Combining seafloor imagery with pore water chemistry at Arctic cold seeps: a new case study from the SW Barents Sea

Abstract:

Cold seep environments are associated with high fluxes of reduced compounds promoting the development of chemosynthesis-based communities on the seafloor. Microbial consortia performing anaerobic oxidation of methane (AOM) in the sulfate-methane transition zone (SMTZ) regulate the amount of hydrogen sulfide and methane available to seep fauna. On the other hand, bioturbation and bioirrigation of the uppermost sediment layer may significantly alter the pore water chemical profiles and further stimulate methane oxidation.

We present a new case study from the SW Barents Sea (Bear Island Trough), where active methane seepage occurring at ~300 m water depth is associated with patches of microbial mats and siboglinid tubeworms on the seafloor. We generated 3D models and orthomosaics of the seafloor based on high-resolution seafloor imagery and bathymetry data. Object-Based Image Analysis (OBIA) classification technique was used for habitat mapping purposes and the obtained results were integrated with pore water sulfate data and headspace gas from sediment cores to characterize the subseafloor chemical conditions. By combining seafloor imagery with pore water geochemistry, we successfully identified different seep habitats characterized by variable depth of the SMTZ and diffusive sulfate fluxes, reflecting spatially heterogeneous upward methane fluxes. Results are compared with other studies from Arctic cold seeps.