The influence of hydrocarbon seeps on sediment macrofaunal biodiversity and functional traits

Chemosynthetic ecosystems in the Gulf of Mexico (GOM) support dense communities of seep megafaunal invertebrates that rely on endosymbiotic bacteria for nutrition. Distinct infaunal communities are associated with the biogenic habitats created by seep biota, where habitat heterogeneity and sediment geochemistry influence local macrofaunal community structure. Here we examine the variance in infaunal communities in the GOM with respect to depth, sediment geochemistry parameters, and distance to known seep habitats. Habitats were mapped based on ROV video of the seafloor. Samples were collected from three sites (AC601, GC852, and AT340) via box core in 2007 and processed for macrofauna and environmental characteristics. A majority of the taxa occurred within 50m of seep habitat, regardless of seep type (carbonate, mussel, mat). Overall, patterns in macrofaunal communities were driven by depth and differences in the distance to carbonate habitat. In contrast, variance in infaunal functional traits was best explained by depth, relative reliance on chemosynthetic productivity, and sediment grain size. Results suggest that northern GOM infaunal community structure and function are structured by factors that influence food availability and habitat heterogeneity.