The impact of fish farming activities on Posidonia oceanica meadows in the Aegean Sea have been detected using bryozoan epiphytes as indicators of disturbance. Samples were collected by SCUBA diving in September 2004 in order to compare assemblages between disturbed (I1:0-5 m; I2:5-10 m and I3:10-15 m) and control meadows (C1:0-5 m; C2:5-10 m and C3:10-15 m) located at different depths. Regarding the mean percentage coverage of bryozoans, significant differences were found between stations, leaf sides, depths and their interactions (p<0.05). Bryozoan species densely colonized the back side of adult leaves. Bantariella verticillata, Alcyonidium sp., Aetea truncata, Chorizopora brongniartii, Fenestrulina joannae were frequently observed on P. oceanica leaves. B. verticillata showed statistically significant side and station differences, while other species showed only significant side differences. Moreover, the mean coverage of Aetea truncata revealed no station or side variations. B. verticillata could be evaluated as an appropriate key species studying any environmental changes. In the impacted meadow, higher mean coverage values of the species were particularly determined on front side of the leaves. These results suggest that locality, leaf side and leaf part can influence the coverage value of epiphytic bryozoan species.