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  • 2010-2014  (6)
  • 1995-1999  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 719-724 
    ISSN: 0044-2313
    Keywords: Undecahydroaza-nido-undecaborate(2-) ; azametalla-closo-dodecaboranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azametalla-closo-dodecaboraneAus nido-NB10H13 erhält man mit der doppelten Menge an K[BHEt3] das Azaborat K2[nido-NB10H11]. Das Anion [NB10H112-] ist isoelektronisch mit [C2B9H11]2-. Es reagiert mit [{η6-(C6R6)RuCl2}2] (R = H, Me), [{η5-(C5Me5)RhCl2}2] oder [Ni(PPh3)2Cl2] zu den Azametalla-closo-dodecaboranen MNB10H11 mit M = (C6Me6)Ru (2), (C6H6)Ru (3), (C5Me5)Rh (4) bzw. (Ph3P)2Ni (5). Aus K2[NB10H11] und CoCl2 läßt sich das Azametallaboran K[Co(NB10H11)2] (6) gewinnen, in welchem das Co-Atom sandwichartig von zwei [NB10H11]2--Ionen koordiniert wird. Vom Produkt 2 · CH2Cl2 liegt eine Röntgenstrukturanalyse vor. Die Produkte 2-6 lassen sich vom ikosaedrisch gebauten Anion [B12H12]2- dadurch ableiten, daß eine BH2--Einheit durch das isoelektronische Nitren NH und eine BH-Einheit durch das isolobale Metallkomplex-Fragment M ersetzt werden. Das N-Atom ist in den Clustergerüsten 2-6 jeweils sechsfach koordiniert.
    Notes: The azaborate K2[nido-NB10H11] is gained from nido-NB10H13 and K[BHEt3] in a 1:2 ratio. The anion [NB10H11]2-, which is isoelectronic with [C2B9H11]2-, reacts with [{η6-(C6R6) · RuCl2}2] (R = H, Me), [{η5-(C5Me5)RhCl2}2], or [Ni(PPh3)2Cl2] to give the azametalla-closo-dodecaboranes MNB10H11 with M = (C6Me6)Ru (2), (C6H6)Ru (3), (C5Me5)Rh (4), and (Ph3P)2Ni (5), respectively. The azametallaborane K[Co(NB10H11)2] (6), which contains a sandwich-type coordinated Co atom, is formed from K2[NB10H11] and CoCl2. The structure of 2 · CH2Cl2 was determined by X-ray diffraction. The products 2-6 can be derived from the icosahedral anion [B12H12]2- on replacing a BH2- moiety by the isoelectronic nitrene NH and a BH moiety by the isolobal metal-complex fragment M. The N atom is six-coordinated in the cluster skeletons 2-6.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2013-07-17
    Description: Phytoplankton and bacteria are sensitive indicators of environmental change. The temporal development of these key organisms was monitored from 1988 to the end of 2007 at the time series station Boknis Eck in the western Baltic Sea. This period was characterized by the adaption of the Baltic Sea ecosystem to changes in the environmental conditions caused by the conversion of the political system in the southern and eastern border states, accompanied by the general effects of global climate change. Measured variables were chlorophyll, primary production, bacteria number, -biomass and -production, glucose turnover rate, macro-nutrients, pH, temperature and salinity. Negative trends with time were recorded for chlorophyll, bacteria number, bacterial biomass and bacterial production, nitrate, ammonia, phosphate, silicate, oxygen and salinity while temperature, pH, and the ratio between bacteria numbers and chlorophyll increased. Strongest reductions with time occurred for the annual maximum values, e.g. for chlorophyll during the spring bloom or for nitrate during winter, while the annual minimum values remained more stable. In deep water above sediment the negative trends of oxygen, nitrate, phosphate and bacterial variables as well as the positive trend of temperature were similar to those in the surface while the trends of salinity, ammonia and silicate were opposite to those in the surface. Decreasing oxygen, even in the surface layer, was of particular interest because it suggested enhanced recycling of nutrients from the deep hypoxic zones to the surface by vertical mixing. The long-term seasonal patterns of all variables correlated positively with temperature, except chlorophyll and salinity. Salinity correlated negatively with all bacterial variables (as well as precipitation) and positively with chlorophyll. Surprisingly, bacterial variables did not correlate with chlorophyll, which may be inherent with the time lag between the peaks of phytoplankton and bacteria during spring. Compared to the 20-yr averages of the environmental and microbial variables, the strongest negative deviations of corresponding annual averages were measured about ten years after political change for nitrate and bacterial secondary production (~ −60%), followed by chlorophyll (−50%) and bacterial biomass (−40%). Considering the circulation of surface currents in the Baltic Sea we interpret the observed patterns of the microbial variables at the Boknis Eck time series station as a consequence of the improved management of water resources after 1989 and – to a minor extent – the trends of the climate variables salinity and temperature.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2019-09-23
    Description: Ocean acidification is elicited by anthropogenic carbon dioxide emissions and resulting oceanic uptake of excess CO2 and might constitute an abiotic stressor powerful enough to alter marine ecosystem structures. For surface waters in gas-exchange equilibrium with the atmosphere, models suggest increases in CO2 partial pressure (pCO2) from current values of ca. 390 μatm to ca. 700–1,000 μatm by the end of the century. However, in typically unequilibrated coastal hypoxic regions, much higher pCO2 values can be expected, as heterotrophic degradation of organic material is necessarily related to the production of CO2 (i.e., dissolved inorganic carbon). Here, we provide data and estimates that, even under current conditions, maximum pCO2 values of 1,700–3,200 μatm can easily be reached when all oxygen is consumed at salinities between 35 and 20, respectively. Due