Concentrations and carbon isotopic compositions of organic and inorganic compounds in sediment porewaters at IODP Site U1329

Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, d13C values of acetate span a wide range from -46.0 per mill to -11.0 per mill vs. VPDB and change systematically with sediment depth. In contrast, d13C values of both the bulk dissolved organic carbon (DOC) (-21.6 ± 1.3 per mill vs. VPDB) and the low-molecular-weight compound lactate (-20.9 ± 1.8 per mill vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1 per mill depleted and up to 9.1 per mill enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron-accepting process. Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments.

Radiocarbon dating, sedimentation rate, granulometry and organic carbon content of ODP Leg 182 sites

This data report presents sedimentological (grain size) and geochemical (X-ray diffraction, total organic carbon, accelerator mass spectrometry radiocarbon, and percent carbonate) information obtained from the western transect (Sites 1132, 1130, and 1134) and the eastern transect (Sites 1129, 1131, and 1127) in the Great Australian Bight during Leg 182. The purpose is to quantify changing rates of sediment accumulation and changes in sediment type from the late Pleistocene and Holocene, in order to relate these changes to the well-known sea level curve that exists for this time frame. Ultimately, these data can be used to more effectively interpret lithologic variations deeper in the Pleistocene succession, which most likely represent orbitally forced sea level events.

Distribution of organic carbon in surface sediments covered during SONNE cruise SO184

Sediments were sampled and oxygen profiles of the water column were determined in the Indian Ocean off west and south Indonesia in order to obtain information on the production, transformation, and accumulation of organic matter (OM). The stable carbon isotope composition (d13Corg) in combination with C/N ratios depicts the almost exclusively marine origin of sedimentary organic matter in the entire study area. Maximum concentrations of organic carbon (Corg) and nitrogen (N) of 3.0% and 0.31%, respectively, were observed in the northern Mentawai Basin and in the Savu and Lombok basins. Minimum d15N values of 3.7 per mil were measured in the northern Mentawai Basin, whereas they varied around 5.4 per mil at stations outside this region. Minimum bottom water oxygen concentrations of 1.1 mL L**1, corresponding to an oxygen saturation of 16.1%, indicate reduced ventilation of bottom water in the northern Mentawai Basin. This low bottom water oxygen reduces organic matter decomposition, which is demonstrated by the almost unaltered isotopic composition of nitrogen during early diagenesis. Maximum Corg accumulation rates (CARs) were measured in the Lombok (10.4 g C m**-2 yr**-1) and northern Mentawai basins (5.2 g C m**-2 yr**-1). Upwelling-induced high productivity is responsible for the high CAR off East Java, Lombok, and Savu Basins, while a better OM preservation caused by reduced ventilation contributes to the high CAR observed in the northern Mentawai Basin. The interplay between primary production, remineralisation, and organic carbon burial determines the regional heterogeneity. CAR in the Indian Ocean upwelling region off Indonesia is lower than in the Peru and Chile upwellings, but in the same order of magnitude as in the Arabian Sea, the Benguela, and Gulf of California upwellings, and corresponds to 0.1-7.1% of the global ocean carbon burial. This demonstrates the relevance of the Indian Ocean margin off Indonesia for the global OM burial.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2002)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2005)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2006)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Coccolithosphores and fossil organic compounds of sediment core MD01-2444

This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic d13Ccc and planktonic d18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution over the last 70,000 years: the Holocene and the stadial and interstadial modes. The different alternatives are described by means of elements such as nutrients; upwelling phenomena; temperatures at surface and subsurface level; or the arrival of surface turbid, fresh, and cold waters due to icebergs, low sea level, increased aridity, and dust. During the Holocene, moderate primary productivity was observed (mainly concentrated in E. huxleyi specimens); surface temperatures were at maxima while the water column was highly ventilated by northern-sourced polar deep waters and warmer subsurface, nutrient-poor subtropical waters. Over most of the last glacial stadials, surface productivity weakened (higher F. profunda and reworked specimen percentages and lower diunsaturated and triunsaturated C37 alkenones); the arrival of cold Arctic surface waters traced by tetraunsaturated C37 peaks and large E. huxleyi, together with powerful ventilated southern-sourced polar deep waters, disturbed, in all likelihood, the delicate vertical equilibrium while preventing significant upwelling mixing. Finally, during the last glacial interstadials (lower F. profunda percentages, nonreworked material, and higher diunsaturated and triunsaturated C37 alkenones) a combined signal is observed: warm surface temperatures were concurrent with generally low oxygenation of the deep-sea floor, moderate arrival of northern-sourced deep waters, and subsurface cold, nutrient-rich, recently upwelled waters, probably of polar origin; these particular conditions may have promoted vertical mixing while enhancing surface primary productivity (mainly of Gephyrocapsa specimens).

