Community structure of the sessile biota on five artificial reefs of different ages

Patterns of sessile epibenthic community structure were examined on five artificial reefs (sunken vessels) ranging in age from 3.5 to 10.0 years. The reefs were located off South Carolina and Georgia in 22to 31-m depths. Photographic and removal sampling techniques were used to study the communities. Results indicated that there were no consistent trends in biomass, percent cover, or number of sessile species with increasing age of the artificial reefs; however, all three variables were significantly greater on vertical than on horizontal surfaces. Differences between surface orientations may have been due to heavier predation or greater sedimentation on horizontal surfaces. Alternatively, negative phototactic behavior of settling larvae may have favored the colonization of more shaded vertical surfaces. Other differences in the sessile biota among reefs appeared to be related to the proximity of natural hard-bottom habitat, and to the possibility of having sampled surfaces treated with antifouling paint on one of the reefs. The absence ofIarge sponges and corals (which are common in adjacent hard-bottom habitats) from all reefs examined in this study suggests two possibilities: I) either the substrate provided by these artificial reefs is intrinsically different from that of natural hard bottom or 2) these particular organisms are late colonizers or slow to