Description: The Hakon Mosby Mud Volcano (HMMV) in 1100 m water depth on the continental slope off Northern Norway was mapped with multibeam microbathymetry systems attached to the scientific ROV Victor 6000 during the ARK XIX 3/b expedition of R/V Polarstern (June-July 2003). Two multibeam systems were used: a Reson SeaBat 8125 (455 kHz, 1°x0.5°, 44 hours diving producing 235 millions of soundings) and a Simrad EM2000 (200kHz, 1.5°x3.5°, 15 hours diving producing 19 millions of soundings). Data were processed with the Ifremer CARAIBES software?, including (1) graphic and interactive ROV navigation adjustment using bathymetry as a reference, (2) roll and pitch calibration and tide correction, (3) ping editing and filtering to de-spike erroneous soundings. A final bathymetric map (grid size of 0.5 meter) has been produced using mainly Reson SeaBat 8125 data, filling the gaps with Simrad EM2000 data.We present the microbathymetric map. The seafloor morphology of the HMMV is characterized by a polygonal central body, up to 1 km across, surrounded by circular moats. The bathymetric map illustrates important seafloor features in considerable detail. The downslope and upslope edges of the central body have a NE/SW direction. This direction is also the dominant direction of a number of fractures and fissures that can be traced across the volcano. Several individual mud flows can be identified Recent mud flows all appear to originate from the central part of the mud volcano. They have formed a large flat area in the southern half of the volcano. Outside this flat area, older flows, characterized by a rough topography and a surface elevation of up to 10 m with respect to the flat area, could have been disrupted and pushed aside by the younger flows emitted at the center.The microbathymetry map provides important clues to the geological functionning of the HMMV. It puts contraints on the relative ages of seafloor compartments. It brings an essential background information for the interpretation of in situ measurements and samples.

Description: GEO-REFERENCED VIDEO-MOSAICKING AS AMEANS TO GIS-SUPPORTED SEA FLOORCOMMUNITY MAPPING AT HÅKON MOSBY MUDVOLCANOK. Jerosch (1), M. Schlüter (1), J.-P. Foucher (2)(1) Alfred-Wegener-Institute for Polar and Marine Research (AWI), Germany, (2) InstituteFrançais de Recherche pour l Exploitation de la Mer (IFREMER), FranceDuring RV Polarstern cruise ARK XIX3b (2003), we conducted geo-referenced videomosaickingto enhance our knowledge of the distribution of different community typesat the Håkon Mosby Mud Volcano (HMMV). This distribution is most likely linked tocertain biological and sedimentological characteristics which select for these communities.Special emphasis was put on the distribution and density of conspicuous whitemats that consisted of sulphur-oxidizing bacteria(dominant species: Beggiatoa)and ofpogonophoran worms, who rely on endosymbiotic bacteria.A vertical camera that was mounted onto the remotely operated vehicle Victor 6000generated a video flow which was processed by means of the IFREMER software MATISSE.This software facilitated the process of digital merging of images to mosaics.Navigational data including dead-reckoning and acoustic USBL positioning providedthe basis for geo-referencing of the images.As all data were geo-referenced we were able to carry out spatial analyses (GIS).This analysis allowed us to estimate the percentage coverage of different habitat typeswhich can subsequently be overlaid with other parameters defining habitat structure,e.g. bottom temperature and salinity, to accomplish a multi-disciplinary view of theHMMV and improve our understanding of this ecosystem.The mosaics obtained encompass 9% of the total edifice of the volcano increasing boththe accuracy and resolution of previous community and habitat maps. The footageshowed that bacterial mats and pogonophoran worms colonized extensive areas ofHMMV. Areas with a rough topography and small patches of sulfide oxidizing communitieswere interpreted to indicate large methane release. A provided methane releaserate can be estimated for each habitat type. The spatial analysis of the habitatdistribution that we conducted is a major step toward yielding the total discharge ofmethane through the surface of HMMV.