Soil carbon in the Jena Experiment from intensive sampling campaigns (only block 2 Main Experiment up to 1 m depth, year 2002)

This data set contains soil carbon measurements (Organic carbon, inorganic carbon, and total carbon; all measured in dried soil samples) from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Stratified soil sampling to a depth of 1 m was performed before sowing in April 2002. Three independent samples per plot were taken of all plots in block 2 using a motor-driven soil column cylinder (Cobra, Eijkelkamp, 8.3 cm in diameter). Soil samples were dried at 40°C and segmented to a depth resolution of 5 cm giving 20 depth subsamples per core. All samples were analyzed independently. All soil samples were passed through a sieve with a mesh size of 2 mm. Rarely present visible plant remains were removed using tweezers. Total carbon concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s**-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany). We measured inorganic carbon concentration by elemental analysis at 1150°C after removal of organic carbon for 16 h at 450°C in a muffle furnace. Organic carbon concentration was calculated as the difference between both measurements of total and inorganic carbon.

Soil carbon in the Jena Experiment (all blocks Main Experiment up to 30cm depth, year 2004)

This data set contains soil carbon measurements (Organic carbon, inorganic carbon, and total carbon; all measured in dried soil samples) from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Soil sampling and analysis: Stratified soil sampling was performed in April 2004 to a depth of 30 cm. Three samples per plot were taken using a split tube sampler with an inner diameter of 4.8 cm (Eijkelkamp Agrisearch Equipment, Giesbeek, the Netherlands). Sampling locations were less than 30 cm apart from sampling locations in 2002. Soil samples were segmented into 5 cm depth segments in the field (resulting in six depth layers) and made into composite samples per depth. Subsequently, samples were dried at 40°C. All soil samples were passed through a sieve with a mesh size of 2 mm. Because of much higher proportions of roots in the soil, samples in years after 2002 were further sieved to 1 mm according to common root removal methods. No additional mineral particles were removed by this procedure. Total carbon concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s**-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany). We measured inorganic carbon concentration by elemental analysis at 1150°C after removal of organic carbon for 16 h at 450°C in a muffle furnace. Organic carbon concentration was calculated as the difference between both measurements of total and inorganic carbon.

Inorganic and organic geochemistry and sediment descriptions at DSDP Hole 93-603B

