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  • National Academy of Sciences  (3)
  • PANGAEA  (2)
  • American Association for the Advancement of Science  (1)
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  • 1
    Publication Date: 2023-10-28
    Description: The outflow of Leverett Glacier, a large land-terminating glacier of the Greenland Ice Sheet was sampled over the 2015 ablation season. Dissolved organic carbon (DOC) concentrations, dissolved organic matter (DOM) fluorescence, and hydrogeochemical data (e.g. discharge, specific conductivity, pH, and turbidity) were analyzed to assess changing DOM sources over the melt season. DOC concentrations and red-shifted fluorescence suggest terrestrial inputs from overridden soils dominated DOM early season inputs before progressive dilution with increasing discharge. During the outburst period, supraglacial drainage events disrupted the subglacial drainage system and introduced dominant protein-like fluorescence signatures not observed in basal flow. These results suggest that subglacial hydrology and changing water sources influence exported DOC concentration and DOM composition, differentiated through fluorescence characteristics. The outburst and post-outburst periods were characterized by protein-like fluorescence from supraglacial and potentially subglacial microbial sources.
    Keywords: Campbell Scientific 247-L Conductivity and Temperature Probe; Carbon, organic, dissolved; Carbon, organic, dissolved load; Conductivity; DATE/TIME; Day of the year; Dissolved Organic Matter; DOM; Event label; Flow rate; Fluorescence; Fluorescence, dissolved organic matter, at 317 nm wavelength; Fluorescence, dissolved organic matter, at 368 nm wavelength; Fluorescence, dissolved organic matter, at 416 nm wavelength; Fluorescence, dissolved organic matter, at 425 nm wavelength; Fluorescence, dissolved organic matter, at 483 nm wavelength; Fluorescence spectrometer, AquaLog, HORIBA JobinYvon; glaciers; Greenland; Honeywell Durafet pH sensors; Lachat QuickChem 8500 flow injection autoanalyser; L Atalante; Leverett_glacier_basal_ice; Leverett_glacier_snow; Leverett_glacier_time_series; Nitrogen in nitrate; PARAFAC; Period; pH; Phosphorus in orthophosphate; Pressure transducer, HOBO; Roorkee Industries Suspended Sediment Sampler USDH-48; Shimadzu TOC-L total organic carbon analyzer; SNOW; Snow/ice sample; Suspended particulate matter; Thermo Scientific Dionex IonPac AS11-HC-4μm Anion-Exchange Column fitted to a Thermo Scientific Dionex ICS-5000 Ion Chromatography; ZAIROV
    Type: Dataset
    Format: text/tab-separated-values, 785 data points
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  • 2
    Publication Date: 2024-03-15
    Description: Focusing on algal taxa from two different functional groups on Caribbean coral reefs, we exposed fleshy (Dictyota spp.) and calcifying (Halimeda tuna) macroalgae to ambient and low seawater pH for 25 days in an outdoor experimental system in the Florida Keys. We quantified algal growth, calcification, photophysiology, and DOC production across pH treatments.
    Keywords: Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Aragonite saturation state, standard deviation; Benthos; Bicarbonate ion; Bicarbonate ion, standard deviation; Bottles or small containers/Aquaria (〈20 L); Buoyant mass; Calcification/Dissolution; Calcification rate; Calcification rate, standard deviation; Calcite saturation state; Calcite saturation state, standard deviation; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Calculated using seacarb after Orr et al. (2018); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate ion, standard deviation; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard deviation; Carotenoids; Carotenoids, standard deviation; Chlorophyll a; Chlorophyll a, standard deviation; Chlorophyll b; Chlorophyll b, standard deviation; Chlorophyta; Chromista; Coast and continental shelf; Dictyota sp.; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Fugacity of carbon dioxide in seawater, standard deviation; Growth/Morphology; Halimeda tuna; Laboratory experiment; Macroalgae; Mass, standard deviation; Maximum quantum yield of photosystem II; Maximum quantum yield of photosystem II, standard deviation; Net calcification rate of calcium carbonate, dark; Net calcification rate of calcium carbonate, light; Net photosynthesis rate, oxygen; Net photosynthesis rate, standard deviation; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Oxygen, dissolved; Oxygen, dissolved, standard deviation; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH, standard deviation; Plantae; Primary production/Photosynthesis; Respiration; Respiration rate, oxygen; Respiration rate, oxygen, standard deviation; Salinity; Salinity, standard deviation; Single species; Species; Surface area; Surface area, standard deviation; Temperate; Temperature, water; Temperature, water, standard deviation; Treatment; Type of study; Wet mass; Wet mass, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 240 data points
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  • 3
    Publication Date: 2018-01-02
    Description: Atmospheric nitrogen (N) deposition is an important determinant of N availability for natural ecosystems worldwide. Increased anthropogenic N deposition shifts the stoichiometric equilibrium of ecosystems, with direct and indirect impacts on ecosystem functioning and biogeochemical cycles. Current simulation data suggest that remote tropical forests still receive low atmospheric N deposition due to a lack of proximate industry, low rates of fossil fuel combustion, and absence of intensive agriculture. We present field-based N deposition data for forests of the central Congo Basin, and use ultrahigh-resolution mass spectrometry to characterize the organic N fraction. Additionally, we use satellite data and modeling for atmospheric N source apportionment. Our results indicate that these forests receive 18.2 kg N hectare−1years−1as wet deposition, with dry deposition via canopy interception adding considerably to this flux. We also show that roughly half of the N deposition is organic, which is often ignored in N deposition measurements and simulations. The source of atmospheric N is predominantly derived from intensive seasonal burning of biomass on the continent. This high N deposition has important implications for the ecology of the Congo Basin and for global biogeochemical cycles more broadly.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2015-10-26
    Description: Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high–temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low–molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2to the atmosphere by soils and nearby inland waters.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 2020-11-23
    Description: Trace elements sustain biological productivity, yet the significance of trace element mobilization and export in subglacial runoff from ice sheets is poorly constrained at present. Here, we present size-fractionated (0.02, 0.22, and 0.45 µm) concentrations of trace elements in subglacial waters from the Greenland Ice Sheet (GrIS) and the Antarctic Ice Sheet (AIS). Concentrations of immobile trace elements (e.g., Al, Fe, Ti) far exceed global riverine and open ocean mean values and highlight the importance of subglacial aluminosilicate mineral weathering and lack of retention of these species in sediments. Concentrations are higher from the AIS than the GrIS, highlighting the geochemical consequences of prolonged water residence times and hydrological isolation that characterize the former. The enrichment of trace elements (e.g., Co, Fe, Mn, and Zn) in subglacial meltwaters compared with seawater and typical riverine systems, together with the likely sensitivity to future ice sheet melting, suggests that their export in glacial runoff is likely to be important for biological productivity. For example, our dissolved Fe concentration (20,900 nM) and associated flux values (1.4 Gmol y−1) from AIS to the Fe-deplete Southern Ocean exceed most previous estimates by an order of magnitude. The ultimate fate of these micronutrients will depend on the reactivity of the dominant colloidal size fraction (likely controlled by nanoparticulate Al and Fe oxyhydroxide minerals) and estuarine processing. We contend that ice sheets create highly geochemically reactive particulates in subglacial environments, which play a key role in trace elemental cycles, with potentially important consequences for global carbon cycling.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2013-04-19
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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