ALBERT

Description: High acoustic seafloor-backscatter signals characterize hundreds of patches of methane-derived authigenic carbonates and chemosynthetic communities associated with hydrocarbon seepage on the Nile Deep Sea Fan (NDSF) in the Eastern Mediterranean Sea. During a high-resolution ship-based multibeam survey covering a ~ 225 km**2 large seafloor area in the Central Province of the NDSF we identified 163 high-backscatter patches at water depths between 1500 and 1800 m, and investigated the source, composition, turnover, flux and fate of emitted hydrocarbons. Systematic Parasound single beam echosounder surveys of the water column showed hydroacoustic anomalies (flares), indicative of gas bubble streams, above 8% of the high-backscatter patches. In echosounder records flares disappeared in the water column close to the upper limit of the gas hydrate stability zone located at about 1350 m water depth due to decomposition of gas hydrate skins and subsequent gas dissolution. Visual inspection of three high-backscatter patches demonstrated that sediment cementation has led to the formation of continuous flat pavements of authigenic carbonates typically 100 to 300 m in diameter. Volume estimates, considering results from high-resolution autonomous underwater vehicle (AUV)-based multibeam mapping, were used to calculate the amount of carbonate-bound carbon stored in these slabs. Additionally, the flux of methane bubbles emitted at one high-backscatter patch was estimated (0.23 to 2.3 × 10**6 mol a**-1) by combined AUV flare mapping with visual observations by remotely operated vehicle (ROV). Another high-backscatter patch characterized by single carbonate pieces, which were widely distributed and interspaced with sediments inhabited by thiotrophic, chemosynthetic organisms, was investigated using in situ measurements with a benthic chamber and ex situ sediment core incubation and allowed for estimates of the methane consumption (0.1 to 1 × 10**6 mol a**-1) and dissolved methane flux (2 to 48 × 10**6 mol a**-1). Our comparison of dissolved and gaseous methane fluxes as well as methane-derived carbonate reservoirs demonstrates the need for quantitative assessment of these different methane escape routes and their interaction with the geo-, bio-, and hydrosphere at cold seeps.

Description: Bathymetry based on data recorded during M111 between 10.10.2014 and 01.11.2014 in the eastern Mediterranean Sea. The aim of the cruise was to quantify the deep geometry and architecture of the Calabria subduction zone and Ionian Sea lithosphere and to shed light on the nature of the Ionian Sea with OBS/OBH and deep sea seismics. Additionally the M111 cruise formed the core of an ambitious investigation covering the Ionian Sea and island of Sicily. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry. Description of processed data sources: During the cruise M111 the Kongsberg EM122 multibeam echosounder with a nominal sounding frequency of 12 kHz was utilized. 288 beams (and up to 864 soundings in equidistant and dual swath mode) are formed for each ping with a 1°(Tx)/2°(Rx) footprint while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult https://www.km.kongsberg.com/. The EM122 was recording during the deployment of the OBH/OBS, during seismic surveys and during transits. Responsible person during this cruise / PI: Ingo Klaucke (iklaucke@geomar.de). Description of data processing: Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-System suite (Caress, D.W., and D.N. Chayes, MB-System Version 5.5, open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. A tide correction was applied, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. The CTD measurements taken during the M111 cruise were sufficient to represent the changes in the sound velocity throughout the study area. Further roll, pitch and heave corrections were not applied for the M111 data. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. The currently published bathymetric grid of the cruise has a resolution of 70 m. A higher resolution is, at least partly, achievable. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd-grid contains the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de). Chief Scientist: H. Kopp hkopp@geomar.de CR: https://www.tib.eu/de/suchen/id/awi%3Adoi~10.2312%252Fcr_m111/ CSR: http://www.bsh.de/aktdat/dod/fahrtergebnis/2014/20140277.htm A special thanks goes to the PIs and watch keeper of the hydroacoustic systems during M111: Marzia Rovere, Ingo Klaucke, Anne Krabbenhoeft, Marc-André Gutscher

