Aspects of ecology of cladocora caespitosa

Abstract

Cladocora caespitosa is a temperate, zooxanthellate scleractinian coral, which is endemic to the Mediterranean Sea and adjacent Atlantic areas. This coral occurs on hard substrata in a wide range of illumination conditions, from well-lit to dim light, and at depths ranging from shallow waters, down to around 40 m. Locally, the abundance and state of health of this legally protected species appears to be declining in pristine waters; however, this aspect has not been investigated previously. Therefore, the main aim of the present investigation was to determine the occurrence and abundance of C. caespitosa colonies in local pristine waters, and to assess their state of health. During the present study, C. caespitosa was found to be more abundant in well-lit areas and colony size did not appear to bear any relationship to the depth at which the colonies were found. The present results indicated that more than half (56.8%) of the total polyps assessed were pigmented, however, the remaining polyps (43.2%) appeared to be adversely affected in some way. Most of the latter were mainly dead polyps, while bleached and partially necrotic polyps occurred in fewer numbers. The state of health of the polyps varied between localities, apparently as a result of differences in edaphic factors. This study also assessed algal growth on the colonies of C. caespitosa. A significant relationship between the number of dead polyps and algal biomass was found. It is unclear whether the polyps died as a consequence of being overgrown by the algae or if their demise was caused by other factors, and algal growth occurred subsequently. Data from the present study can be used as a baseline for further investigations on the state of the local C. caespitosa population.