About one hundred samples of sediments and rocks recovered in Hole 603B were analyzed for type, abundance, and isotopic composition of organic matter, using a combination of Rock-Eval pyrolysis, C-H-N-S elemental analysis, and isotope-ratio mass spectrometry. Concentrations of major, minor, and trace inorganic elements were determined with a combination of X-ray fluorescence and induction-coupled plasma spectrometry. The oldest strata recovered in Hole 603B (lithologic Unit V) consist of interbedded light-colored limestones and marlstones, and black calcareous claystones of Neocomian age. The inorganic and organic geochemical results suggest a very terrigenous aspect to the black claystones. The organic geochemical results indicate that the limestones and marlstones contain a mixture of highly degraded marine and terrestrial organic matter. Comparison of the Neocomian carbonates at Site 603 with those on the other side of the North Atlantic, off Northwest Africa at Site 367, shows that the organic matter at Site 367 contains more marine organic matter, as indicated by higher pyrolysis hydrogen indices and lighter values of d13C. Comparison of inorganic geochemical results for the carbonate lithologies at Site 603 with those for carbonate lithologies at Site 367 suggests that the Site 603 carbonates may contain clastic material from both North American and African sources. The black claystones at Site 603, on the other hand, probably were derived almost entirely from North American clastic sources. Lithologic Unit IV overlying the Neocomian carbonates, consists of interbedded red, green, and black claystones. The black claystones at Site 603 contain more than ten times the organic carbon concentration of the interbedded green claystones. The average concentration of organic carbon in the black claystones (2.8%), however, is low relative to most mid-Cretaceous black claystones and shales in the Atlantic, particularly those found off Northwest Africa. The geochemical data all suggest that the organic matter in the black claystones is more abundant but generally more degraded than the organic matter in the green claystones, and that it was derived mainly from terrestrial sources and deposited in oxygenated bottom waters. The increased percentage of black claystone beds in the upper Cenomanian section, and the presence of more hydrogen-rich organic matter in this part of the section, probably resulted from the increased production and accumulation of marine organic matter that is represented worldwide near the Cenomanian/Turonian boundary in deep-sea and land sections. A few upper Cenomanian black claystone samples that have hydrogen indices > 150 also contain particularly high concentrations of V and Zn. Most samples of black claystone, however, are not particularly metal-rich compared with other black claystones and shales. Compared with red claystones from lithologic Unit IV, the green and black claystones are enriched in many trace transition elements, especially V, Zn, Cu, Co, and Pb. The main difference between the "carbonaceous" claystones of lithologic Unit IV and "variegated" or "multicolored" claystones of the overlying Upper Cretaceous to lower Tertiary Unit III is the absence of black claystone beds. As observed at several other sites (105 and 386), the multicolored claystones at Site 603 are somewhat enriched in several trace transition elements-especially Cu, Ni, and Cr-relative to most deep-sea clays. The multicolored claystones are not enriched in Fe and Mn, and therefore are not "metalliferous" sediments in the sense of those found at several locations in the eastern Pacific. The source of the slightly elevated concentrations of transition metals in the multicolored claystones probably is upward advection and diffusion of metals from the black claystones of the underlying Hatteras Formation. The red, orange, and green claystone beds of lithologic Unit II (Eocene), like those of Unit III, really represent a continuation of deposition of multicolored claystone that began after the deposition of the Neocomian carbonates. The color of the few black beds that occur within this unit results from high concentrations of manganese oxide rather than high concentrations of organic matter.

Organic geochemistry of ODP Leg 107 sediments

The Rock-Eval pyrolysis of rock samples and the elemental analysis of kerogens show clear differences between Messinian black shales and Pliocene-Pleistocene sapropels recovered during ODP Leg 107. The Messinian black shales are characterized by a large variety of compositions which probably reflects a great diversity of depositional and diagenetic paleoenvironments. In contrast, the Pliocene-Pleistocene sapropels, occurring as discrete layers in nannofossil oozes barren of organic carbon, constitute a rather homogeneous group in terms of organic content. A considerable contribution of terrestrial organic matter in the sapropels could mean that an identical phenomenon of terrestrial input has been periodically reproduced in the basin. The maturity and the nature of the organic matter are discussed with respect to anomalous values recorded for Tmax parameter.

Organic carbon, calcium carbonate and carbon/nitrogen ratio at DSDP Leg 93 sites

A large number of samples of nonlithified and lithified sediments from Leg 93 sites were analyzed for their contents of organic carbon and calcium carbonate. An average of two samples was selected from every core for carbonate determination; organic carbon was measured in most of these samples. Nearly all of these analyses were performed on board Glomar Challenger for samples from Sites 603 and 604. Site 605 samples, plus some of the deeper samples from Hole 603B, were analyzed at the University of Michigan. The procedures used in both cases were virtually the same, and their results compared well. Organic carbon analyses were done using a Hewlett- Packard 185-B CHN Analyzer. Portions of samples selected for calcium carbonate determinations were treated with dilute HC1 to remove carbonate, washed with deionized water, and dried at 110°C. A Cahn Electrobalance was used to weight 20-mg samples of sediment for CHN analysis. Samples were combusted at 1050°C in the presence of an oxidant, and the volumes of the evolved gases determined as measures of the C, H, and N contents of sediment organic matter. Areas of gas peaks were determined and compared to those of rock standards of known carbon and nitrogen contents. These values were used to standardize instrument response so that C/N atomic ratios could be reported. Organic carbon concentrations were calculated on the basis of sediment dry weight. Hydrogen elemental analysis with the procedure used is untrustworthy because of the variable amounts of clay minerals and their hydrates, hence hydrogen values are not reported for samples analyzed by this method.

