Primary geochemical analysis of a transect during METEOR cruise M76/1

The primary geochemical data of the transect visited during the cruise Meteor M76/1. The stations include GeoB 12802, 12803, 12808, 12811, and 12815. The geochemical data include pore-water ferrous ion, sulfate, dissolved inorganic carbon, methane, and molecular hydrogen.

Chemical and isotopic compositions of groundwaters in the Badain Jaran Desert, Northern China

Despite its extreme aridity the Badain Jaran Desert is rich in groundwater. In the southeastern part of this desert it is characterized by coexistence of high megadunes and a great number of lakes. Deuterium and oxygen 18 isotope compositions as well as hydrochemistry of groundwater, lake water, soil water and river water were investigated in detail to gain an insight into their relationships and the origin of the groundwater. The results show that the groundwater and the lake water are genetically related, but unrelated to local precipitation and the leakage of Heine River at the northern slope of the Qilian mountain. dD and d18O values of deep soil water (deeper than 40 cm) and groundwater plot on the same evaporation line E11, which shows that they have the same recharge source. The point of intersection between E11 and LMWL suggests that the groundwater originates from a water resource, which has a weighted mean value that is lighter by some 6 per mil d18O than local precipitation in Badain Jaran Desert. 3H data of water samples show that the groundwater in the Badain Jaran Desert originates from water recharged after the nuclear test. The deep fault zone underground maybe a water circulation channel based on helium analysis of groundwater. The result has guiding significance to rational exploitation and utilization of the local groundwater.

Seawater carbonate chemistry and biological processes of mussel Crassostrea gigas during experiments, 2011

Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO2-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO2 levels (partial pressure of CO2 in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated PCO2 and 15 °C hemolymph pH fell (pHe = 7.1 ± 0.2 (CO2-group) vs. 7.6 ± 0.1 (control)) and PeCO2 values in hemolymph increased (0.5 ± 0.2 kPa (CO2-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO2-incubated oysters ([HCO-3]e = 1.8 ± 0.3 mM (CO2-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pHe did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO2-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO2-incubated group. Investigation in isolated gill cells revealed a similar temperature-dependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na+/K+-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using 1H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks

Mineralogy and interstitial-water chemistry of ODP Leg 101 sites

Concentrations of dissolved Ca2+, Sr2+, Mg2+, SO4[2-], and alkalinity were measured in pore waters squeezed from sediments taken from ODP Holes 626C and 626D in the Florida Straits; Holes 627A and 627B, 628A, and 630A and 630C north of Little Bahama Bank; Holes 631 A, 632A and 632B, and 633A in Exuma Sound; and Holes 634A and 635A and 635B in Northeast Providence Channel. These data are compared with the mineralogy and strontium content of the sediments from which the waters were squeezed. Contrasts in the geochemical profiles suggest that significantly different processes govern pore-water signatures at each group of sites. In Little Bahama Bank, strong positive Ca2+ gradients are correlated with weak negative Mg2+ profiles. These trends are analogous to those seen at DSDP sites where carbonate deposits immediately overlie mafic basement, but as the depth to basement may be in excess of 5000 m, we suggest that diffusion gradients are initiated by an underlying sedimentary unit. In contrast, Ca2+ and Mg2+ gradients in Exuma Sound are not developed to any appreciable extent over similar thicknesses of sediment. We suggest that the pore-water chemistry in these deposits is principally controlled by diagenetic reactions occurring within each sequence. The location and extent of carbonate diagenesis can be estimated from dissolved Sr2+ profiles. In Little Bahama Bank and Exuma Sound, Sr2+ concentrations reach a maximum value of between 700 and 1000 µmol/L. Although the depths at which these concentrations are achieved are different for the two areas, the corresponding age of the sediment at the dissolved Sr2+ maximum is similar. Consequently, the diffusive flux of Sr2+ and the calculated rates of recrystallization in the two areas are likewise of a similar magnitude. The rates of recrystallization we calculate are lower than those found in some DSDP pelagic sites. As the waters throughout most of the holes are saturated with respect to SrSO4, celestite precipitation may cause erroneously low Sr2+ production rates and, consequently, low calculated rates of recrystallization. We therefore encourage only the discriminate use of Sr2+ profiles in the quantification of diagenetic processes.