Description: Bathymetry data based on data recorded during M112 between 06.11.2014 and 15.12.2014 and during POS499 between 04.05.2016 and 22.05.2016 in the Mediterranean Sea. The aim of the cruises was to investigate in mud volcanoes of the Calabrian Arc in Italian waters, where 54 potential mud volcanoes have been documented while it remained unclear whether they are still active or not. Therefore, the bathymetric surveys were accompanied with investigations in the water column. Several sound velocity profiles (SVPs) were taken to correct the bathymetry. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de ) as responsible party for bathymetry post-processing and its products. Description of processed data sources at M112: During the cruise M112 the Kongsberg EM122 multibeam echosounder with a nominal sounding frequency of 12 kHz was utilized. 288 beams (and up to 864 soundings in equidistant and dual swath mode) are formed for each ping with a 1°(Tx)/2°(Rx) footprint while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult https://www.km.kongsberg.com/. The EM122 was recording constantly within the permitted areas, either designated to bathymetry surveys or flare imaging-surveys. Responsible person during this cruise / PI: Paul Wintersteller (pwintersteller@marum.de ) and Christian Ferreira (cferreira@marum.de ). Description of processed data sources during POS499: During the RV POSEIDON cruise POS499 the ELAC SB3050 multibeam echo sounder with a nominal sounding frequency of 50 kHz was utilized. 384 beams are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult http://www.mdsys.co.kr/down/ELAC/SB_3050.pdf. During the POS499 cruise the swath - width has been set to AUTO mode and was commonly observed at around 80°. This given swath ‐ width refers to a coverage of about 1.6 times the water ‐depth and reduces the max. number of beams collected per ping to less than 240. Most of the time the multi‐ping mode has been used with a receiver reception gain value of 45dB. The recorded bathymetry covers in total 880 km and the mapped area is based on the bathymetry results from the M111 & M112 cruises. Responsible person for hydroacoustics during this cruise / PI: Paul Wintersteller (pwintersteller@marum.de ) Description of data processing : Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM/FB5, responsible person: Paul Wintersteller (seafloor-imaging@marum.de ). The open source software MB-system suite (Caress, D.W., and D.N. Chayes, MB-System Version 5, Open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. A tide correction was applied, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. Tidal changes in the Mediterranean Sea are up to max. 1m. CTD measurements were taken during the M112 and POS499 cruise, and these were sufficient to represent the changes in the sound velocity throughout the study area. Further pitch and heave corrections were not applied for the M112 and POS499 data though a roll off-set of -0.46° was applied for the POS499 data (mbset). Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid. The currently published merged bathymetric grids of the cruise have a resolution of 30 m. A higher resolution is, at least partly, achievable. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid contains the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).

Description: Bathymetry data based on Multibeam echosounder SB3050 (MBES) was recorded during RV POSEIDON cruise POS462 between 28.10.2013 and 21.11.2013 in the Eastern Mediterranean Sea. The prime objective of the cruise was the investigation of the 'Anaximander Mountains' south of Turkey and therefore to decipher key processes of mud volcanoes, which led to the emission of gas hydrates in shallow marine sediments. During 8 AUV and several MBES surveys, four mud volcanoes were mapped. The detailed mapping of these mud volcanoes and identification of gas hydrate emissions were the main research interests of the hydroacoustic group on board. Additionally samples of the mud volcanoes were taken using a gravity corer and heat/flow measurements were done. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the RV POSEIDON cruise POS462 the ship-mounted ELAC SB3050 multibeam echosounder with a nominal sounding frequency of 50 kHz was utilized. A maximum of 384 beams with a 1.5°(TX)/2°(RX) footprint are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult http://www.mdsys.co.kr/down/ELAC/SB_3050.pdf. A maximum range of 2000 was achieved, which caused limitations of the mapped area. Due to static beam positions and angles of the ELAC system the number of beams was reduced according to the depth. In shallower parts a maximum of 160/180 beams were produced. In comparison, in deeper parts (1800/2000m), these numbers were reduced by 40 beams. The Hydrostar software by ELAC was used to gather data. Problems with the navigation sensor and motion sensor CODA F180 were reported (further information can be found in the cruise report). Responsible person for hydroacoustic during this cruise / PI: Christian dos Santos Ferreira (cferrei-ra@marum.de) Chief Scientist: Gerhard Bohrmann (gbohrmann@marum.de) CR: http://elib.suub.uni-bremen.de/edocs/00103551-1.pdf CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2013/20130095.htm A special thanks goes to the watchkeeper: Ammar Aljuhne

