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Expression of intracellular ammonium assimilation enzymes were used to assess the response of nitrogen (N) metabolism in bacterioplankton to N-loading of sub-tropical coastal waters of Key West, Florida. Specific activities of glutamine synthetase (GS) and total glutamate dehydrogenase (GDHT) were measured on the bacterial size fraction (<0.8 μm) to assess N-deplete versus N-replete metabolic states, respectively. Enzyme results were compared to concentrations of dissolved organic matter and nutrients and to the biomass and production of phytoplankton and bacteria. Concentrations of dissolved inorganic N (DIN), dissolved organic N (DON), and dissolved organic carbon (DOC) positively correlated with specific activities of GDHT and negatively correlated with that of GS. Total dissolved N (TDN) concentration explained 81% of variance in bacterioplankton GDHT:GS activity ratio. The GDHT:GS ratio, TDN, DOC, and bacterial parameters decreased in magnitude along a tidally dynamic trophic gradient from north of Key West to south at the reef tract, which is consistent with the combined effects of localized coastal eutrophication and tidal exchange of seawater from the Southwest Florida Shelf and Florida Strait. The N-replete bacterioplankton north of Key West can regenerate ammonium which sustains primary production transported south to the reef. The range in GDHT:GS ratios was 5–30 times greater than that for commonly used indicators of planktonic eutrophication, which emphasizes the sensitivity of bacterioplankton N-metabolism to changes in N-bioavailability caused by nutrient pollution in sub-tropical coastal waters and utility of GDHT:GS ratio as an bioindicator of N-replete conditions. 相似文献
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M. Hoch 《Mineralogy and Petrology》1999,65(1-2):51-67
Summary Petrographic and geochemical data are presented for some ouachitites from the Schirmacher Oasis. The studied dike intruded into the metamorphic basement of the East Antarctic craton. The ouachitite samples contain substantial amounts of zoned phlogopite and diopsidic to salitic pyroxene as phenocrysts. K-rich nepheline is the predominant phase of the matrix. The rocks are characterized by low SiO2 concentrations (up to 36.5 wt.%), low mg# and high abundances of Al2O3, alkalis and volatiles. Trace element compositions of the Schirmacher ouachitites differ from those of ultramafic lamprophyres from other regions in that they contain significantly lower Cr and Ni concentrations and relatively low enrichments in LILE and LREE. The studied rocks have low143Nd/144Nd and enhanced87Sr/86Sr ratios. Pb isotope compositions of the ouachitites closely resemble those of MORB. The 18O values range between 4.1 and 4.70/00 which may be due to interactions with meteoric water. Because the Schirmacher ouachitites are only represented by a few samples it is impossible to discuss the petrogenesis of this magma. However, according to trace element and isotopic characteristics, it can be ruled out that Schirmacher ouachitites and associated minettes (documented inHoch, 1997;Hoch andTobschall, 1998) were derived from the same mantle reservoir.
With 6 Figures 相似文献
Geochemie und Petrologie von Ouachititen aus der Schirmacher Oase, Ostantarktika
Zusammenfassung In dieser Arbeit werden petrologische und geochemische Daten von Ouachititen aus der Schirmacher Oase vorgestellt. Der beprobte Gang intrudierte in das metamorphe Basement des ostantarktischen Kratons. Zonierte Phlogopite und diopsidische bis salitische Pyroxene sind die häufigsten mafischen Einsprenglinge. K-reiche Nepheline bilden die Hauptmineralphase der Grundmasse. Charakteristisch für die Ouachititproben sind niedrige SiO2-Konzentrationen (bis 36.5 Gew.%) und mg#, aber hohe Gehalte an Al2O3 Alkalien und volatilen Bestandteilen. Die Spurenelementzusammensetzung der Schirmacher Ouachitite unterscheidet sich von UML-Proben aus anderen Regionen durch ihre extrem geringen Cr- und Ni-Konzentrationen und die vergleichsweise niedrigen Anreicherungen an LILE und LREE. Die bearbeiteten Gesteine zeigen niedrige143Nd/144Nd- und erhöhte87Sr/86Sr-Verhältnisse. Die Pb-Isotopie der Ouachitite entspricht der von MORB. 6180-Werte variieren zwischen 4.1 und 4.70/00, was auf eine eventuelle Beeinflussung durch meteorische Wässer hindeutet. Da von den Schirmacher Ouachititen nur wenige Proben für eine Bearbeitung zur Verfügung standen, ist es nicht möglich, die Petrogenese des Magmas zu diskutieren. Aber aufgrund der Spurenelement- und Isotopensignaturen kann ein gemeinsames Mantelreservoir der Schirmacher Ouachitite und Minette (beschrieben inHoch, 1997;Hoch undTobschall, 1998) ausgeschlossen werden.