Utility of thallium and geochemical analysis of Mariana arc sediments from ODP Hole 129-801A and 129-801B

We provide the first exploration of thallium (Tl) abundances and stable isotope compositions as potential tracers during arc lava genesis. We present a case study of lavas from the Central Island Province (CIP) of the Mariana arc, supplemented by representative sedimentary and altered oceanic crust (AOC) inputs from ODP Leg 129 Hole 801 outboard of the Mariana trench. Given the large Tl concentration contrast between the mantle and subduction inputs coupled with previously published distinctive Tl isotope signatures of sediment and AOC, the Tl isotope system has great potential to distinguish different inputs to arc lavas. Furthermore, CIP lavas have well-established inter island variability, providing excellent context for the examination of Tl as a new stable isotope tracer. In contrast to previous work (Nielsen et al., 2006b), we do not observe Tl enrichment or light epsilon 205Tl (where epsilon 205Tl is the deviation in parts per 10,000 of a sample 205Tl/203Tl ratio compared to NIST SRM 997 Tl standard) in the Jurassic-aged altered mafic ocean crust subducting outboard of the Marianas (epsilon 205Tl = - 4.4 to 0). The lack of a distinctive epsilon 205Tl signature may be related to secular changes in ocean chemistry. Sediments representative of the major lithologies from ODP Hole Leg 129 801 have 1-2 orders of magnitude of Tl enrichment compared to the CIP lavas, but do not record heavy signatures (epsilon 205Tl = - 3.0 to + 0.4), as previously found in similar sediment types (epsilon 205Tl > + 2.5; Rehkämper et al., 2004). We find a restricted range of epsilon 205Tl = - 1.8 to - 0.4 in CIP lavas, which overlaps with MORB. One lava from Guguan falls outside this range with epsilon 205Tl = + 1.2. Coupled Cs, Tl and Pb systematics of Guguan lavas suggests that this heavy Tl isotope composition may be due to preferential degassing of isotopically light Tl. In general, the low Tl concentrations and limited isotopic range in the CIP lavas is likely due to the unexpectedly narrow range of epsilon 205Tl found in Mariana subduction inputs, coupled with volcaniclastic, rather than pelagic sediment as the dominant source of Tl. Much work remains to better understand the controls on Tl processing through a subduction zone. For example, Tl could be retained in residual phengite, offering the potential exploration of Cs/Tl ratios as a slab thermometer. However, data for Tl partitioning in phengite (and other micas) is required before developing this application further. Establishing a database of Tl concentrations and stable isotopes in subduction zone lavas with different thermal parameters and sedimentary inputs is required for the future use of Tl as a subduction zone tracer.

Anaerobic oxidation of methane and sulphate reduction rates, hydrocarbons, sulphate and sulphide concentrations of sediment cores from the Larsen B embayment at the eastern site of the Antarctic Peninsula

First videographic indication of an Antarctic cold seep ecosystem was recently obtained from the collapsed Larsen B ice shelf, western Weddell Sea (Domack et al., 2005). Within the framework of the R/V Polarstern expedition ANTXXIII-8, we revisited this area for geochemical, microbiological and further videographical examinations. During two dives with ROV Cherokee (MARUM, Bremen), several bivalve shell agglomerations of the seep-associated, chemosynthetic clam Calyptogena sp. were found in the trough of the Crane and Evans glacier. The absence of living clam specimens indicates that the flux of sulphide and hence the seepage activity is diminished at present. This impression was further substantiated by our geochemical observations. Concentrations of thermogenic methane were moderately elevated with 2 µM in surface sediments of a clam patch, increasing up to 9 µM at a sediment depth of about 1 m in the bottom sections of the sediment cores. This correlated with a moderate decrease in sulphate from about 28 mM at the surface down to 23.4 mM, an increase in sulphide to up to 1.43 mM and elevated rates of the anaerobic oxidation of methane (AOM) of up to 600 pmol cm**-3 d**-1 at about 1 m below the seafloor. Molecular analyses indicate that methanotrophic archaea related to ANME-3 are the most likely candidates mediating AOM in sediments of the Larsen B seep.

