The Formation of Large Bacterial Aggregates at Depth Within the Louisiana Hydrocarbon Seep Zone

Abstract

Growth rate determinations on the individual components of size-fractionated water samples taken within the Louisiana hydrocarbon seep zone and westward of this region revealed that most of the biomass in the water was associated with particles larger than 64 μm (>60%). The aggregates in the seep zone were metabolically active and growing; whereas, 80 km to the west, the microbiota on the aggregates had negative growth rates, indicating a cessation of metabolic activity. This suggests that the raw materials for bacterial growth are the hydrocarbons, primarily methane, and that these particles may potentially provide a valuable food resource for regional benthic organisms. The large-scale geographic distribution of hydrocarbon seeps and the westward movement of water along the Louisiana slope suggest a nutritional resource capable of supporting a diverse marine heterotrophic community.