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  • 1
    Digitale Medien
    Digitale Medien
    Multivariate Analysis of Protist Communities in Lentic Systems (1986)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 33 (1986), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . The purpose of this research was to examine the roles of physico-chemical parameters in structuring protist communities that colonize artificial substrates. Polyurethane foam (PF) substrates were placed in five lentic systems in northern lower Michigan during summer 1983. These lentic habitats represented a range of trophic states and included three lakes, a bog, and a marsh. Triplicate PF substrates were sampled after 1, 3, 7, 14, 21, and 42 days of exposure. During this study, 90 living protist samples were examined for the number and kinds of species. Water samples were analyzed for pH, conductivity, alkalinity, chloride, silica, temperature, dissolved oxygen, ammonia, and total and ortho-phosphate concurrent with artificial substrate collections. A total of 546 protist species was recorded. Only seven species were found in over 50% of the samples and 121 species were found in only one sample. The 96 most common species were examined in relation to environmental parameters using several multivariate statistical procedures. Factor analysis (principal components with varimax rotation) performed on the total environmental data set showed that three composite factors explained 85% of the variability of the data set. A reciprocal averaging ordination (RAO) was used to reduce species presence/absence data and to separate samples graphically by their species composition. Significant correlations, with RAO-generated axes from all five systems, were found for pH, oxygen, and a nutrient factor to axis 1. Factor analysis on the physico-chemical parameters of the three lakes showed that three factors explained 71% of the environmental data set variability. The RAO-generated axis (axis 1) was correlated with silica, ortho-phosphate, and Factor 2, which was primarily comprised of loadings from ortho-phosphate. These techniques support the hypothesis that a limited number of environmental parameters strongly affect protist community composition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1986.tb05581.x
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  • 2
    Digitale Medien
    Digitale Medien
    Regulation of c-fos Messenger Ribonucleic Acid by Fibroblast Growth Factor in Cultured Sertoli Cells (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 564 (1989), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1989.tb25893.x
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  • 3
    Digitale Medien
    Digitale Medien
    An assessment methodology for successional systems. II. Statistical tests and specific examples (1990)
    Springer
    Environmental management 14 (1990), S. 259-268 
    Details
    ISSN: 1432-1009
    Schlagwort(e): Monitoring ; Statistical analysis ; Null models ; Stochastic models ; Hypothesis testing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract This paper presents a dynamic framework for environmental assessment when the system under study is undergoing successional change. Successional differences between sites for which one wishes to detect a difference because of a treatment are essentially confounding factors. We show how successional changes over the study period or resulting from differences in study site plot ages can be factored out by developing a null model of expected behavior over time. The null model for change in state with time is characterized in terms of a stochastic envelope around a nominal trajectory. Specific tests for the detection of trends associated with succession are described and illustrated on example data. It is concluded that the methods developed work particularly well for laboratory microcosm data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02394043
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  • 4
    Digitale Medien
    Digitale Medien
    UIT observations of NGC 1275 (1993)
    Springer
    Astrophysics and space science 205 (1993), S. 65-68 
    Details
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present the results from UV imagery of NGC 1275 obtained using the Goddard Ultraviolet Imaging Telescope (UIT). We are able to study the UV morphology down toµ249 ~ 25 mag arcsec−2. There are significant non-axisymmetric structures in the UV continuum associated with the low-velocity filament system. Continuum from the high-velocity system may also be present. The large aperture UV colors indicate that although the mass function extends to ~5M ⊙ , more massive objects are not present. This implies either a cessation of star formation during the last 50–100 Myr or a truncated initial mass function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657958
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  • 5
    Digitale Medien
    Digitale Medien
    The relative importance of population versus community processes in microbial primary succession (1991)
    Springer
    Hydrobiologia 213 (1991), S. 83-98 
    Details
    ISSN: 1573-5117
    Schlagwort(e): succession ; protists ; competition ; facilitation ; dispersal ; individualistic hypothesis ; community-unit hypothesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Interpretations of successional patterns in ecological communities have traditionally adhered to the dichotomy between the Clementsian view that emphasizes community level processes and the Gleasonian view that stresses individual population responses. The present study evaluates the relative importance of each type of process during protistan primary succession in initially barren aquatic isolates (200-1 plastic pools) over a 170-d period. Species availability to these systems was manipulated by erecting exclosures around individual mesocosms to successively eliminate access to different dispersal vectors responsible for passive protistan dispersal. Increased exclosure significantly reduced access of autotrophs to the pools, but had little effect on heterotroph species availability. The species replacement process was directional through time and occurred at similar rates in all treatments. Both lower and upper temporal boundaries of heterotrophic and autotrophic species were contagious through time, as predicted by the Clementsian hypothesis, although the independence of these two boundary types suggested an individualistic model. Dominant and subdominant species were correlated into four temporal groups: pioneer, early successional, mid-successional, late successional. The dominance of several mid- and late successional species was reduced with increased exclosure. The loss of these species from successional pathways in more exclosed pools had no significant effect on the distribution of other species within the same temporal group. However, the establishment of these other mid- and late successional species may be dependent on initial colonization by pioneer and early successional species. Increased abundances of mid- and late successional species in less exclosed pools coincided with significant attenuations in the distribution of many early successional species. Interactions between successional groups may be related to the supply of inorganic resources as well as allelopathic effects. Patterns of protist succession are the result of both population and community processes; while species-specific characteristics (i.e., dispersal ability) may dominate the process in more isolated systems, increased species availability increases the relative importance of interspecific interactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014995
