Successional stages of experimental artificial reefs deployed in Vistonikos gulf (N. Aegean Sea, Greece): Preliminary results

In 1999 an artificial reef system, consisting of a protective zone (240 cubic modules) and a nucleus (9 Italian type and 9 French type artificial reefs), was constructed and deployed at cape Fanari (Vistonikos Gulf, North Aegean Sea) occupying an area of 6 Km2 (25rn depth). Samples, (8 cement plates, 35cmx35cm) were collected seasonally with SCUBA-diving from March 2000 till May 2001. Overall 46986 individuals were counted belonging to 13 classes, while 88 species were recorded. Common biocoenotic parameters (numerical abundance, frequency, mean dominance) were calculated. Shannon-Weaver index ranged from 2.509 to 3.741 and evenness from 0.388 to 0.579, both exhibiting a maximum in summertime. The analysis revealed a clear dominance of Serpulids during the first three periods and of Peracarida for the last two. Filter-feeder organisms including Pomatoceros triqueter, Spirobranchus polytrema and Corophium sextonae dominated the samples. Two-way ANOVA indicated significant differences in numerical abundance of each taxon with time. However, no differences were recorded among taxon from the top and the base of the pyramids except for Gastropods,which showed a significant increase in numerical abundance at the top blocks. Cluster analysis provided a dendrogram with 6 groups at a 73\% similarity level, 5 of which group together the replicates of each period, except one replicate, from the last period, that forms the 6th cluster. Filter-feeders appeared to be the prevailing organisms in artificial reefs communities.