What conditions must be present for a coral reef to form?

Answer 1

Reef-building corals require a delicate balance of oceanographic conditions before they can occur in sufficient numbers to build reefs.

Temperature: The first of these is a seawater temperature of 16-35 °C, with optimum temperatures of 23-25 °C.

Clean water: Another condition that must be met for the development of reef-building corals is the absence of major rivers that bring silt and fresh water down to the sea. Excessive silt reduces light, thereby inhibiting photosynthesis by the symbiotic algae which are found in coral tissues. Silt may also block the mouths of corals, preventing feeding.

Light: Reef-building corals need light to support the symbiotic algae that they contain, so they cannot develop in deep water below the zone in which sufficient light is available to support photosynthesis.

Depth: Thus they are usually restricted to water depths of less than 70m. It is for this reason that coral reefs are only found adjacent to landmasses or on the summits of undersea mountains.

Inside of the coral reef structure, there is a lot of variance as to what specific condition are preferred by what types of polyps, and this is what gives us the structure for the reefs.

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Answer 2

Lots of sunlight so that zooxanthellae can photosynthesize, and a fairly steady water temperature.

Answer 3

Coral must be close to the surface of the water so that the algae, which provide food, can absorb the sunlight, warm waters, and other organisms that help, and add, to the ecosystem.