Differences between subtidal epibiota on pier pilings and rocky reefs at marinas in Sydney, Australia

Epibiotic assemblages growing subtidally on pier pilings and on vertical surfaces of adjacent rocky reefs were sampled twice at a number of marinas around Sydney, Australia. As predicted, the assemblages on pilings and nearby rocks were quits distinct. Furthermore, relative differences between the two surfaces were remarkably consistent among locations and through rime, despite the fact chat the exact compositions of these assemblages differed among marinas. Assemblages on pilings were typically dominated by species of encrusting bryozoans, serpulid polychaetes, sponges and ascidians. The most common taxa on rocks were spirorbid polychaetes and filamentous and foliose algae. No one taxon was peculiar to either rocks or pilings; rather, each was found in very different proportions on the two surfaces. The results suggest that pilings at marinas are creating a habitat very different from the primary natural hard substratum (sandstone rocky reef) in these areas. Possible reasons and consequences for the differences between epibiota on pilings and rocks are discussed. (C) 1999 Academic Press.