Florida Sunset
© Cathleen Bester
|
 |
|
Factors influencing reef development include:
|
Coral reefs occur along coastlines in tropical and subtropical regions wherever environmental conditions are suitable for their development.
Corals require light to maintain their symbiotic association with zooxanthellae
courtesy U.S. Geological Survey
 |
Light
- Light levels are critical in maintaining the coral-algal symbiotic association
|
Light is critical in maintaining the symbiotic association between corals and symbiotic algae (zooxanthellae). The intensity of light greatly affects photosynthetic rates of the zooxanthellae, indirectly impacting coral growth and survival. Abundance of corals decreases rapidly with depth due to reduced light levels. In clear tropical waters, corals may live as deep as 150 feet (48 m), with very limited species found beyond that depth.
Warm water temperatures are required for coral survival
courtesy NASA
 |
Temperature
- Optimal temperature for coral growth is 73-77°F (23-25°C)
|
Seawater temperatures can be tolerated between 61-95°F (16-35°C), with optimal coral growth occurring at temperatures of 73-77°F (23-25°C). These temperatures exist throughout most of the tropics with the exception of cool water currents off the west coasts of Africa and Australia. However, where currents move warm water from the tropics towards the north, reefs can survive in subtropical regions as near Bermuda.
Water clarity is necessary for optimal coral growth
courtesy NASA
 |
Sedimentation
- Excessive sedimentation reduces available light for coral growth
|
Reefs can only develop in areas lacking nearby rivers that bring silt and freshwater into marine environments. Excessive sedimentation reduces available light, inhibiting photosynthesis by the symbiotic algae. Silt also settles on the coral surface, blocking feeding and respiration.
Corals tolerate a narrow range of salinity
courtesy National Park Service
 |
Salinity
- Corals require salinities between 30 and 40 parts per thousand
|
The amount of dissolved salts in the water is referred to as salinity and is measured in parts per thousand (ppt). Corals can tolerate a narrow range of salinities, between 30 and 40 ppt.
|
|
