The sub-fossil red coral of Sciacca (Sicily Channel, Mediterranean Sea): colony size and age estimates

The Mediterranean red coral, Corallium rubrum (L.), has been a valuable economic resource for more than 2000 years. TheSicily Channel and surrounding areas are one of the most famous red coral fishing grounds of the whole region, hosting thedeepest ever found living colonies and large sub-fossil red coral deposits; the so-called Sciacca banks are a unique location inthe whole Mediterranean Sea. In this paper, a morphometric description of this sub-fossil population is presented for the firsttime from studies of colonies in the collection of several coral factories from Torre del Greco (Naples), with radiocarbon ageestimations and growth rate evaluations. From the results of this study, after several thousand years Sciacca red coral coloniesmaintained the organic matrix structure with evident annual discontinuities, allowing estimations of the annual growthrate (about 0.3 mm/year) and the average population age (about 33.5 years). These resulting data are similar to the valuesdetermined for deep-dwelling living red coral populations. The radiocarbon dating evidenced a range of ages, from 8300to 40 years before 1950 CE, mostly falling between 2700 and 3900 YBP, suggesting that colonies accumulated over a widespan of time. In view of the tectonically active nature of the area, several catastrophic events affected these ancient populations,maintaining them in a persistent state of early-stage, structurally similar to the those in current over-exploited areas.