Lack of detectable chemosynthesis at a sponge dominated subarctic methane seep

We used high-resolution imagery within a Geographic Information System (GIS), free gas and porewater analyses animal bulk stable isotope measurements to characterize the biotic abiotic aspects of newly discovered Vestbrona Carbonate Field (VCF) seep site on Norwegian shelf (63°28′N, 6° 31′E, ∿270 m water depth). Free was mainly composed microbial methane. Sediment sulfide concentrations were in millimolar range thus high enough sustain chemosymbiotrophic animals. Nonetheless, VCF lacked animals despite an abundance methane-derived carbonate crusts which are formed by same anaerobic processes that at seeps. Furthermore, none sampled taxa, across various trophic guilds exhibited detectable contribution chemosynthetically fixed carbon their diets based values, suggesting predominantly photosynthetic source food web. link absence highly localized methane flow pathways, may act as “shunt-bypass” oxidation (AOM) extension generation, leading sediment heterogeneous over very short lateral distances, inhibiting successful colonization seep. Instead, hosted diverse biological communities, consisting heterotrophic benthic fauna, including long lived such soft corals (e.g., Paragorgia arborea ) stony (i.e., Desmophyllum pertusum , formerly known Lophelia pertusa ). Compared surrounding non-seep seafloor, we measured heightened megafaunal density seep, attribute increased habitat heterogeneity presence variety hard substrates authigenic carbonates, dropstones coral rubble), particularly since most abundant taxa all belonged phylum Porifera. marine litter denser more variable local topography due can rip off parts bottom trawling nets thereby making catchment area for litter.