Variation in biometry and population density of solitary corals with solar radiation and sea surface temperature in the Mediterranean Sea
The correlation between two environmental factors (solar radiation and sea surface temperature), biometry, and population density was assessed along a latitudinal gradient in the zooxanthellate coral Balanophyllia europaea and in the azooxanthellate coral Leptopsammia pruvoti. With increasing polyp size, the oral disc of B. europaea assumed an oval shape, while that of L. pruvoti retained a circular shape. In both species, biometric parameters varied more with temperature than with solar radiation. In the zooxanthellate species, temperature explained a higher percentage of biometric parameter variance than in the azooxanthellate species. While environmental factors did not co-vary with demographic characteristics in L. pruvoti, temperature was negatively related to the population density of B. europaea. It is hypothesized that the negative effect of temperature on biometry and population density of B. europaea depends on photosynthesis inhibition of symbiotic zooxanthellae at high temperatures, which would lower the calcification rate and availability of energetic resources.
KeywordsCoral Growth Polyp Size Biometric Parameter Skeletal Density Skeletal Mass
We wish to thank L. Bortolazzi, M. Ghelia, G. Neto, and L. Tomesani for their underwater assistance in collecting the samples. The diving centers Centro Immersioni Pantelleria, Il Pesciolino, Polo Sub, and Sub Maldive supplied logistic assistance in the field. The Bologna Scuba Team collaborated in the underwater activities. The Marine Science Group (http://www.marinesciencegroup.org) supplied scientific, technical, and logistical support. H. R. Lasker, J. Bilewitch, and N. Kirk (State University of New York at Buffalo), N. E. Chadwick-Furman (Auburn University), and two anonymous reviewers gave comments that improved the manuscript. This research was financed by the Associazione dei Tour Operator Italiani (ASTOI), the Marine and Freshwater Science Group Association (http://www.msgassociation.net), the Canziani foundation of the Department of Evolutionary and Experimental Biology of the Alma Mater Studiorum—University of Bologna, and the Ministry of Education, University and Research (MIUR). The experiments complied with current Italian law.
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