Description: Bathymetry data based on Multibeam echosounder SB3050 (MBES) was recorded during RV POSEIDON cruise POS462 between 28.10.2013 and 21.11.2013 in the Eastern Mediterranean Sea. The prime objective of the cruise was the investigation of the 'Anaximander Mountains' south of Turkey and therefore to decipher key processes of mud volcanoes, which led to the emission of gas hydrates in shallow marine sediments. During 8 AUV and several MBES surveys, four mud volcanoes were mapped. The detailed mapping of these mud volcanoes and identification of gas hydrate emissions were the main research interests of the hydroacoustic group on board. Additionally samples of the mud volcanoes were taken using a gravity corer and heat/flow measurements were done. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the RV POSEIDON cruise POS460 the ship-mounted ELAC SB3050 multibeam echosounder with a nominal sounding frequency of 50 kHz was utilized. A maximum of 384 beams with a 1.5°(TX)/2°(RX) footprint are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult http://www.mdsys.co.kr/down/ELAC/SB_3050.pdf. A maximum range of 2000 was achieved, which caused limitations of the mapped area. Due to static beam positions and angles of the ELAC system the number of beams was reduced according to the depth. In shallower parts a maximum of 160/180 beams were produced. In comparison, in deeper parts (1800/2000m), these numbers were reduced by 40 beams. The Hydrostar software by ELAC was used to gather data. Problems with the navigation sensor and motion sensor CODA F180 were reported (further information can be found in the cruise report). Responsible person for hydroacoustic during this cruise / PI: Christian dos Santos Ferreira (cferreira@marum.de) Description of data processing: Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM/FB5, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-system suite (Caress, D.W., and D.N. Chayes, MB-System Version 5.4., Open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. No tide correction was applied. Five CTD measurements were taken during the POS462 cruise, and these were sufficient to represent the changes in the sound velocity throughout the study area. Further pitch and heave corrections were not applied for the POS462 data though a roll off-set of 1.5° was applied (mbset). Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. The currently published bathymetric grid of the cruise has a resolution of 30 m. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid contains the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de). Chief Scientist: Gerhard Bohrmann (gbohrmann@marum.de) CR: http://elib.suub.uni-bremen.de/edocs/00103551-1.pdf CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2013/20130095.htm Bathymetric raw-dataset published: not yet A special thanks goes to the watchkeeper: Ammar Aljuhne, Miriam Römer

Description: Bathymetry based on data recorded during POS317-4 between 16.10.2004 and 04.11.2004. This cruise focused on methane seeps off Georgia and Turkey. Different geological settings were studied by using pressurized sampling techniques and remotely operated vehicles (ROVs).

Description: The Menez Gwen hydrothermal vents, located on the flanks of a small young volcanic structure in the axial valley of the Menez Gwen seamount, are the shallowest known vent systems on the Mid-Atlantic Ridge that host chemosynthetic communities. Although visited several times by research cruises, very few images have been published of the active sites, and their spatial dimensions and morphologies remain difficult to comprehend. We visited the vents on the eastern flank of the small Menez Gwen volcano during cruises with RV Poseidon (POS402, 2010) and RV Meteor (M82/3, 2010), and used new bathymetry and imagery data to provide first detailed information on the extents, surface morphologies, spatial patterns of the hydrothermal discharge and the distribution of dominant megafauna of five active sites. The investigated sites were mostly covered by soft sediments and abundant white precipitates, and bordered by basaltic pillows. The hydrothermally-influenced areas of the sites ranged from 59 to 200 m**2. Geo-referenced photomosaics and video data revealed that the symbiotic mussel Bathymodiolus azoricus was the dominant species and present at all sites. Using literature data on average body sizes and biomasses of Menez Gwen B. azoricus, we estimated that the B. azoricus populations inhabiting the eastern flank sites of the small volcano range between 28,640 and 50,120 individuals with a total biomass of 50 to 380 kg wet weight. Based on modeled rates of chemical consumption by the symbionts, the annual methane and sulfide consumption by B. azoricus could reach 1760 mol CH4 yr**-1 and 11,060 mol H2S yr**-1. We propose that the chemical consumption by B. azoricus over at the Menez Gwen sites is low compared to the natural release of methane and sulfide via venting fluids.

