Growth and population dynamics model of the Mediterranean solitary coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

Complex life history processes of corals, such as fission, fusion, and partial mortality of colonies, that decouple coral age from size, are rare or clearly detectable in corals that produce distinct colonial or solitary forms. In some of these corals, individual age may be determined from size, and standard age-based growth and population dynamics models may be applied. We determined population size and structure and measured growth rates of Balanophyllia europaea individuals at Calafuria in the eastern Ligurian Sea. We then applied demographic models to these data. Growth rate decreased with increasing coral size. The age–size curve derived from field measurements of growth rates fits that obtained from the computerized tomography analysis of skeletal growth bands. The frequency of individuals in each age class decreased exponentially with age, indicating a population in a steady state. The survival curve showed a turnover time of 3.6 years and a maximum life span of 20 years. This is nearly three times the turnover time and maximum life span recorded for Balanophyllia elegans living off the western coasts of North America, the only congeneric species whose population dynamics has been studied. The Beverton and Holt population model may be useful for comparative analyses of demographic traits and for resource management of solitary or compact, upright growth forms that rarely fragment. This paper completes the description of the main life-strategy characteristics of the Mediterranean endemic coral B. europaea, together with our previous studies on the reproductive biology of this species. This constitutes a major advance in the understanding of the biology and ecology of Mediterranean scleractinian corals, and represents the most complete description of a coral from this geographic area to date that we are aware of.