Geological and biological aspects of hardbottom environments on the L'MANFLA shelf, northern gulf of Mexico

Side-scan sonar, underwater video, manned submersibles, and conventional surface vessel and scientific SCUBA diving operations have been combined in an interdisciplinary, multi-institutional investigation of hardbottom environments on the L'MAFLA (Louisiana-Mississippi -Alabama and Florida) shelf in the northern Gulf of Mexico. The hardbottom environments consist of: (1) moderately sloping ridges of rock rubble (e.g. nodular sideritic sandstone and mudstone) and shell hash (including bored and abraded oyster shell 1 to low-relief outcrops (e.g. dolomitic sandstone) on the inner-shelf (21 to 32 m); (2) mound-like features of bioclastic limestone on the mid-shelf (30 to 40 m); (3) calcareous reef-like pinnacles (largely composed of Lithothamnion) on the shelf break (72 to 100 m); and (4) quartose sandstone and pebble conglomerate at the head of the De Soto Canyon. Epifaunal communities on the inner-she1 f are dominated bv octocoral s (Le to or ia vir D-oto: corals and antipatharians. as well as deep' water