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2003)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2007)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2008)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Calcium isotope ratios of pore fluids and solid phase of organic rich sediments

Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (d44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of d44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, d44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the d44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these sites (the actual rates could be significantly slower) because other processes that impact the calcium isotope composition of sedimentary pore fluid have not been included. The results provide direct geochemical evidence for the anecdotal observation that the best-preserved carbonate fossils are often found in clay or organic-rich sedimentary horizons. The results also suggest that the presence of clay minerals has a strong passivating effect on the surfaces of biogenic carbonate minerals, slowing dissolution dramatically even in relation to the already-slow rates typical of carbonate-rich sediments.

Dissolved organic carbon in soil solution of the Jena Experiment (Main Experiment, year 2004)

This data set contains measurements of dissolved organic carbon in samples of soil water collected 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. In April 2002 glass suction plates with a diameter of 12 cm, 1 cm thickness and a pore size of 1-1.6 mm (UMS GmbH, Munich, Germany) were installed in depths of 10, 20, 30 and 60 cm to collect soil solution. The sampling bottles were continuously evacuated to a negative pressure between 50 and 350 mbar, such that the suction pressure was about 50 mbar above the actual soil water tension. Thus, only the soil leachate was collected. Cumulative soil solution was sampled biweekly and analyzed for dissolved organic carbon concentration by a high TOC elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Samples were analyzed as soon as possible and stored at 4°C if necessary. Often in summer, no free soil solution was available for collection, especially in the upper soil layers. Annual mean values of measured biweekly concentrations of dissolved organic carbon are provided.

Organic geochemical comparison of Cretaceous green and black claystones at DSDP Hole 75-530A

Three pairs of Upper Cretaceous black shales and adjacent green claystones from Hole 530A were analyzed to compare types and amounts of organic matter and lipids and to seek information about their environments of deposition. The organic-carbon-rich black shales have C/N ratios nearly seven times those of the organic-carbon-lean green claystones. The lipid content of organic matter in the black shales is about ten times less than in adjacent green layers. Organic matter in both types of rocks is thermally immature, and distributions of alkanoic acids, alkanols, sterols, and alkanes contain large amounts of terrigenous components. Pristane/phytane ratios of less than one suggest that younger Turonian sediments were laid down under anoxic conditions, but ratios greater than one suggest that older Turonian Cenomanian deposits accumulated in a more oxic environment. Closely bedded green and black layers have very similar types of lipid distributions and differ primarily in concentrations, although black shales contain somewhat larger amounts of terrigenous lipid components. Geochemical and stratigraphic evidence suggests much of the organic matter in these samples originated on the African continental margin and was transported to the Angola Basin by turbidity flow. Rapid reburial of organic-carbon-rich sediments led to formation of the black shales.

Dissolved organic matter composition derived from FT-ICR-MS analyses during HEINCKE cruise HE361

Dissolved organic matter (DOM) is the main substrate and energy source for heterotrophic bacterioplankton. To understand the interactions between DOM and the bacterial community (BC), it is important to identify the key factors on both sides in detail, chemically distinct moieties in DOM and the various bacterial taxa. Next-generation sequencing facilitates the classification of millions of reads of environmental DNA and RNA amplicons and ultrahigh-resolution mass spectrometry yields up to 10,000 DOM molecular formulae in a marine water sample. Linking this detailed biological and chemical information is a crucial first step toward a mechanistic understanding of the role of microorganisms in the marine carbon cycle. In this study, we interpreted the complex microbiological and molecular information via a novel combination of multivariate statistics. We were able to reveal distinct relationships between the key factors of organic matter cycling along a latitudinal transect across the North Sea. Total BC and DOM composition were mainly driven by mixing of distinct water masses and presumably retain their respective terrigenous imprint on similar timescales on their way through the North Sea. The active microbial community, however, was rather influenced by local events and correlated with specific DOM molecular formulae indicative of compounds that are easily degradable. These trends were most pronounced on the highest resolved level, that is, operationally defined 'species', reflecting the functional diversity of microorganisms at high taxonomic resolution.