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  • 1
    ISSN: 0003-2697
    Keywords: 3-hydroxyisobutyrate ; gas chromatography-mass spectrometry ; isotope analysis ; ketone bodies ; ketone body turnover ; molar percent enrichment
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Analytical Biochemistry 152 (1986), S. 256-261 
    ISSN: 0003-2697
    Keywords: 2-propanol ; acetoacetate ; acetone ; gas-chromatography ; high-performance liquid chromatography ; specific activity
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2021-07-11
    Description: The carbon balance of peatlands is predicted to shift from a sink to a source this century. However, peatland ecosystems are still omitted from the main Earth system models that are used for future climate change projections, and they are not considered in integrated assessment models that are used in impact and mitigation studies. By using evidence synthesized from the literature and an expert elicitation, we define and quantify the leading drivers of change that have impacted peatland carbon stocks during the Holocene and predict their effect during this century and in the far future. We also identify uncertainties and knowledge gaps in the scientific community and provide insight towards better integration of peatlands into modelling frameworks. Given the importance of the contribution by peatlands to the global carbon cycle, this study shows that peatland science is a critical research area and that we still have a long way to go to fully understand the peatland–carbon–climate nexus.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 4
    Publication Date: 2016-08-05
    Description: The increasing accessibility to navigation and offshore oil exploration brings risks of hydrocarbon releases in Arctic waters. Bioremediation of hydrocarbons is a promising mitigation strategy but challenges remain, particularly due to low microbial metabolic rates in cold, ice-covered seas. Hydrocarbon degradation potential of ice-associated microbes collected from the Northwest Passage was investigated. Microcosm incubations were run for 15 days at –1.7°C with and without oil to determine the effects of hydrocarbon exposure on microbial abundance, diversity and activity, and to estimate component-specific hydrocarbon loss. Diversity was assessed with automated ribosomal intergenic spacer analysis and Ion Torrent 16S rRNA gene sequencing. Bacterial activity was measured by 3 H-leucine uptake rates. After incubation, sub-ice and sea-ice communities degraded 94% and 48% of the initial hydrocarbons, respectively. Hydrocarbon exposure changed the composition of sea-ice and sub-ice communities; in sea-ice microcosms, Bacteroidetes (mainly Polaribacter ) dominated whereas in sub-ice microcosms, the contribution of Epsilonproteobacteria increased, and that of Alphaproteobacteria and Bacteroidetes decreased. Sequencing data revealed a decline in diversity and increases in Colwellia and Moritella in oil-treated microcosms. Low concentration of dissolved organic matter (DOM) in sub-ice seawater may explain higher hydrocarbon degradation when compared to sea ice, where DOM was abundant and composed of labile exopolysaccharides.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
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  • 5
    Publication Date: 2015-06-17
    Description: Hydrologic interaction between surface and subsurface water systems has a significant impact on water quality, ecosystems and biogeochemistry cycling of both systems. Distributed models have been developed to simulate this function, but they require detailed spatial inputs and extensive computation time. The SWAT model is a semi-distributed model that has been successfully applied around the world. However it has not been able to simulate the two way exchanges between surface water and groundwater. In this study, the SWAT-LU model – based on a catena method that routes flow across three landscape units (the divide, the hillslope and the valley) – was modified and applied in the floodplain of the Garonne River. The modified model was called SWAT-LUD. Darcy's equation was applied to simulate groundwater flow. The algorithm for surface water level simulation during flooding periods was modified and the influence of flooding on groundwater levels was added to the model. Chloride was chosen as a conservative tracer to test simulated water exchanges. The simulated water exchange quantity from SWAT-LUD was compared with the output of a 2D distributed model, 2SWEM. The results showed that simulated groundwater levels in the LU adjoining the river matched the observed data very well. Additionally, SWAT-LUD model was able to reflect the actual water exchange between the river and the aquifer. It showed that river water discharge has a significant influence on the surface-groundwater exchanges. The main water flow direction in the river/groundwater interface was from groundwater to river, water flowed in this direction accounted for 65 % of the total exchanged water volume. The water mixing occurs mainly during high hydraulic periods. Flooded water was important for the SW-GW exchange process, it accounted for 69 % of total water flowed from the river to the aquifer. The new module also provides the option of simulating pollution transfer occurring at the river/groundwater interface at the catchment scale. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 6
    Publication Date: 2011-12-08
    Description: Understanding the processes controlling peatland carbon (C) sequestration is critical to anticipate potential changes in the global C cycle in response to climate change. Although identification of these factors may be relatively straightforward on seasonal timescales, at centennial to millennial timescales complexities arise because of interactions between climate, vegetation, hydrology and long-term ecological processes. To better understand the factors controlling long-term C accumulation, Holocene rates of C sequestration were quantified from three pristine ombrotrophic peatlands in boreal Quebec, northeastern Canada (52°N, 75–76°W). Bulk density and loss-on-ignition analyses, combined with radiocarbon dating and age–depth modelling, were used to estimate long-term apparent rates of carbon accumulation. Past changes in vegetation and water-table depth were obtained from plant macrofossil and testate amoeba analysis. Earliest regional peat accumulation started ~7520 cal. BP, with long-term rates of C sequestration varying between 14.9 and 22.6 g/m 2 per yr. High C sequestration rates occurred during the mid Holocene when relatively stable Sphagnum section Acutifolia communities were present, while low rates were found during the cooler late Holocene when Cyperaceae and ligneous vegetation were more dominant. However, C sequestration was highly variable among cores, implying that local topography, geomorphology and hydrology, or disturbance factors such as fire, mediate the influence of climate on C accumulation. Reconstructed water-table depths reveal several dry shifts since 3000 cal. BP, suggesting that episodic cold and dry conditions during the late Holocene may have contributed to lower C sequestration rates. Given the intensity of the water-table shifts at these times, we hypothesize that recurrent episodes of frozen subsurface peat might have intensified surface drying. As projected by climate scenarios, anticipated warmer and wetter conditions may lead to greater stability of hummock Sphagna cover and increased C sequestration potential in boreal peatlands.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 7