Description: Between 01.10.2003 and 12.11.2003, bathymetric data was acquired in the Gulf of Mexico during the R/V SONNE cruise SO174. The expedition was dedicated to the types and structures of near-surface marine methane hydrates and the environmental conditions required for their formation. Furthermore, the cruise aimed at the assessment of microbiological turnover and deployments of long-term observatories for examination of the mechanisms controlling the formation and dissociation of gas hydrate. Bathymetric mapping with the multibeam echosounder (MBES) SIMRAD EM120 was utilized to conduct high-quality seafloor maps in water depths between 500 and 1000 m, covering an area of 350 km² and notably improving the resolution of existing bathymetry. Sub-bottom profiling and plume imaging, visual seafloor observation, lander deployments, sediment coring, CT scanning and biological sampling complemented the research programme. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the SO174 cruise, the hull-mounted multibeam echosounder (MBES) SIMRAD EM120 was utilized to perform bathymetric mapping. It allows to conduct surveys in water depths of up to 11,000 m. Two transducer arrays transmit frequency coded acoustic signals (11.25 to 12.6 kHz). Data acquisition is based on successive emission-reception cycles of the signal. While the emission beam has a dimension of 150° across and 2° along track, the reception is obtained from 191 overlapping beams with widths of 2° across and 20° along track. The beam footprint has a dimension of 2° by 2°. The beam spacing can be set to equidistant or equiangular. For further information on the system, consult: https://www.km.kongsberg.com/ Depth is estimated from each beam by using the two-way travel time and the beam angle known from each beam, and taking into account the ray bending due to refraction in the water column by sound speed variations. Combining phase and amplitude is used to provide measurement accuracy practically independent of the beam pointing angle. A sound velocity for the calibration of the SIMRAD EM120 profile was obtained through a CTD cast. Responsible person during this cruise / PI: Gerhard Bohrmann (gbohrmann@marum.de) & Florian Meier (florian.meier@iwes.fraunhofer.de) Description of data processing: Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM/FB5, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-System suite (Caress, D.W., and D.N. Chayes, MB-System Version 5.5, open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. The data was corrected for tide. There were no roll, pitch and heave corrections. Using Mbeditviz, artefacts were cleaned manually. NetCDF (GMT) grids of the edited data as well as statistics were created with mbgrid. The published bathymetric grid of the EM120 during cruise SO174 has a resolution of 35 m. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. A higher resolution is, at least partly, achievable. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid contains the standard deviation for each cell. All grids produced are retrievable through the PANGAEA database (www.pangaea.de). Chief Scientist: Gerhard Bohrmann (gbohrmann@marum.de) CR: http://oceanrep.geomar.de/13539/1/GEOMAR_Rep_117_SO174.pdf CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2003/20040025.htm Raw data: https://doi.pangaea.de/10.1594/PANGAEA.902452

Description: We mapped, sampled, and quantified gas emissions at the continental margin west of Svalbard during R/V Heincke cruise He-387 in late summer 2012. Hydroacoustic mapping revealed that gas emissions were not limited to a zone just above 396 m below sea level (m b.s.l.). Flares from this depth gained significant attention in the scientific community in recent years because they may be caused by bottom water-warming induced hydrate dissolution in the course of global warming and/or by recurring seasonal hydrate formation and decay. We found that gas emissions occurred widespread between about 80 and 415 m b.s.l. which indicates that hydrate dissolution might only be one of several triggers for active hydrocarbon seepage in that area. Gas emissions were remarkably intensive at the main ridge of the forlandet moraine complex in 80 to 90 m water depths, and may be related to thawing permafrost. Focused seafloor investigations were performed with the remotely operated vehicle (ROV) "Cherokee". Geochemical analyses of gas bubbles sampled at about 240 m b.s.l. as well as at the 396 m gas emission sites revealed that the vent gas is primarily composed of methane (〉 99.70%) of microbial origin (average d13C = -55.7 per mil V-PDB). Estimates of the regional gas bubble flux from the seafloor to the water column in the area of possible hydrate decomposition were achieved by combining flare mapping using multibeam and single beam echosounder data, bubble stream mapping using a ROV-mounted horizontally-looking sonar, and quantification of individual bubble streams using ROV imagery and bubble counting. We estimated that about 53 × 10**6 mol methane were annually emitted at the two areas and allow a large range of uncertainty due to our method (9 to 118 × 10**6 mol yr**-1). These amounts, first, show that gas emissions at the continental margin west of Svalbard were in the same order of magnitude as bubble emissions at other geological settings, and second, may be used to calibrate models predicting hydrate dissolution at present and in the future, third, may serve as baseline (year 2012) estimate of the bubble flux that will potentially increase in future due to ever-increasing global-warming induced bottom water-warming and hydrate dissolution.