The Evolution of the Coral–Algal Symbiosis

The fossil record chronicles the rise, fall, and recovery of reefs. It is a sobering record because of the longevity of post-extinction global reef gaps and the length of time before reef recovery. Intervals when reefs are either entirely absent or greatly reduced range from 1×106 years to as much as 10×106 years in duration. The length of time for recovery has implications for the current environmental crisis. Put into the perspective of the current biotic marine crisis, the implications are bleak for the future evolution of reefs. Although evolution is not predictable, the derivation of meaningful estimates on diversity trends and rates of recovery following mass extinctions, are emerging from the fossil record. A study of the role of zooxanthellate photosymbiosis in the geologic past may provide new insights into both successes and failures on living coral reefs. The integration of biology and the fossil record offers potentials to better understand the current coral reef problems, including the bleaching phenomenon.