(Supplementary Table 1) Proportions of methane (C1) to ethane (C2) and the stable isotope composition of methane (d13CCH4) of gas and oil collected by gas bubble sampler during cruise M 114 in the southern Gulf of Mexico

Hydrocarbon seepage is a widespread process at the continental margins of the Gulf of Mexico. We used a multidisciplinary approach, including multibeam mapping and visual seafloor observations with different underwater vehicles to study the extent and character of complex hydrocarbon seepage in the Bay of Campeche, southern Gulf of Mexico. Our observations showed that seafloor asphalt deposits previously only known from the Chapopote Knoll also occur at numerous other knolls and ridges in water depths from 1230 to 3150 m. In particular the deeper sites (Chapopopte and Mictlan knolls) were characterized by asphalt deposits accompanied by extrusion of liquid oil in form of whips or sheets, and in some places (Tsanyao Yang, Mictlan, and Chapopote knolls) by gas emission and the presence of gas hydrates in addition. Molecular and stable carbon isotopic compositions of gaseous hydrocarbons suggest their primarily thermogenic origin. Relatively fresh asphalt structures were settled by chemosynthetic communities including bacterial mats and vestimentiferan tube worms, whereas older flows appeared largely inert and devoid of corals and anemones at the deep sites. The gas hydrates at Tsanyao Yang and Mictlan Knolls were covered by a 5-to-10 cm-thick reaction zone composed of authigenic carbonates, detritus, and microbial mats, and were densely colonized by 1-2 m-long tube worms, bivalves, snails, and shrimps. This study increased knowledge on the occurrences and dimensions of asphalt fields and associated gas hydrates at the Campeche Knolls. The extent of all discovered seepage structure areas indicates that emission of complex hydrocarbons is a widespread, thus important feature of the southern Gulf of Mexico.

Biogeochemical investigation of microbial mats from the hypoxic region of the Crimean Shelf (Black Sea)

Biogeochemical measurements in sediment cores collected with the submersible JAGO (pusch cores) and a TV-MUC in the Black Sea during MSM15/1, Northwest Crimea (HYPOX Project), at water depths between 152-156 m. A series of microbial mats were sampled on the hypoxic region of the Crimean Shelf. Concentrations of organic carbon (Corg) and nitrogen (N) were measured on finely powdered, freeze-dried subsamples of sediment using a using a Fisons NA-1500 elemental analyzer. For organic carbon determination samples were pre-treated with 12.5% HCl to remove carbonates. Chlorophyll a (chl a), phaeopigments (PHAEO) and chloroplastic pigment equivalents (CPE) was measured according to Schubert et al., (2005) and total hydrolyzable amino acids (THAA) and single amino acid: ASP, GLU, SER, HIS, GLY, THR, ARG, ALA, TYR, MET, VAL, PHE, ILE, LEU, LYS following Dauwe et al., 1998. High-resolution ex situ sulfide and pH microprofiles, were assessed only for station MSM15/1_492_PUC1. "in mat 1, 2 and 3" refers to 3 different profiles in 3 different spots of the microbial mat, whereas "outside mat", a profile outside the microbial mat.

Biogeochemical measurements of sediments collected at station MSM15/1_492-PUC1 (microbial mat 1) in the Black Sea during the MSM15/1 cruise in 2010

Biogeochemical measurements in sediment cores collected with the submersible JAGO (pusch cores) and a TV-MUC in the Black Sea during MSM15/1, Northwest Crimea (HYPOX Project), at water depths between 152-156 m. A series of microbial mats were sampled on the hypoxic region of the Crimean Shelf. Concentrations of organic carbon (Corg) and nitrogen (N) were measured on finely powdered, freeze-dried subsamples of sediment using a using a Fisons NA-1500 elemental analyzer. For organic carbon determination samples were pre-treated with 12.5% HCl to remove carbonates. Chlorophyll a (chl a), phaeopigments (PHAEO) and chloroplastic pigment equivalents (CPE) was measured according to Schubert et al., (2005) and total hydrolyzable amino acids (THAA) and single amino acid: ASP, GLU, SER, HIS, GLY, THR, ARG, ALA, TYR, MET, VAL, PHE, ILE, LEU, LYS following Dauwe et al., 1998.

