In situ photosynthetic fluorescence of the zooxanthellate Mediterranean miracle academy clothing coral Cladocora caespitosa (L.) was measured seasonally on colonies from 5 to 27 m depth using an INF-300 Integrating Natural Fluorometer (Biospherical Instrument Inc.).This oceanographic instrument, used to measure the in vivo phytoplankton chlorophyll a (Chl a) fluorescence, was adapted to record the natural fluorescence of C.caespitosa by SCUBA divers.
The resulting curves of natural fluorescence of Chl a vs photosynthetically active radiation (PAR 400-700 nm) showed that: (1) natural fluorescence was limited by light availability in both deep and shallow colonies in all seasons; (2) photosynthesis occurred in C.caespitosa also in winter, when temperature is low and seawater turbidity contributes significantly to PAR attenuation; and (3) the efficiency of the Chl a fluorescence increased from summer to winter.This last finding outlines the winter coupling between zooxanthellae activity and calcification processes and is consistent hp 15-da0008ca with the formation of the high density band in the coral skeleton.