ALBERT

Description: Pore water and solid phase concentration in samples collected during RV Heincke expeditions HE406, HE443 and, HE461

Description: The Guaymas Basin hydrothermal vents in the Gulf of California have been visited during RV Atlantis mission AT37-06 in December 2016. Aim of this mission was to understand element fluxes and microbially driven reactions at the diffusive vent sites. The submarine ALVIN and push cores were used to sample undisturbed sediments at specific locations covering different temperature and geochemical regimes. From these cores porewater was sampled using Rhizons. Here we present concentrations of select anions in the porewater. We measured the concentrations of sulfate, sulfide, chloride, ammonia, phosphate and silicate.

Description: The Guaymas Basin hydrothermal vents in the Gulf of California (Mexico) were visited with the research vessel RV Atlantis in November to December 2018 (mission AT 42-05). Due to its proximity to land, this area is covered with thick organic-rich sediments. In the subsurface heated fluids enrich in hydrocarbons gases, leading to complex biogeochemical reactions in surface sediments (Teske et al., 2016; doi:10.3389/fmicb.2016.00075). We used the submarine ALVIN to collect sediments with push cores at sites covered with different mat types and surrounding areas. Aim of this effort was to describe the biogeochemistry and the fluxes of dissolved species in these sediments. We collected porewater from these push cores using Rhizon technology (Seeberg-Elverfeldt et al., 2005; doi:10.4319/lom.2005.3.361). Porewater sampling was performed in anoxic tents to preserve oxygen-sensitive dissolved metal species. Samples were preserved according to established protocols. In the home laboratory we measured concentrations of dissolved inorganic carbon, chloride, sulfate, sulfide, dissolved inorganic carbon, nitrate, nitrite, ammonium, phosphate and silicate and concentrations of dissolved iron using two approaches and manganese were assessed. Sediment cores is the direct vicinity of these cores were taken as replicates for the measurement of dissolved gases. Cores were sectioned and 2 ml sediments were sampled into glass-vials filled with 5 ml sodium hydroxide solutions and were sealed gas-tight. Concentrations of the hydrocarbon gases methane, ethane, propane, i-butane and butane were measured using gas chromatography coupled to flame ionization detection.

Description: Here we measured the concentrations and carbon isotopic composition of methane and ethane in sediment cores from several gas-rich sites in the Gulf of Cadiz. The aim of this sampling was to reveal the fate of both gases within the sediment in relation to the consumption of sulfate (Anaerobic oxidation of methane) and to measure isotope effects of this process on the carbon isotopic compositions. Therefore, sediment samples were collected during Meteor expedition M167 in October 2020 by gravity coring. After recovery, the core was cut into 1 m sections that were vertically split into an archive and a working half. Directly after this, defined volumes of 2 ml sediment were samples with cut-off syringes and transferred into 20 ml vials filled with 5 ml NaOH (1M) solution. Vials were immediately sealed with butyl septa and crimps. Methane and ethane concentrations were measured by gas chromatography coupled to flame ionization detection. Carbon isotopic composition of methane and ethane were measured as isotopomers of CO2 produced from these gases by in-line combustion coupled to isotope ratio mass spectrometry. Both methane and ethane were consumed with the consumption of methane. Methane isotopic composition was strongly altered in these zones. By contrast, isotope values of ethane remained rather stable.

Description: An experiment was conceived in which we monitored degradation of GlcDGD. Independent of the fate of the [14C]glucosyl headgroup after hydrolysis from the glycerol backbone, the 14C enters the aqueous or gas phase whereas the intact lipid is insoluble and remains in the sediment phase. Total degradation of GlcDGD then is obtained by combining the increase of radioactivity in the aqueous and gaseous phases. We chose two different sediment to perform this experiment. One is from microbially actie surface sediment sampled in February 2010 from the upper tidal flat of the German Wadden Sea near Wremen (53° 38' 0N, 8° 29' 30E). The other one is deep subsurface sediments recovered from northern Cascadia Margin during Integrated Ocean Drilling Program Expedition 311 [site U1326, 138.2 meters below seafloor (mbsf), in situ temperature 20 °C, water depth 1,828 m. We performed both alive and killed control experiments for comparison. Surface and subsurface sediment slurry were incubated in the dark at in situ temperature, 4 °C and 20 °C for 300 d, respectively. The sterilized slurry was stored at 20 °C. All incubations were carried out under N2 headspace to ensure anaerobic conditions. The sampling frequency was high during the first half-month, i.e., after 1, 2, 7, and 14 d; thereafter, the sediment slurry was sampled every 2 months. At each time point, samples were taken in triplicate for radioactivity measurements. After 300 d of incubation, no significant changes of radioactivity in the aqueous phase were detected. This may be the result of either the rapid turnover of released [14C] glucose or the relatively high limit of detection caused by the slight solubility (equivalent to 2% of initial radioactivity) of GlcDGD in water. Therefore, total degradation of GlcDGD in the dataset was calculated by combining radioactivity of DIC, CH4, and CO2, leading to a minimum estimate.