Fe-Mn crusts from the Atlantic Ocean

Mineral and chemical compositions of a set of crust samples collected from the North, Central and South Atlantic were examined by means of analytical electron microscopy and ICP-MS, chemical, and microchemical elemental analysis. Vernadite, asbolane, and goethite are dominant mineral phases of the crusts, ferrihydrite is minor, hematite and feroxyhyte are rare. The samples show wide variability in major and trace element contents; however, their characteristic geochemical signatures indicate hydrogenous origin. A comparison between compositions of oceanic hydrogenous and hydrothermal crusts and metalliferous hydrothermal sediments from different ocean areas suggests that the geochemical approach may be insufficient in some cases and fail to identify hydrothermal input in ferromanganese crusts of mixed composition.

Elemental contents, non-carbonate, fatty acids and alcohols analysis from different Holes of IODP Expedition 310

During IODP Expedition 310 (Tahiti Sea Level), drowned Pleistocene-Holocene barrier-reef terraces were drilled on the slope of the volcanic island. The deglacial reef succession typically consists of a coral framework encrusted by coralline algae and later by microbialites; the latter make up < 80% of the rock volume. Lipid biomarkers were analyzed in order to identify organisms involved in reef-microbialite formation at Tahiti, as the genesis of deglacial microbialites and the conditions favoring their formation are not fully understood. Sterols plus saturated and monounsaturated short-chain fatty acids predominantly derived from both marine primary producers (algae) and bacteria comprise 44 wt% of all lipids on average, whereas long-chain fatty acids and long-chain alcohols derived from higher land plants represent an average of only 24 wt%. Bacterially derived mono-O-alkyl glycerol ethers (MAGEs) and branched fatty acids (10-Me-C16:0; iso- and anteiso-C15:0 and -C17:0) are exceptionally abundant in the microbial carbonates (average, 19 wt%) and represent biomarkers of intermediate-to-high specificity for sulfate-reducing bacteria. Both are relatively enriched in 13C compared to eukaryotic lipids. No lipid biomarkers indicative of cyanobacteria were preserved in the microbialites. The abundances of Al, Si, Fe, Mn, Ba, pyroxene, plagioclase, and magnetite reflect strong terrigenous influx with Tahitian basalt as the major source. Chemical weathering of the basalt most likely elevated nutrient levels in the reefs and this fertilization led to an increase in primary production and organic matter formation, boosting heterotrophic sulfate reduction. Based on the observed biomarker patterns, sulfate-reducing bacteria were apparently involved in the formation of microbialites in the coral reefs off Tahiti during the last deglaciation.

Image analysis from TEM and AFM micrograph, Table S1, S2, S3, Figure S1, Figure S2

We report on metal enrichment along a natural pH gradient owing to increased CO2 degassing at cold, shal- low seeps of Vulcano Island in the Mediterranean Sea, off Sicily. We assessed composition of unfiltered and filtered seawater (b100 nm) along acidic zones ranging between ambient and pH 5, and showed that most seep derived elements are present as nanoclusters which then aggregate into larger colloids while mixing with ambient seawater along a pH gradient. Size and elemental composition of such naturally occurring nanoparticles assessed by modern characterisation methods were in good agreement with the results from conventional analytical methods. We provide analytical evidence for the presence in the water column of a large fraction of seep derived ele- ments (e.g. approximately 50% of iron, over 80% of Mn, 100% of Cr, S and Zn) in the form of nano sized par- ticles (e.g. b100 nm) even at typical open ocean pHs. We launch in situ sampling protocols and sample preparation procedures for multi-method suitable to obtain accurate measurements on nanoparticles from environmental samples. Based on our results a first insight to the formation of natural nanoparticles at cold CO2 seeps is presented and the persistence of such nano-clusters in the surrounding seawater is stipulated.

