99 resultados para åk 4-6


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A uniform chronology for foraminifera-based sea surface temperature records has been established in more than 120 sediment cores obtained from the equatorial and eastern Atlantic up to the Arctic Ocean. The chronostratigraphy of the last 30,000 years is mainly based on published d18O records and 14C ages from accelerator mass spectrometry, converted into calendar-year ages. The high-precision age control provides the database necessary for the uniform reconstruction of the climate interval of the Last Glacial Maximum within the GLAMAP-2000 project.

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The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

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CARD-FISH was performed as previously described in Ruff et al., (2013; doi:10.1371/journal.pone.0072627) with the following modifications. 4-6 µl of 25-fold diluted sediment were used for filtration. Archaeal cell walls were permeabilized with 0.1M HCl for 2 min to detect ANME-3 cells, or Proteinase K solution (15 µg ml-1 (Merck, Darmstadt, Germany) in 0.05 M EDTA (pH 8), 0.1 M Tris-HCl (pH 8), 0.5 M NaCl) for 2-4 min at room temperature for all other archaea. Bacterial cell walls were permeabilized with lysozyme solution (1000kU/ml) for 60 min at 37°. Cells were stained with DAPI (1µg/ml), embedded in mounting medium and counted in 40-60 independent microscopic fields using an Axiophot II epifluorescence microscope (Carl Zeiss, Jena, Germany).

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Among the Siberian shelf seas the Kara Sea is most strongly influenced by riverine runoff with nearly 1500 km fresh water discharge per year. This fresh water, discharged mainly by Ob and Yenisei, contains about 3.1 * 106 and 4.6 * 106 tons of total organic carbon per year, respectively (Gordeev et al. 1996). Little is known about the relevance of this organic material for biological communities, neither for the Kara Sea nor for the adjacent deep basins of the central Arctic Ocean. Aiming at elucidating the fate of fluvial matter transported from the rivers via estuaries into the central Arctic Ocean and the relative importance of marine organic matter being produced such information is crucial. Here we present calculations on the organic carbon demand of the Kara Sea macrozoobenthos based on measured biomass (total wet weight [ww] per 0.25 m ) from quantitative box corer samples and empirical relationships between biomass, annual production, annual respiration, and carbon remineralisation. This bottom-up approach may serve as a first estimate of the carbon remineralization potential of a given zoobenthos community (or area) as long as no data on in situ respiration rates are available. Our data basis comprises 54 stations sampled in summer seasons 1997, 1999 and 2000 in the Kara Sea at water depths between 10 and 68 m. The geographical area represented by stations analysed covers roughly 178 000 km**2, which is about one fifth of the total Kara Sea area. In this area, 290 species of invertebrate macrozoobenthos were identified with polychaeta, Crustacea, mollusca and echinodermata being the most abundant. For all stations analysed, mean biomass values ranged between 4.3 and 778.1 g ww/m**2 with organic carbon demands between 3.5 and 43.2 mg C/m**2/d. For the area of 178 000 km2 a preliminary total consumption of 1.4 * 10**6t Corg/y (equivalent to 21.5 mg C/m**2/d) was calculated for the macrozoobenthos. An extrapolation of our data would lead to an annual carbon demand of about 5-7 * 106 t for the whole Kara Sea macrozoobenthos (or 15.5-21.7 mg C/m2/d).

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An integrated, high-resolution chemostratigraphic (C, O and Sr isotopes) and magnetostratigraphic study through the upper Middle Cambrian - lowermost Ordovician shallow-marine carbonates of the northwestern margin of the Siberian Platform is reported. The interval was analysed at the Kulyumbe section, which is exposed along the Kulyumbe River: an eastern tributary of the Enisej River. It comprises the upper Ust'-Brus, Labaz, Orakta, Kulyumbe, Ujgur, and lower Iltyk formations and includes the Steptoean positive carbon isotopic excursion (SPICE) studied here in detail from upper Cambrian carbonates of the Siberian Platform for the first time. The peak of the excursion, showing d13C positive values as high as +4.6? and least-altered 87Sr/86Sr ratios of 0.70909, is reported herein from the Yurakhian Horizon of the Kulyumbe Formation. The stratigraphic position of the SPICE excursion does not support traditional correlation of the boundary between the Orakta and Labaz formations at Kulyumbe River with its supposedly equivalent level in Australia, Laurentia, South China, and Kazakhstan, where the Glyptagnostus stolidotus and G. reticulatus biozones are known to immediately precede the SPICE excursion and span the Middle-Upper Cambrian boundary. The Cambrian-Ordovician boundary is probably situated in the middle Nyajan Horizon of the Iltyk Formation, in which carbon isotope values show a local maximum below a decrease in the upper part of the Nyajan Horizon, attributed herein to the Tremadocian. A refined magnetic polarity sequence shows that the geomagnetic reversal frequency was very high during the Middle Cambrian at 5-10 reversals per Ma, assuming a total duration of ~10 Ma and up to 100 magnetic intervals in the Middle Cambrian. By contrast, the sequence attributed herein to the Upper Cambrian on chemostratigraphic grounds contains only 10-11 magnetic intervals. Preprint in Open Access hdl:10013/epic.30209.d001

