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 picoand 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 μg 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 μg 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.