Peracarida crustacean populations of the artificial hard-substratum in N. Michaniona (N. Aegean)

Quantitative samples were taken during summer and winter in two successive years from artificial substrata at one site (N. Michaniona) in Thermaikos Gulf. Sampling was carried out using a specially designed sampler. Data were analyzed with common biocoenotic methods and non-parametric statistical tests. The examination of approximately 10,500 specimens revealed the presence of 17 peracaridan species, the most dominant of which were Corophium acutum (41\%), Leptochelia savignyi (24\%), Corophium sextonae (14\%) and Elasmopus rapax (12\%). All the species are very common and have been reported in many sites and assemblages in the N. Aegean and W. Mediterranean Sea. Shannon index, which was calculated separately for each sample, had similar values in the same year (2.04-2.44 in 1994 and 1.30-2.00 in 1995). Comparison of the samples, on the basis of their abundance and their diversity using Kruskal-Wallis test, showed significant differences among them (p < 0.05). Mann-Whitney test was used to find out the differences among the samples. Samples were grouped according to their similarity employing Euclidean distances and Ward's method. The total of the examined samples demonstrated that the composition of the peracarida fauna in the region of N. Michaniona, was similar to peracarida fauna of photophyllic algae assemblages. The results of this research must be considered essential to the biomonitoring of Thermaikos Gulf.