Coral Reef Coasts

Coral reef coasts occur almost entirely between the Tropics of Cancer and Capricorn, though functional exceptions involving fossil reefs may extend beyond these limits. The reef component of a coral reef coast is constrained by the physiological requirements of the corals themselves, which include clear, warm water, neither too fresh from river outflows (>30 ppt) nor too saline from high evaporation (<40 ppt), with a temperature range of between about 15–30 °C, and not heavily sedimented. Exposure levels are rarely limiting; corals thrive from very sheltered to extremely exposed conditions.

Because reefs grow vertically to the low tide level, they provide very effective shelter to the coast, which in turn greatly affects the habitats which lie in their lee. The more closely a reef is located to the coastline, the greater the shelter will be. Extremely sheltered coasts lie behind fringing reefs with broad reef flat components, over which water always remains <1–2 m deep. Reef...