Coral-Zooxanthellae Symbiosis: Conditions for Optimal Productivity

Temperature is also a key environmental factor influencing the productivity of zooxanthellae, as fluctuating temperatures affect their metabolic rate. This is mainly due to the effects temperature has on both the rate of photosynthesis and respiration. On studies of A. palmata corals in Jamaica, it was found that growth rates were proportional to the increase in sea surface temperature (SST). Therefore temperature also affects the corals and temperatures outside the tolerant range of a species of zooxanthellae may cause loss of the algae from the coral, leading to possible coral death. As with light, different species may be physiologically adapted to cope with varying temperature ranges, depending on their habitats.

In order to achieve a stable symbiosis between coral and zooxanthellae, the density of zooxanthellae within the coral must remain fairly constant. Usually this process is self-regulating as zooxanthellae are expelled if their reproduction rate exceeds that of the coral, and vice versa. Environmental cues are central in determining a stable symbiosis.