms.
(3) An atoll is a ring-shaped island of coral reefs and coral debris enclosing, or almost
enclosing, a shallow lagoon from which no land protrudes. Coral debris may be driven onto
the reef by waves and wind to form an emergent arc on which coconut palms and other land
plants take root. These plants stabilize the sand and lead to colonization by birds and other
species. Though an atoll’s central lagoon connects to the deep water outside through a series
of channels or grooves, coral does not usually thrive in the lagoon, both because the shallow water may become too hot from the sun or too fresh during rains and because feeding
opportunities for the coral are limited there.