CoralGeography

Where are Coral Reefs Found?

Coral Reefs are typically found in a band stretching from 30° north to 30° south of the equator where the water temperature stays above 68°F year round. Because the coral relies on its photosynthesizing symbiote, zooanthellae, for food, growth occurs in areas of shallow depth and low turbidity where sunlight can reach the coral. Water movement is also important to the health of coral reefs. Tidal shifts and waves wash away waste and bring nutrients and oxygen to corals.

There are many specific environmental conditions that corals need to grow and thrive. The following outline the major ones.

• Temperature

must remain between 68-83°F, but coral productivity is highest between 74-78°F.

• Depth

most commonly less than 30 ft, but can reach several hundred.

• Emersion

most corals will die if they are exposed to open air and sunlight, but some species may survive short periods of time out of the water during extremely low tides.

• Salinity

35-38 ppt

• Turbidity

sediments causing high turbidity threaten coral survival by blocking sunlight and suffocating polyps. Corals prefer clear water.

• Bottom Topography

corals need a hard, stable substrate to anchor to. Cyanobacteria (blue-green algae) must bind sediments in muddy or sandy bottoms to form a tough, leathery mat before coral can grow.

Both the Caribbean and the Indo-Pacific have extensive regions meeting these conditions with flourishing coral reefs. The map below illustrates the current locations of reefs.

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