Mineralogical, geochemical, and lipid biomarker study of cabonate precipitates at station GeoB9908-1

Carbonate precipitates recovered from 2,000 m water depth at the Dolgovskoy Mound (Shatsky Ridge, north eastern Black Sea) were studied using mineralogical, geochemical and lipid biomarker analyses. The carbonates differ in shape from simple pavements to cavernous structures with thick microbial mats attached to their lower side and within cavities. Low d13C values measured on carbonates (-41 to -32 per mill V-PDB) and extracted lipid biomarkers indicate that anaerobic oxidation of methane (AOM) played a crucial role in precipitating these carbonates. The internal structure of the carbonates is dominated by finely laminated coccolith ooze and homogeneous clay layers, both cemented by micritic high-magnesium calcite (HMC), and pure, botryoidal, yellowish low-magnesium calcite (LMC) grown in direct contact to microbial mats. d18O measurements suggest that the authigenic HMC precipitated in equilibrium with the Black Sea bottom water while the yellowish LMC rims have been growing in slightly 18O-depleted interstitial water. Although precipitated under significantly different environmental conditions, especially with respect to methane availability, all analysed carbonate samples show lipid patterns that are typical for ANME-1 dominated AOM consortia, in the case of the HMC samples with significant contributions of allochthonous components of marine and terrestrial origin, reflecting the hemipelagic nature of the primary sediment.

Seawater carbonate chemistry and biological processes during experiments with spider crab Hyas araneus, 2011

The combined effects of ocean warming and acidification were compared in larvae from two populations of the cold-eurythermal spider crab Hyas araneus, from one of its southernmost populations (around Helgoland, southern North Sea, 54°N, habitat temperature 3-18°C; collection: January 2008, hatch: January-February 2008) and from one of its northernmost populations (Svalbard, North Atlantic, 79°N, habitat temperature 0-6°C; collection: July 2008, hatch: February-April 2009). Larvae were exposed to temperatures of 3, 9 and 15°C combined with present-day normocapnic (380 ppm CO2) and projected future CO2 concentrations (710 and 3,000 ppm CO2). Calcium content of whole larvae was measured in freshly hatched Zoea I and after 3, 7 and 14 days during the Megalopa stage. Significant differences between Helgoland and Svalbard Megalopae were observed at all investigated temperatures and CO2 conditions. Under 380 ppm CO2, the calcium content increased with rising temperature and age of the larvae. At 3 and 9°C, Helgoland Megalopae accumulated more calcium than Svalbard Megalopae. Elevated CO2 levels, especially 3,000 ppm, caused a reduction in larval calcium contents at 3 and 9°C in both populations. This effect set in early, at 710 ppm CO2 only in Svalbard Megalopae at 9°C. Furthermore, at 3 and 9°C Megalopae from Helgoland replenished their calcium content to normocapnic levels and more rapidly than Svalbard Megalopae. However, Svalbard Megalopae displayed higher calcium contents under 3,000 ppm CO2 at 15°C. The findings of a lower capacity for calcium incorporation in crab larvae living at the cold end of their distribution range suggests that they might be more sensitive to ocean acidification than those in temperate regions.

Pore water and solid phase sulfur, carbon and iron data from samples collected in the Argentine Basin during expedition M78

Sulfur phases in the Argentine Basin.

Phosphate d18O pore-water profiles of sediment core GeoB11807-2 and GeoB11804-4

Phosphorus cycling in the ocean is influenced by biological and geochemical processes that are reflected in the oxygen isotope signature of dissolved inorganic phosphate (Pi). Extending the Pi oxygen isotope record from the water column into the seabed is difficult due to low Pi concentrations and small amounts of marine porewaters available for analysis. We obtained porewater profiles of Pi oxygen isotopes using a refined protocol based on the original micro-extraction designed by Colman (2002). This refined and customized method allows the conversion of ultra-low quantities (0.5 - 1 µmol) of porewater Pi to silver phosphate (Ag3PO4) for routine analysis by mass spectrometry. A combination of magnesium hydroxide co-precipitation with ion exchange resin treatment steps is used to remove dissolved organic matter, anions, and cations from the sample before precipitating Ag3PO4. Samples as low as 200 µg were analyzed in a continuous flow isotope ratio mass spectrometer setup. Tests with external and laboratory internal standards validated the preservation of the original phosphate oxygen isotope signature (d18OP) during micro extraction. Porewater data on d18OP has been obtained from two sediment cores of the Moroccan margin. The d18OP values are in a range of +19.49 to +27.30 per mill. We apply a simple isotope mass balance model to disentangle processes contributing to benthic P cycling and find evidence for Pi regeneration outbalancing microbial demand in the upper sediment layers. This highlights the great potential of using d18OP to study microbial processes in the subseafloor and at the sediment water interface.