    Publication Date: 2014-08-22
    Description: Ombrotrophic peatlands (bogs) act as important terrestrial sinks of organic carbon (C). These ecosystems are widespread in coastal maritime regions of eastern Canada. This study aims to evaluate and compare Holocene peatland C dynamics between two maritime ecoclimatic regions along the St. Lawrence North Shore. The investigated bogs are located on two postglacial deltas along the Estuary (Baie-Comeau) and the Gulf of St Lawrence (Havre-St-Pierre) in eastern Quebec. Long-term apparent rates of C accumulation (LORCA) are calculated for eight peat cores, and temporal variations in C accumulation are compared between six peatlands. Our data suggest that long-term C sequestration is affected by a constant anoxic decay, but the LORCA are considerably lower in Havre-St-Pierre (16–46 g C/m 2 /yr) than in Baie-Comeau (53–68 g C/m 2 /yr). The interactions between water table levels, peat humification and C accumulation are also evaluated and suggest an influence of internal (autogenic) processes and feedbacks. The bogs of the two regions show distinct patterns of C sequestration and different sensitivities to climate especially during the late Holocene. These results show that in spite of the internal influences, the regional climate has exerted a pervasive control on primary production in these peatlands over the Holocene.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 8
    Publication Date: 2014-08-22
    Description: Peatlands constitute major sinks of organic carbon (C) and play a key role in the global C cycle. Here, we present a synthesis of peat records from six ecoclimatic regions in Québec, Canada, in order to quantify Holocene patterns of C accumulation and relationships with contemporary climate data. Average long-term apparent rates of C accumulation (LORCA) were calculated for 21 peat cores and range from 10 to 70 g C/m 2 /yr with a mean of 26.1 (standard error of mean (SEM) = 3.6) g C/m 2 /yr, which is slightly higher than the mean value for northern peatlands as a whole (Loisel et al., 2014). We found that regional climate has been a major factor controlling long-term peatland C accumulation and that site-specific factors may explain some variability between sites. Our data show that LORCA tend to decrease with latitude. The lowest LORCA are found in the northernmost peatlands located at the boreal forest/forest-tundra ecotone, whereas the highest values are recorded in the peatlands along the St. Lawrence Estuary, characterized by the highest mean summer temperature, number of growing degree-days above 0 ° C and mean annual precipitation. Temporal variations in Holocene C accumulations rates were synthesized for 16 peat cores, which show high values during the mid-Holocene (6000–4000 cal. yr BP) followed by a decline during the Neoglacial cooling, especially between 2000 and 1200 cal. yr BP. Our study contributes to a better understanding of sensitivity of peatland C balance to climate change in a poorly documented part of the circumboreal region.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
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  • 9
    Publication Date: 2014-08-22
    Description: Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 ± 3% (standard deviation) for Sphagnum peat, 51 ± 2% for non- Sphagnum peat, and at 49 ± 2% overall. Dry bulk density averaged 0.12 ± 0.07 g/cm 3 , organic matter bulk density averaged 0.11 ± 0.05 g/cm 3 , and total carbon content in peat averaged 47 ± 6%. In general, large differences were found between Sphagnum and non- Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 ± 2 (standard error of mean) g C/m 2 /yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25–28 g C/m 2 /yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu .
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 10
    Publication Date: 2013-03-15
    Description: Soil paludification is the main ecosystem process initiating the formation and development of most peatlands in the Northern Hemisphere. Sandy podzolic soils developed on coarse deposits are among a large variety of substrates overgrown by thick peat layers, particularly along the amphi-atlantic coasts of North America and Europe. Whether the podzolic soils beneath peat layers are remnants of former dry environments allowing the morphogenetic development of forest soils or the progressive outcome of natural succession towards full peatland growth is still debated. We have explored a part of this dual facet in documenting the interface between buried podzol profiles and basal peat. Two paludified sites located at the center and at the edge of an extensive plateau bog along the Gulf of St Lawrence were documented based on radiocarbon-dated tree and charcoal macrofossils. Paleosols beneath thick and relatively old (〉 4000 cal. yr BP) peat were composed of slightly cemented, placic B horizons whereas those under thinner and younger (〈 2500 cal. yr BP) peat were made of heavily cemented, ortstein B horizons. Forest soil paludification and peat growth at both sites commenced with the cessation of fire occurrence as evidenced by charcoal fragments in the paleosol matrix beneath Sphagnum peat layers devoid of charcoal fragments. Botanically identified charcoal fragments include several tree species, in particular jack pine ( Pinus banksiana ) presently absent from this part of the continent. The retreat of the species likely occurred after 5500 cal. BP with the cessation of fire occurrence, an indication of a shift in maritime Québec from dry to wetter conditions initiating peat growth and peatland expansion. It is concluded that the genesis and development of podzols with different degrees of soil cementation (placic and ortstein horizons) preceded the inception and development of the plateau bog which have been facilitated by wetter climatic conditions inimical to fire activity. The progressive lateral growth of large ombrotrophic peatlands during the Holocene is also an additional, possible factor influencing the natural occurrence and spread of fire.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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