Photosynthesis and respiration of hermatypic zooxanthellate Red Sea corals from 5-75-m depth

Hermatypic zooxanthellate corals depend on light for photosynthesis. As such, they will not grow at depths deeper than 100 m. Submersible respirometers were used to monitor changes in oxygen concentration for five corals species, Favia favus, Fungia scutaria, Lobophyllia sp., Mycedium sp., and Stylophora pistillata. Variations in chlorophyll concentrations, zooxanthellae cell densities, photosynthesis, and respiration rates were detected in these coral species. Two clusters emerged when correlated with deep water, indicating different populations. The first group was restricted to the surface-40 m depth and the second to the 40-75-m depth. Light intensity for saturating photosynthesis E_k was less than 320 μmol q m^-2 s ^-1 for all species and decreased with depth for most of them.