Coral Reef Science

Abstract

Symbiosis with zooxanthellae (symbiotic dinoflagellates) and high capacities for clonal reproduction and regeneration are important life history traits of reef-building corals. This chapter reviews the life history of reef-building corals and the symbiotic relationships between corals and their algal symbionts and discusses possible collaborative defense systems against environmental stresses as well as mechanisms of adaptation to environmental changes in coral–zooxanthella symbiotic systems. Most corals associate with one main type of symbiont, although minor or cryptic symbiont types are often detected within a colony. The association between the coral host and algal symbiont appears to be stable, and the original symbiont often returns when corals recover from bleaching. Some corals, such as the massive Porites, exhibit high fidelity to certain types of algal symbionts and still have high stress tolerance as well as long life spans suggesting the possibility that stem cells and algal symbiont cells in such long-lived colonies accumulate mutations; in turn, if cells with a higher fitness for a new environment proliferate within a colony, the colony may be able to adapt to the new environment.