Chemical and isotopic analysis of bulk organic matter and hydrocarbon biomarkers from IODP Holes 311-U1327C, 311-U1328B and 311-U1328C

The chemical and isotopic compositions of sedimentary organic matter (SOM) from two mid-slope sites of the northern Cascadia margin were investigated during Integrated Ocean Drilling Program (IODP) Expedition 311 to elucidate the organic matter origins and identify potential microbial contributions to SOM. Gas hydrate is present at both locations (IODP Sites U1327 and U1328), with distinct patterns of near-seafloor structural accumulations at the cold seep Site U1328 and deeper stratigraphic accumulations at the slope-basin Site U1327. Source characterization and evidence that some components of the organic matter have been diagenetically altered are determined from the concentrations and isotopic compositions of hydrocarbon biomarkers, total organic carbon (TOC), total nitrogen (TN) and total sulfur (TS). The carbon isotopic compositions of TOC (d13C TOC = -26 to -22 per mil) and long-chain n-alkanes (C27, C29 and C31, d13C = -34 to -29 per mil) suggest the organic matter at both sites is a mixture of 1) terrestrial plants that employ the C3 photosynthetic pathway and 2) marine algae. In contrast, the d15N TN values of the bulk sediment (+4 to +8 per mil) are consistent with a predominantly marine source, but these values most likely have been modified during microbial organic matter degradation. The d13C values of archaeal biomarker pentamethylicosane (PMI) (-46.4 per mil) and bacterial-sourced hopenes, diploptene and hop-21-ene (-40.9 to -34.7 per mil) indicate a partial contribution from methane carbon or a chemoautotrophic pathway. Our multi-isotope and biomarker-based conclusions are consistent with previous studies, based only on the elemental composition of bulk sediments, that suggested a mixed marine-terrestrial organic matter origin for these mid-slope sites of the northern Cascadia margin.

Elemental and stable isotopic composition of some metalliferous and pelagic sediments at DSDP Leg 70 Holes

Nontronite, the main metalliferous phase of the Galapagos mounds, occurs at subsurface depths of about 2 to 20 meters; Mn-oxide material is limited to the upper 2 meters of the mounds. The nontronite forms intervals of up to a few meters' thickness, consisting essentially of 100% nontronite granules, which alternate with intervals of normal pelagic sediment. Electron microprobe analyses of nontronite granules from different core samples indicate that: (1) there is little difference in major element composition between nontronites from varying locations within the mounds, with adjacent granules from a given sample having very similar compositions; (2) individual granules show little internal variation in composition. This indicates that the granules are composed of a single mineral of essentially constant composition, consistent with relatively uniform conditions of Eh and composition during nontronite formation. Mn-oxide crusts have very low Fe contents, a feature characteristic of rapidly deposited Mn-oxide crusts formed under hydrothermal influences. The rare-earth element (REE) abundances of the nontronites are generally extremely low, totalling less than several ppm. Two samples have the negatively Ce anomaly typical of authigenic precipitates formed relatively rapidly from seawater. A Mn-oxide crust sample has low REE contents, typical of Mn-oxide crusts formed under hydrothermal influences, but no negative Ce anomaly. A sample of unusual Mn-Fe-oxide mud has relatively high REE concentrations and a seawater-type pattern; both of these features are also found for metalliferous sediments from the East Pacific Rise. The oxygen and hydrogen isotopic composition of the nontronites define a restricted field within a d18O-dD plot. In manganiferous sediments, d18O and dD appear to decrease with increase in the Mn-oxide content of the sediment. From the d18O values of the nontronites, formation temperatures in the range of about 20-30°C have been estimated. By comparison, temperatures of up to 11.5 °C at a 9-meter depth have been directly measured within the mounds (Corliss et al., 1979), and heat-flow data suggest present basement/sediment interface temperatures of 15-25°C. In a plot of Fe + Mn vs. d18O, the Mn-oxide crust and Mn-Fe-ooze plot near the tie-lines for authigenic Mn nodules and silicate phases, implying that they have formed in isotopic equilibrium with seawater at or close to bottom-water temperatures.