Chemistry of sediment profile GeoB4906

Mineralization of organic matter and the subsequent dissolution of calcite were simulated for surface sediments of the upper continental slope off Gabon by using microsensors to measure O2, pH, pCO2 and Ca2+ (in situ), pore-water concentration profiles of NO3-, NH4+, Fe2+, and Mn2+ and SO42- (ex situ), as well as sulfate reduction rates derived from incubation experiments. The transport and reaction model CoTReM was used to simulate the degradation of organic matter by O2, [NO3]-, Fe(OH)3 and [SO4]2-, reoxidation reactions involving Fe2+ and Mn2+, and precipitation of FeS. Model application revealed an overall rate of organic matter mineralization amounting to 50 µmol C cm**-2 yr**-1, of which 77% were due to O2, 17% to [NO3]- and 3% to Fe(OH)3 and 3% to [SO4]2-. The best fit for the pH profile was achieved by adapting three different dissolution rate constants of calcite ranging between 0.01 and 0.5% d-1 and accounting for different calcite phases in the sediment. A reaction order of 4.5 was assumed in the kinetic rate law. A CaCO3 flux to the sediment was estimated to occur at a rate of 42 g m**-2 yr**-1 in the area of equatorial upwelling. The model predicts a redissolution flux of calcite amounting to 36 g m**-2 yr**-1, thus indicating that ~90% of the calcite flux to the sediment is redissolved.

Geochemical studies of surface sediment samples off North-West Africa

One hundred and twenty-eight surface-sediment samples collected off North-West Africa were studied geochemically to detect the expressions of different meridional climate regimes and zonal productivity gradients in the surface sediments. This geochemical multi-tracer approach, coupled with additional information on the bulk carbonate and TOC contents makes it possible to characterise the sedimentological regime in detail. Typical terrigenous elements like Al, K and Fe mirror the importance of the humid (fluvial) influence in the north of the study area and the dominance of aeolian input in the south. Furthermore, the distributions of Ti and Fe in the surface sediments serve as tracers for the supply of eolian volcanic material from the Canary Islands. The spatial variability of the TOC contents in the surface sediments closely follows the ocean surface productivity patterns, whereas the CaCO3 contents are mainly controlled by dilution with terrigenous matter. The potential productivity proxy Ba is not a reliable tracer for productivity in this region, since it is mainly supplied by terrigenous input (coupled with aluminosilicates).

Physical oceanography during Maria S. Merian cruise MSM21/2

Flemish Pass, located at the western subpolar margin, is a passage (sill depth 1200 m) that is constrained by the Grand Banks and the underwater plateau Flemish Cap. In addition to the Deep Western Boundary Current (DWBC) pathway offshore of Flemish Cap, Flemish Pass represents another southward transport pathway for two modes of Labrador Sea Water (LSW), the lightest component of North Atlantic Deep Water carried with the DWBC. This pathway avoids potential stirring regions east of Flemish Cap and deflection into the interior North Atlantic. Ship-based velocity measurements between 2009 and 2013 at 47°N in Flemish Pass and in the DWBC east of Flemish Cap revealed a considerable southward transport of Upper LSW through Flemish Pass (15-27%, -1.0 to -1.5 Sv). About 98% of the denser Deep LSW were carried around Flemish Cap as Flemish Pass is too shallow for considerable transport of Deep LSW. Hydrographic time series from ship-based measurements show a significant warming of 0.3°C/decade and a salinification of 0.03/decade of the Upper LSW in Flemish Pass between 1993 and 2013. Almost identical trends were found for the evolution in the Labrador Sea and in the DWBC east of Flemish Cap. This indicates that the long-term hydrographic variability of Upper LSW in Flemish Pass as well as in the DWBC at 47°N is dominated by changes in the Labrador Sea, which are advected southward. Fifty years of numerical ocean model simulations in Flemish Pass suggest that these trends are part of a multidecadal cycle.

(Table S2) Cell concentrations of individual and combined Alexandrium spp. and phylogenetic groups as obtained by qPCR assay and Utermöhl counts, as well as particulate PSP toxin concentrations from discrete water depths

