Heterotrophy in the Mediterranean symbiotic coral Cladocora caespitosa: comparison with two other scleractinian species

This experimental study assessed the grazing rates of the Mediterranean symbiotic coral Cladocora caespitosa on the 4 main food sources available in its natural environment: detrital particulate organic matter (DPOM) and pico-, nano-, and microzooplankton. These rates were compared to the rates of 2 other scleractinian symbiotic species, the Mediterranean coral Oculina patagonica and the tropical coral Turbinaria reniformis. Results showed that C. caespitosa was the species with the highest grazing rates of pico- and nanoplankton, which contributed to more than half of the carbon supplied by photosynthesis. The daily heterotrophic carbon (C) input from these prey (at in situ concentrations) was 88.3 +/- 22.9, 16.9 +/- 8.2, and 17.6 +/- 4.3 mu g C cm(-2) d(-1) for C. caespitosa, O. patagonica, and T. reniformis, respectively, corresponding to a percent contribution of heterotrophically acquired C to daily animal respiration (CHAR) of 119.8, 28.7, and 15.9%, respectively. C. caespitosa was also able to derive a significant part of its carbon needs from the grazing of microzooplankton and DPOM. Indeed, considering the in situ concentrations, the daily heterotrophic C input from microzooplankton and DPOM would be 32.6 and 10.0 mu g C cm(-2) d(-1), giving a CHAR estimation of 44.2 and 13.6%, respectively. Heterotrophy therefore plays a major role in the energy budget of this temperate species.