With 6 Figures 相似文献
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Dorman Clive E. Hoch Sebastian W. Gultepe Ismail Wang Qing Yamaguchi Ryan T. Fernando H. J. S. Krishnamurthy Raghavendra 《Boundary-Layer Meteorology》2021,181(2-3):171-202
Boundary-Layer Meteorology - The goal of this work is to summarize synoptic meteorological conditions during the Coastal Fog (C-FOG) field project that took place onshore and offshore of the Avalon... 相似文献
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Gultepe I. Heymsfield A. J. Fernando H. J. S. Pardyjak E. Dorman C. E. Wang Q. Creegan E. Hoch S. W. Flagg D. D. Yamaguchi R. Krishnamurthy R. Gaberšek S. Perrie W. Perelet A. Singh D. K. Chang R. Nagare B. Wagh S. Wang S. 《Boundary-Layer Meteorology》2021,181(2-3):227-265
Boundary-Layer Meteorology - Our goal is to provide an overview of the microphysical measurements made during the C-FOG (Toward Improving Coastal Fog Prediction) field project. In addition, we... 相似文献
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Calcium concentration and calcite supersaturation (Ω) needed for calcium carbonate nucleation and crystal growth in Pyramid
Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has Ω values of 10–16. Notwithstanding
high Ω, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months.
However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and
crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM (n = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean Ω at nucleation
(109 with a standard deviation of 8) is about eight times the PL surface-water Ω. Calcium concentration and Ω regulated the
calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower Ω than filtered
samples. Calcium concentration and Ω at nucleation for experiments in the presence of added particles were within one standard
deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate
(mM/min) = A (Ω) + B. The best fit rate equation “Rate (Δ mM/Δ min) = −0.0026 Ω + 0.0175 (r = 0.904, n = 10)” was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, Ω at zero
rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments
and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates
PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors. 相似文献
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Governments and development organisations consider the involvement of poor forest managers in global value chains and markets as a most promising approach for resolving the social and environmental challenges of the Amazon. This paper intends to provide a clearer picture about opportunities and potentials of this market-approach, by analysing integrated forest based development initiatives in the Bolivian, Brazilian, Ecuadorian and Peruvian Amazon. Findings suggest that the externally promoted initiatives seldom correspond to local realities and that they suffer from limited financial viability due to competitive disadvantages of locals in comparison to more capitalized actors. Success stories remain isolated without replication, and depend on external support for continuation. Only a limited number of families provided with privileged support have been able to overcome the technical, institutional and financial hurdles and to benefit from existing market opportunities. In some cases, interventions have generated conflicts and even weakened social organisation. Instead of simply copying the mistakes of the past regarding the emerging markets for environmental services, it is deemed essential to question the current market focus and search for alternatives placing greater emphasis on the interests, cultures and capacities of local people. 相似文献
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Perelet Alexei O. Gultepe Ismail Hoch Sebastian W. Pardyjak Eric R. 《Boundary-Layer Meteorology》2021,181(2-3):295-315
Boundary-Layer Meteorology - We investigate the path-averaged visibility and discrimination of fog and rain events using a two-wavelength (near-infrared and microwave) scintillometer system. These... 相似文献
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Gultepe I. Pardyjak E. Hoch S. W. Fernando H. J. S. Dorman C. Flagg D. D. Krishnamurthy R. Wang Q. Gaberšek S. Creegan E. Scantland N. Desjardins S. Heidinger A. Pavolonis M. Heymsfield A. J. 《Boundary-Layer Meteorology》2021,181(2-3):203-226
Boundary-Layer Meteorology - The objective of this work is to evaluate GOES-R (Geostationary Operational Environmental Satellites-R series) data-based fog conditions which occurred during the C-FOG... 相似文献