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  • 6
    Digitale Medien
    Digitale Medien
    Developing a statistical support system for environmental hazard evaluation (1989)
    Springer
    Hydrobiologia 184 (1989), S. 143-151 
    Details
    ISSN: 1573-5117
    Schlagwort(e): validation ; risk assessment ; microcosms ; toxicity tests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Estimating the hazard or risk to both human health and the environment has been based almost exclusively on single species toxicity tests low in environmental realism and without validation of their accuracy in more complex systems. While this may be quite appropriate for humans in a large variety of circumstances, there is no substantive body of direct experimental evidence indicating that precise predictions of harm from hazardous materials can be extrapolated from single species laboratory tests (or even multispecies laboratory tests) to the more complex highly variable natural systems. Now added to the hazardous chemical assessment problem is the accidental or deliberate release of genetically engineered microorganisms into the environment that have the additional capability of multiplying and expanding their numbers and also transferring genetic information to other organisms. This paper focuses entirely on hazard evaluation for organisms other than humans, namely predicting the potential risk or probability of harm to natural systems based on laboratory toxicity testing using single species. Not only will the basic risk assessment strategy itself be examined but also the question of determining the statistical reliability of various extrapolations from one level of biological organization to another. ‘For every complex problem, there is a simple, direct solution ... and it is invariably wrong!’ H. L. Mencken
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00027022
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  • 7
    Digitale Medien
    Digitale Medien
    Developing a statistical support system for environmental hazard evaluation (1989)
    Springer
    Hydrobiologia 184 (1989), S. 143-151 
    Details
    ISSN: 1573-5117
    Schlagwort(e): validation ; risk assessment ; microcosms ; toxicity tests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Estimating the hazard or risk to both human health and the environment has been based almost exclusively on single species toxicity tests low in environmental realism and without validation of their accuracy in more complex systems. While this may be quite appropriate for humans in a large variety of circumstances, there is no substantive body of direct experimental evidence indicating that precise predictions of harm from hazardous materials can be extrapolated from single species laboratory tests (or even multispecies laboratory tests) to the more complex highly variable natural systems. Now added to the hazardous chemical assessment problem is the accidental or deliberate release of genetically engineered microorganisms into the environment that have the additional capability of multiplying and expanding their numbers and also transferring genetic information to other organisms. This paper focuses entirely on hazard evaluation for organisms other than humans, namely predicting the potential risk or probability of harm to natural systems based on laboratory toxicity testing using single species. Not only will the basic risk assessment strategy itself be examined but also the question of determining the statistical reliability of various extrapolations from one level of biological organization to another. ‘For every complex problem, there is a simple, direct solution ... and it is invariably wrong!’ H. L. Mencken
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02392950
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  • 8
    Digitale Medien
    Digitale Medien
    Similarities between rarefaction methods (1985)
    Springer
    Hydrobiologia 120 (1985), S. 167-170 
    Details
    ISSN: 1573-5117
    Schlagwort(e): species richness ; negative binominal ; quadrant sampling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The number of species in a community is one of the most commonly used measures of diversity. This measure is, however, affected by sample size. The rarefaction method attempts to correct sample size bias by assuming an underlying sampling model. Several rarefaction models are shown to be similar analytically. This similarity holds not only for the expected number of species but also for the variance of the number of species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00032138
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  • 9
    Digitale Medien
    Digitale Medien
    Confidence intervals for the similarity between algal communities (1986)
    Springer
    Hydrobiologia 139 (1986), S. 237-245 
    Details
    ISSN: 1573-5117
    Schlagwort(e): similarity ; SIMI ; confidence intervals ; jackknife ; bootstrap ; algae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract While researchers commonly use similarity measures to compare algal communities, very few researchers have considered the variability of these estimated measures. This paper discusses a recent method for estimating the variance of and confidence intervals for similarity measures proposed by Johnson & Millie (1982, Hydrobiologia 89: 3–8). Applications of this method to data have produced confidence intervals that are too narrow. Two alternative methods, the jackknife method and the bootstrap, are shown to provide superior estimates of the variability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028294
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  • 10
    Digitale Medien
    Digitale Medien
    Estimating the reliability of diet overlap measures (1985)
    Springer
    Environmental biology of fishes 13 (1985), S. 125-138 
    Details
    ISSN: 1573-5133
    Schlagwort(e): Sampling ; Nonparametric ; Jackknife ; Bootstrap ; Niche ; Competition ; Fishes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Diet overlap measures, commonly used in studies of resource partitioning and competition in fish, are too often treated as fixed values; in fact, they are random variables. Two methods for estimating the variance of some overlap measures using stomach content data are examined here: the jackknife and the bootstrap. Simulation results indicate that the methods work well. In addition, they are valid for either continuous (biomass, percent volume) or discrete (abundance) data. Applications indicate that outliers, such as a stomach much different than others, may have large influence in determing the overlap value.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00002581
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