CAGE15-2 Cruise Report: Gas hydrate deposits and methane seepages offshore western Svalbard and Storfjordrenna: Biogeochemical and biological investigations

The main goal of CAGE 15-­2 cruise was to study the gas hydrate system and methane emissions off western Svalbard and in Storfjordrenna. We addressed this through a comprehensive scientific program comprising dives with the MISO-­‐Tow Cam adapted to the multicorer frame from UiT-­‐NPI (TowCam/Multicorer, TCM), methane measurements in sediments and water column, sediment coring (multicorer + gravitycorer), water column and sediment biogeochemistry, microbiology, micropaleontology, macrobiology, and bathymetric mapping. In addition, during the ecosounder and TCM surveys we collected data for selecting the locations for the CAGE observatories to be deployed during the cruise. The areas investigated were: W Prins Karls Forland (two sites at ca 90 m and 240 m water depth),An area located at the coordinate 78N 08E called “site 7808” (ca 90 m water depth; marker CAGE 882),Vestnesa Ridge (ca 1200 m water depth; markers CAGE 888 and 895),Storfjordrenna (two sites at ca 350, benthic station SR1, and 390 m water depth, Pingos site; marker CAGE 933),Craters area (ca 350 m water depth). We planned the following activities during the CAGE 15-­2 cruise: EM 300 Simrad swath bathymetry mapping to identify seabed morphologyMapping of flare distributionsCTD stations at different water depths and in different areas for measurements ofocean water masses characteristics, andwater sampling for water/gas chemistry and microbiology investigations across methane seeps.TCM surveys (video-­‐camera) to image seabed fluid flow expressions, sites of bacteria mats and gas bubbles. These results were used to define sampling stations and collect data for the future deployment of CAGE observatories (cruise CAGE15-­‐3)Repeated deployments with TCM to sample surficial and shallow sediments with respect to microbiology, geochemistry, biogeochemistry, and micropalentology.Gravity corer for studying sediment biogeochemistry, biomarkers, microbiology, and foraminifera.Van Veen grabs sampling for studying macrofauna.Scrape sampling to collect fauna communities and possible carbonate blocks. The cruise may be known as: CAGE15_2