A trawl retrieval of nearly two tons of organisms and shell debris in 500m of water at a location of known natural petroleum seepage in the Gulf of Mexico in 1984 marked the beginning of four years of interdisciplinary studies (Kennicutt et al., 1985). It was soon recognized that the assemblage of organisms recovered was similar to that reported at the hydrothermal vents and the Florida Escarpment (Corliss and Ballard, 1977: Paull et al., 1984). These and other discoveries have now become referred to as the contrasting ecological niches of “hot vent” and “cold seep” communities. Hot vent areas are characterized by elevated temperatures caused by the recirculation of seawater through zones heated by magmatic intrusions. No temperature anomalies are apparent at the cold seep sites, but they have in common with hot seeps a supply of reduced compounds that creates a tenuous balance between oxic and anoxic conditions (Paull et al., 1984; Cavanaugh, 1985). Early studies at both types of sites revealed that the enhanced productivity and biomass of these communities was directly linked to symbiotic relationships between bacteria and invertebrates. The Gulf of Mexico petroleum seep sites are in relatively shallow water, which allows for extensive and repeated samplings as well as maintenance of living organisms at shore-based laboratories. The Louisiana seep organisms require water temperatures of 5-7°C and a supply of reduced compounds and dissolved oxygen for their survival in the laboratory.