Biogeochemical measurements of sediments collected at station MSM15/1_492-PUC6 (reference site 3) in the Black Sea during the MSM15/1 cruise in 2010

Biogeochemical measurements in sediment cores collected with the submersible JAGO (pusch cores) and a TV-MUC in the Black Sea during MSM15/1, Northwest Crimea (HYPOX Project), at water depths between 152-156 m. A series of microbial mats were sampled on the hypoxic region of the Crimean Shelf. Concentrations of organic carbon (Corg) and nitrogen (N) were measured on finely powdered, freeze-dried subsamples of sediment using a using a Fisons NA-1500 elemental analyzer. For organic carbon determination samples were pre-treated with 12.5% HCl to remove carbonates. Chlorophyll a (chl a), phaeopigments (PHAEO) and chloroplastic pigment equivalents (CPE) was measured according to Schubert et al., (2005) and total hydrolyzable amino acids (THAA) and single amino acid: ASP, GLU, SER, HIS, GLY, THR, ARG, ALA, TYR, MET, VAL, PHE, ILE, LEU, LYS following Dauwe et al., 1998.

Sea-floor videos and photographs (benthos) along 6 shelf profiles from the eastern Weddell Sea, Antarctica taken with remote operated vehicel CHEROKEE during Polarstern cruise ANT-XXI/2

The ROV operations had three objectives: (1) to check, whether the "Cherokee" system is suited for advanced benthological work in the high latitude Antarctic shelf areas; (2) to support the disturbance experiment, providing immediate visual Information; (3) to continue ecological work that started in 1989 at the hilltop situated at the northern margin of the Norsel Bank off the 4-Seasons Inlet (Weddell Sea). The "Cherokee" is was equipped with 3 video cameras, 2 of which support the operation. A high resolution Tritech Typhoon camera is used for scientific observations to be recorded. In addition, the ROV has a manipulator, a still camera, lights and strobe, compass, 2 lasers, a Posidonia transponder and an obstacle avoidance Sonar. The size of the vehicle is 160 X 90 X 90cm. In the present configuration without TMS (tether management system) the deployment has to start with paying out the full cable length, lay it in loops on deck and connect the glass fibres at the tether's spool winch. After a final technical check the vehicle is deployed into the water, actively driven perpendicular to the ship's axis and floatings are fixed to the tether. At a cable length of approx. 50 m, the tether is tightened to the depressor by several cable ties and both components are lowered towards the sea floor, the vehicle by the thruster's propulsion and the depressor by the ship's winch. At 5 m intervals the tether has to be tied to the single conductor cable. In good weather conditions the instruments supporting the navigation of the ROV, especially the Posidonia system, allow an operation mode to follow the ship's course if the ship's speed is slow. Together with the lasers which act as a scale in the images they also allow a reproducible scientific analysis since the transect can be plotted in a GIS system. Consequently, the area observed can be easily calculated. An operation as a predominantly drifting system, especially in areas with bottom near currents, is also possible, however, the connection of the tether at the rear of the vehicle is unsuitable for such conditions. The recovery of the system corresponds to that of the deployment. Most important is to reach the surface of the sea at a safe distance perpendicular to the ship's axis in order not to interfere with the ship's propellers. During this phase the Posidonia transponder system is of high relevance although it has to be switched off at a water depth of approx. 40 m. The minimum personal needed is 4 persons to handle the tether on deck, one person to operate the ship's winch, one pilot and one additional technician for the ROV's operation itself, one scientist, and one person on the ship's bridge in addition to one on deck for whale watching when the Posidonia system is in use. The time for the deployment of the ROV until it reaches the sea floor depends on the water depth and consequently on the length of the cable to be paid out beforehand and to be tightened to the single conductor cable. Deployment and recovery at intermediate water depths can last up to 2 hours each. A reasonable time for benthological observations close to the sea floor is 1 to 3 hours but can be extended if scientifically justified. Preliminary results: after a first test station, the ROV was deployed 3 times for observations related to the disturbance experiment. A first attempt to Cross the hilltop at the northern margin of the Norsel Bank close to the 4- Seasons Inlet was successful only for the first hundreds of metres transect length. The benthic community was dominated in biomass by the demosponge Cinachyra barbata. Due to the strong current of approx. 1 nm/h, the design of the system, and an expected more difficult current regime between grounded icebergs and the top of the hilltop the operation was stopped before the hilltop was reached. In a second attempt the hilltop was successfully crossed because the current and wind situation was much more suitable. In contrast to earlier expeditions with the "sprint" ROV it was the first time that both slopes, the smoother in the northeast and the steeper in the southwest were continuously observed during one cast. A coarse classification of the hilltop fauna shows patches dominated by single taxa: cnidarians, hydrozoans, holothurians, sea urchins and stalked sponges. Approximately 20 % of the north-eastern slope was devastated by grounding icebergs. Here the sediments consisted of large boulders, gravel or blocks of finer sediment looking like an irregularly ploughed field. On the Norsel Bank the Cinachyra concentrations were locally associated with high abundances of sea anemones. Total observation time amounted to 11.5 hours corresponding to almost 6-9 km transect length.