EFFECTS OF DIVER FREQUENTATION ON MEDITERRANEAN SUBLITTORAL POPULATIONS OF THE BRYOZOAN PENTAPORA-FASCIALIS

The erect, foliaceous bryozoan Pentapora fascialis was selected as an indicator of the abrasive effects of heavy diving activity in Mediterr anean coralligenous communities. A comparative survey of bryozoan popu lations at diver-frequented and unfrequented sites was undertaken in t he Medes Islands Protected Area (NW Mediterranean) in 1992. Density, c olony diameter, and colony height of P. fascialis populations were sig nificantly lower and colony position was more cryptic at frequented si tes than at unfrequented sites. Human frequentation may affect not onl y the structure of P. fascialis populations, but also that of the cora lligenous community as a whole.