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  • 1
    Electronic Resource
    Electronic Resource
    Are Recent Watershed Disturbances Associated with Temporal and Spatial Changes in Water Quality of Lake George, New York, USA? (1997)
    Springer
    Environmental management 21 (1997), S. 725-732 
    Details
    ISSN: 1432-1009
    Keywords: KEY WORDS: Repeated-measures ANOVA; Split-plot design; Lakewater chemistry; Lake George
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: a (Chl a), silica (Si), and chloride (Cl) through the use of proper statistical techniques. Results indicate no statistically significant changes in the concentrations of TP, Chl a, or Si in the spring or summer from 1981 to 1993. A significant temporal trend of increase in Cl concentration is, however, detected. This is perhaps the strongest evidence that the development of the Lake George watershed has affected lakewater chemistry. In spring, the concentrations of TP, Chl a, Si, and Cl, averaged over all 13 years, were higher in the south basin, but differences are not statistically significant (i.e., P 〉 0.05). In summer, Si was slightly but significantly lower, and Cl was nonsignificantly higher in the south basin. Significant interactions between temporal and spatial changes are detected based only on summer values of TP and Chl a, indicating differential trends of change for these two variables in the south and north basins during the last 13 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002679900062
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of nitrogen-fixation by different nitrogen sources in the marine non-heterocystous cyanobacterium Trichodesmium sp. NIBB1067 (1991)
    Springer
    Archives of microbiology 156 (1991), S. 335-337 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacterium ; Trichodesmium ; Nitrogen-fixation ; Nitrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of various nitrogen sources on the synthesis and activity of nitrogenase was studied in the marine, non-heterocystous cyanobacterium Trichodesmium sp. NIBB1067 grown under defined culture conditions. Cells grown with N2 as the sole inorganic nitrogen source showed light-dependent nitrogenase activity (acetylene reduction). Nitrogenase activity in cells grown on N2 was not suppressed after 7 h incubation with 2 mM NaNO3 or 0.02 mM NH4Cl. However, after 3 h of exposure to 0.5 mM of urea, nitrogenase was inactivated. Cells grown in medium containing 2 mM NaNO3, 0.5 mM urea or 0.02 mM NH4Cl completely lacked the ability to reduce acetylene. Western immunoblots tested with polyclonal antisera against the Fe-protein and the Mo−Fe protein, revealed the following: (1) both the Fe-protein and the Mo−Fe protein were synthesized in cells grown with N2 as well as in cells grown with NaNO3 or low concentration of NH4Cl; (2) two bands (apparent molecular mass of 38 000 and 40 000) which cross-reacted with the antiserum to the Fe-protein, were found in nitrogen-fixing cells; (3) only one protein band, corresponding to the high molecular mass form of the Fe-protein, was found in cells grown with NaNO3 or low concentration of NH4Cl; (4) neither the Fe-protein nor the Mo−Fe protein was found in cells grown with urea; (5) the apparent molecular mass of the Fe-protein of Trichodesmium sp. NIBB1067 was about 5000 dalton higher than that of the heterocystous cyanobacterium, Anabaena cylindrica IAM-M1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248706
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  • 3
    Electronic Resource
    Electronic Resource
    Expression of photosynthesis genes in relation to nitrogen fixation in the diazotrophic filamentous nonheterocystous cyanobacterium Trichodesmium sp. IMS 101 (1999)
    Springer
    Plant molecular biology 41 (1999), S. 89-104 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; circadian rhythm ; psaA ; psbA ; Trichodesmium sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The daily cycle of nitrogenase expression in the marine filamentous nonheterocystous cyanobacterium Trichodesmium spp. is controlled by a circadian rhythm. We evaluated the rhythm of two key photosynthesis genes, psbA of photosystem II and psaA of photosystem I, in Trichodesmium sp. IMS 101 using the 3 criteria for an endogenous rhythm. The transcript abundance of psbA and psaA transcripts oscillated with a period of ca. 24 h under a 12 h light/12 h dark regime. At 24 °C and 28 °C the cyclic pattern of transcript abundance was maintained for at least 58 h under constant light conditions, whereas the periods were about 24 h at 24 °C, and 26–30 h at the higher temperature. The cycles of psbA and psaA gene expression were entrained using light-dark cues. Transcription of nifHDK was initiated prior to the light period, followed by psbA and finally psaA. There was a 90° (6 h) phase difference between the net accumulation of nifHDK and psbA transcripts, as well as between that of psbA and psaA transcripts. Results of inhibitor experiments indicated that psbA and psaA transcription was regulated differently by initiation and degradation during the light period. Short-term changes of light conditions resulted in significant effects on psbA transcription and nitrogenase activity, but had less of an effect on psaA and nifHDK transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006231805030
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  • 4
    Electronic Resource
    Electronic Resource
    Determinants of Summer Nitrate Concentration in a Set of Adirondack Lakes, New York (1999)
    Springer
    Water, air & soil pollution 111 (1999), S. 19-28 
    Details
    ISSN: 1573-2932
    Keywords: Adirondack region ; canonical discriminant analysis ; cluster analysis ; lake nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Following reductions in the emission and deposition of sulfur compounds in the past decade, atmospheric deposition of nitrogen has become a focus of concern. Identification of watershed characteristics that mediate the effect of atmospheric nitrogen deposition can help evaluate the sensitivity of lakes to chronic and episodic nitrogen addition. Twenty four lakes in the southwestern portion of the Adirondack Park, New York, U.S.A., were classified into three N classes by cluster analysis of lakewater NO3- N concentration [N] during the summers of 1994–1996. The lake-N classes were best characterized as having (1) low [N] throughout the summer, (2) high [N] in early- but low [N] in late-summer, and (3) high [N] throughout the summer. The three lake-N classes were reconstructed perfectly by canonical discriminant analysis based mainly on lake average depth (AD), and lakewater concentrations of chlorophyll a [Chla] and SO4-S [S] in mid-summer. Increases in AD and [S], but decrease in [Chla] corresponded with a transition from low- to high-N classes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005006108629
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