to the nonlinear nature of the carbonate system, the approximate doubling of seawater pCO2 in surface waters due to ocean acidification will most strongly affect coastal hypoxic zones as pCO2 during hypoxia will increase proportionally: we calculate maximum pCO2 values of ca. 4,500 μatm at a salinity of 20 (T = 10 °C) and ca. 3,400 μatm at a salinity of 35 (T = 10 °C) when all oxygen is consumed. Upwelling processes can bring these CO2-enriched waters in contact with shallow water ecosystems and may then affect species performance there as well. We conclude that (1) combined stressor experiments (pCO2 and pO2) are largely missing at the moment and that (2) coastal ocean acidification experimental designs need to be closely adjusted to carbonate system variability within the specific habitat. In general, the worldwide spread of coastal hypoxic zones also simultaneously is a spread of CO2-enriched zones. The magnitude of expected changes in pCO2 in these regions indicates that coastal systems may be more endangered by future global climate change than previously thought.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2019-09-23
    Description: The Boknis Eck (BE) time series station, initiated in 1957, is one of the longest-operated time series stations worldwide. We present the first statistical evaluation of a data set of nine physical, chemical and biological parameters in the period of 1957–2013. In the past three to five decades, all of the measured parameters underwent significant long-term changes. Most striking is an ongoing decline in bottom water oxygen concentration, despite a significant decrease of nutrient and chlorophyll a concentrations. Temperature-enhanced oxygen consumption in the bottom water and a prolongation of the stratification period are discussed as possible reasons for the ongoing oxygen decline despite declining eutrophication. Observations at the BE station were compared with model output of the Kiel Baltic Sea Ice Ocean Model (BSIOM). Reproduced trends were in good agreement with observed trends for temperature and oxygen, but generally the oxygen concentration at the bottom has been overestimated.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2019-09-23
    Description: Dissolved CH4 was measured in the water column at the Boknis Eck (BE) time series station in the Eckernförde Bay (SW Baltic Sea) on a monthly basis from June 2006 to November 2008. The water column at BE was always supersaturated with CH4 and, therefore, CH4 was released to the atmosphere throughout the sampling period: the mean CH4 surface (1 m) saturation at BE was 554±317%. A pulse of enhanced CH4 emissions occurs when the CH4 accumulation in the hypoxic bottom layer during summer is terminated in late summer/autumn. We did not detect a straightforward relationship between periods of enhanced CH4 in the bottom layer and hypoxic events at BE: the sedimentary release of CH4 seemed to be mainly triggered by sedimenting organic material from phytoplankton blooms. We conclude that future CH4 emissions from BE will be determined by the intensity of phytoplankton blooms, which in turn will be influenced by eutrophication. However, hypoxic events seem to have only a modulating effect on the enhancement of sedimentary methanogenesis and the subsequent release of CH4 to the water column.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2019-09-23
    Description: Salinity, temperature, and O2 have been recorded on a monthly basis at the Boknis Eck Time Series Station (BE; Eckernförde Bay, SW Baltic Sea) since April 1957 with only two major breaks (1976-78 and 1983-1985). Chlorophyll a measurements started in 1960 and nutrient data (NO2-, NO3-, NH4+, PO4 3-, SiO4 2-) are available since March 1979. Here we present a short introduction to the long-term trends observed at BE and selected results of ongoing projects covering different topics from the surface microlayer and the water column to the sediments at BE. On the basis of a preliminary analysis of the long-term records of surface water temperature, oxygen in 25m, and dissolved nutrients we conclude that BE is affected by both regional processes and global processes detectable as eutrophication and warming of the surface water, respectively. The number of events with extremely depleted O2 concentrations (hypoxia/anoxia) in the bottom layer has been increasing during the last 25 years. Moreover, BE is site of signifi cant emissions of climate relevant trace gases such as methane.
    Type: Article , NonPeerReviewed
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  • 7
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 8
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    Wiley-VCH
    In:  In: Methods of Seawater Analysis. , ed. by Grasshoff, K., Kremling, K. and Ehrhardt, M. Wiley-VCH, Weinheim, Germany, pp. 399-405. 3. edition ISBN 3-527-29589-5
    Publication Date: 2020-04-01
    Type: Book chapter , NonPeerReviewed
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  • 9
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    Wiley-VCH
    In:  In: Methods of Seawater Analysis. , ed. by Grasshoff, K., Kremling, K. and Ehrhardt, M. Wiley-VCH, Weinheim, Germany, pp. 159-228. 3 ISBN 3-527-29589-5
    Publication Date: 2020-04-02
    Type: Book chapter , PeerReviewed
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  • 10
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    Wiley-VCH
    In:  In: Methods of Seawater Analysis. , ed. by Grasshoff, K., Kremling, K. and Ehrhardt, M. Wiley-VCH, Weinheim, pp. 75-89. 3. edition ISBN 3-527-29589-5
    Publication Date: 2020-04-01
    Type: Book chapter , NonPeerReviewed
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