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This data set comprises time series of aboveground community plant biomass (Sown plant community, Weed plant community, Dead plant material, and Unidentified plant material; all measured in biomass as dry weight) and species-specific biomass from the sown species of several experiments at the field site of a large grassland biodiversity experiment (the Jena Experiment; see further details below). Aboveground community biomass was normally harvested twice a year just prior to mowing (during peak standing biomass twice a year, generally in May and August; in 2002 only once in September) on all experimental plots in the Jena Experiment. This was done by clipping the vegetation at 3 cm above ground in up to four rectangles of 0.2 x 0.5 m per large plot. The location of these rectangles was assigned by random selection of new coordinates every year within the core area of the plots. The positions of the rectangles within plots were identical for all plots. The harvested biomass was sorted into categories: individual species for the sown plant species, weed plant species (species not sown at the particular plot), detached dead plant material (i.e., dead plant material in the data file), and remaining plant material that could not be assigned to any category (i.e., unidentified plant material in the data file). All biomass was dried to constant weight (70°C, >= 48 h) and weighed. Sown plant community biomass was calculated as the sum of the biomass of the individual sown species. The data for individual samples and the mean over samples for the biomass measures on the community level are given. Overall, analyses of the community biomass data have identified species richness as well as functional group composition as important drivers of a positive biodiversity-productivity relationship. The following series of datasets are contained in this collection: 1. Plant biomass form the Main Experiment: 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). 2. Plant biomass from the Dominance Experiment: In the Dominance Experiment, 206 grassland plots of 3.5 x 3.5 m were established from a pool of 9 species that can be dominant in semi-natural grassland communities of the study region. 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, 3, 4, 6, and 9 species). 3. Plant biomass from the monoculture plots: In the monoculture plots the sown plant community contains only a single species per plot and this species is a different one for each plot. Which species has been sown in which plot is stated in the plot information table for monocultures (see further details below). The monoculture plots of 3.5 x 3.5 m were established for all of the 60 plant species of the Jena Experiment species pool with two replicates per species like the other experiments in May 2002. All plots were maintained by bi-annual weeding and mowing.

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Recent revisions of the geological time scale by Kent and Gradstein (in press) suggest that, on the average, Cretaceous magnetic anomalies are approximately 10 m.y. older than in Larson and Hilde's (1975) previous time scale. These revised basement ages change estimates for the duration of alteration in the ocean crust, based on the difference between secondary-mineral isochron ages and magnetic isochron-crustal ages, from 3 to approximately 13 m.y. In addition to the revised time scale, Burke et al.'s (1982) new data on the temporal variation of 87Sr/86Sr in seawater allow a better understanding of the timing of alteration and more realistic determinations of water/rock ratios during seawater-basalt interaction. Carbonates from all DSDP sites which reached Layer 2 of Atlantic crust (Sites 105, 332, 417, and 418) are deposited within 10-15 m.y. of crustal formation from solutions with 87Sr/86Sr ratios identical to unaltered or contemporaneous seawater. Comparisons of the revised seawater curve with the 87Sr/86Sr of basement carbonates is consistent with a duration of approximately 10-15 m.y. for alteration in the ocean crust. Our preliminary Sr and 87Sr/86Sr data for carbonates from Hole 504B, on 5.9-m.y.-old crust south of the Costa Rica Rift, suggest that hydrous solutions from which carbonates precipitated contained substantial amounts of basaltic Sr. For this reason, carbonate 87Sr/86Sr cannot be used to estimate the duration of alteration at this site. A basalt-dominated alteration environment at Hole 504B is consistent with heat-flow evidence which indicates rapid sediment burial of crust at the Costa Rica Rift, sealing it from access by seawater and resulting in unusually low water/rock ratios during alteration.

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Cruise Mn-74-02 of the R/V MOANA WAVE was the second part of the field work of the NSF/IDOE Inter-University Ferromanganese Research Program in 1974, and we gratefully acknowledge the support of the office for the International Decade of Ocean Exploration and the Office of Oceanographic Facilities and Support. This program was designed to investigate the origin, growth, and distribution of copper/nickel-rich manganese nodules in the Pacific Ocean. The field effort was designed to satisfy sample requirements of the fifteen principal investigators, while increasing general knowledge of the copper/nickel-rich nodule deposits of the equatorial Pacific. This report is the second of a series of cruise reports designed to assist sample requests for documented nodules, sediment, and water samples so that laboratory results can be realistically compared and related to the environment of nodule growth. Nodule samples and bathymetric and navigational data are archived at the Hawaii Institute of Geophysics, University of Hawaii. Bulk chemical analyses of nodules and reduction of survey data were carried out at Hawaii. Sediment cores were stored at the University of Hawaii and at Scripps Institution of Oceanography. The SIO analytical facility provided stratigraphic data on sediment chemistry.