Molecular methods provide promising tools for routine detection and quantification of toxic microalgae in plankton samples. To this end, novel TaqMan minor groove binding probes and primers targeting the small (SSU) or large (LSU) ribosomal subunit (rRNA) were developed for two species of the marine dinoflagellate genus Alexandrium (A. minutum, A. tamutum) and for three groups/ribotypes of the A. tamarense species complex: Group I/North American (NA), Group II/Mediterranean (ME) and Group III/Western European (WE). Primers and probes for real-time quantitative PCR (qPCR) were species-specific and highly efficient when tested in qPCR assays for cross-validation with pure DNA from cultured Alexandrium strains. Suitability of the qPCR assays as molecular tools for the detection and estimation of relative cell abundances of Alexandrium species and groups was evaluated from samples of natural plankton assemblages along the Scottish east coast. The results were compared with inverted microscope cell counts (Utermöhl technique) of Alexandrium spp. and associated paralytic shellfish poisoning (PSP) toxin concentrations. The qPCR assays indicated that A. tamarense (Group I) and A. tamutum were the most abundant Alexandrium taxa and both were highly positively correlated with PSP toxin content of plankton samples. Cells of A. tamarense (Group III) were present at nearly all stations but in low abundance. Alexandrium minutum and A. tamarense (Group II) cells were not detected in any of the samples, thereby arguing for their absence from the specific North Sea region, at least at the time of the survey. The sympatric occurrence of A. tamarense Group I and Group III gives further support to the hypothesis that the groups/ribotypes of the A. tamarense species complex are cryptic species rather than variants belonging to the same species.

High resolution bathymetric compilation for Potter Cove, WAP, Antarctica, with links to data in ArcGIS format

The bathymetry raster with a resolution of 5 m x 5 m was processed from unpublished single beam data from the Argentine Antarctica Institute (IAA, 2010) and multibeam data from the United Kingdom Hydrographic Office (UKHO, 2012) with a cell size of 5 m x 5 m. A coastline digitized from a satellite image (DigitalGlobe, 2014) supplemented the interpolation process. The 'Topo to Raster' tool in ArcMap 10.3 was used to merge the three data sets, while the coastline represented the 0-m-contour to the interpolation process ('contour type option').

Experiment: Growth rates and percentages of normal versus malformed versus incomplete versus incomplete and malformed coccoliths

The coccolithophore Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was cultured in natural seawater with the addition of either the microtubule-inhibitor colchicine, the actin-inhibitor cytochalasin B, or the photosynthesis inhibitor 3-(3,4 dichlorophenyl)-1,1-dimethyl-urea (DCMU). Additionally, E. huxleyi was cultured at different light intensities and temperatures. Growth rate was monitored, and coccolith morphology analyzed. While every treatment affected growth rate, the percentage of malformed coccoliths increased with colchicine, cytochalasin B, and at higher than optimal temperature. These results represent the first experimental evidence for the role of microtubules and actin microfilaments in coccolith morphogenesis.

Micropaleontological investigation of Late Albanian Col de Palluel

The Niveau Breistroffer black shale succession in the Vocontian Basin (SE France) is the regional equivalent of the widely distributed Late Albian Oceanic Anoxic Event 1d. The studied black shale-rich interval at the Col de Palluel section is 6.28 m thick and comprises four black shale units with up to 2.5 wt% total organic carbon (TOC) intercalated with marlstones. Calcareous nannofossil, palynomorph, planktic Foraminifera and stable isotopic data from the Niveau Breistroffer succession suggest that short-term climate changes influenced its deposition, with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition. An increase in the terrigenous/marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation. A nutrient index based on calcareous nannofossils and the abundance pattern of small (63-125 µm) hedbergellid Foraminifera show short-term changes in the productivity of the surface water. Surface-water productivity was reduced during black shale formation and increased during marlstone deposition. A calcareous nannofossil temperature index and bulk-rock oxygen isotope data indicate relative temperature changes, with warmer surface waters for black shale samples. At these times, warm-humid climate and reduced surface-water productivity were accompanied by greater abundances of 'subsurface'-dwelling calcareous nannofossils (nannoconids) and planktic Foraminifera (rotaliporids). These taxa presumably indicate more stratified surface-water conditions. We suggest that the formation of the Niveau Breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation. This, in turn, caused a decrease in low-latitude deep-water formation and probably an increase in surface-water stratification. The combination of these two mechanisms caused depleted O2 concentrations in the bottom water that increased the preservation potential of organic matter

EPICA Dronning Maud Land EDML ice core drilling protocol

We report on the EPICA Dronning Maud Land (East Antarctica) deep drilling operation. Starting with the scientific questions that led to the outline of the EPICA project, we introduce the setting of sister drillings at NorthGRIP and EPICA Dome C within the European ice-coring community. The progress of the drilling operation is described within the context of three parallel, deep-drilling operations, the problems that occurred and the solutions we developed. Modified procedures are described, such as the monitoring of penetration rate via cable weight rather than motor torque, and modifications to the system (e.g. closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension). Parameters of the drilling (e.g. core-break force, cutter pitch, chips balance, liquid level, core production rate and piece number) are discussed. We also review the operational mode, particularly in the context of achieved core length and piece length, which have to be optimized for drilling efficiency and core quality respectively. We conclude with recommendations addressing the design of the chip-collection openings and strictly limiting the cable-load drop with respect to the load at the start of the run.