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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 30 (1983), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Although mean size provides a useful value for characterizing sediments, it is an inadequate expression of the interaction between sediments and hydraulic regimes and many authors have explored the significance of other statistical moment measures in different parts of the particle size spectrum. Few publications, however, have described such relationships over a very wide range of particle sizes. Using a combined data base (of marine and lacustrine sediments) we have been able to demonstrate the following:The distributions of standard deviation (and entropy) values are repeated in similar form on either side of the sand size class, describing mixtures between sands and gravel and sands and clay.Skewness is modified by the hydraulic response of the sediment and a skewness divide is present at about 2.7 φ, where it coincides with the minimum shear velocity required to initiate particle motion. This divide may be used to distinguish between high and low energy regimes.Kurtosis, like standard deviation, is a measure of the mixing of end member populations but it is more sensitive to changes in the tails of distribution curves. The maximum positive peak of kurtosis, at about 2.5 φ, lies close to the skewness divide (in our data).By using skewness/kurtosis plots it is possible to define separate field distribution for sediments which, to a greater or lesser degree, appear to conform to hydraulic equilibrium.By using sediments which are close to equilibrium (and lie at or close to our skewness/kurtosis boundary curves, it should be possible to define hydraulic shear velocities, at the time of formation. Values may be established by empirical relationships or by defining the break-point (traction and intermittent suspension) between linear components of individual sample φ size/probability distribution plots. Such relationships should be enhanced by using hydraulic equivalent diameters instead of sieve diameters.In fine sediments, the use of fractional (silt: clay) ratios offers sensitivity at a level comparable to that of skewness/kurtosis plots and may be more easily computed.
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 204 (1964), S. 174-175 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Hecent work (unpublished) in the Harlech Dome has shown the structural pattern to be more complex than has previously been supposed; consequently certain of the methods used by Kopstein are now known to be inapplicable. He concluded that, with the exception of the Dolwen Grits, palseocurrent ...
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 91-92 (1982), S. 71-84 
    ISSN: 1573-5117
    Keywords: sediments ; lakes ; seas ; oceans ; energy relationships ; population statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sediments in the marine environment are generally subject to higher energy levels than those of lake systems, and lakes are virtually unaffected by tidal range which modifies beach structures formed in response to wave effects. However, despite different energy levels, the textural characteristics of both marine and lacustrine sediments are very similar. The main difference between marine and lacustrine facies is the depth range over which these characteristics remain consistent. In lakes, depth limitation may influence the development of surface waves and restrict textural distributions. Simple textural relationships can be used to describe comparable marine and lacustrine sedimentary conditions. Sediments which have been altered by post-depositional erosion, such as lag deposits, or by ice-drop or wind blown settlement, show comparable textural modifications. The settlement of silt and clay size particulates, in the marine environment and lakes, may differ slightly because of the chemical differences between salt and fresh water.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 91-92 (1982), S. 1-8 
    ISSN: 1573-5117
    Keywords: symposium ; sediments ; freshwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 91-92 (1982), S. 71-84 
    ISSN: 1573-5117
    Keywords: sediments ; lakes ; seas ; oceans ; energy relationships ; population statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sediments in the marine environment are generally subject to higher energy levels than those of lake systems, and lakes are virtually unaffected by tidal range which modifies beach structures formed in response to wave effects. However, despite different energy levels, the textural characteristics of both marine and lacustrine sediments are very similar. The main difference between marine and lacustrine facies is the depth range over which these characteristics remain consistent. In lakes, depth limitation may influence the development of surface waves and restrict textural distributions. Simple textural relationships can be used to describe comparable marine and lacustrine sedimentary conditions. Sediments which have been altered by post-depositional erosion, such as lag deposits, or by ice-drop or wind blown settlement, show comparable textural modifications. The settlement of silt and clay size particulates, in the marine environment and lakes, may differ slightly because of the chemical differences between salt and fresh water.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 91-92 (1982), S. 1-1 
    ISSN: 1573-5117
    Keywords: symposium ; sediments ; freshwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of aquatic ecosystem stress and recovery 5 (1996), S. 153-175 
    ISSN: 1573-5141
    Keywords: lake trout ; spawning habitat ; Great Lakes basin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We provide further insight into the reproductive ecology and spawning requirements of lake trout. New comparative information about substrate characteristics, sediment transport, quality of interstitial water at spawning substrates, and the role of temperature in site selection and time of spawning is given for lakes Simcoe and Manitou (Ontario) and Seneca Lake (New York). Spawning lake trout commonly use stable lag deposits derived from glacial sediments, or relict features such as fans, bars or submerged talus slopes. Artificial breakwaters of broken material may also provide suitable substrates. Optimal particle sizes range from 4 to 10 cm diameter but larger materials to 30 cm are also successfully utilized for spawning. The transport of finer particulates by wind generated water movements may limit the suitability of some substrates and successful spawning sites are usually remote from depositional effects. Successful embryo development is associated with low nutrient conditions, with high dissolved oxygen (〉7 mg L-1) and with low un-ionized ammonia (〈12.5 μg L-1) in the interstitial water of spawning substrates. Shallow-water spawning appears to be the common strategy of colonizing lake trout. Some deepwater spawning in the Great Lakes may reflect initial colonization in shallow-water and adaptation to later increases in water level, but some may also reflect unique behavioural and physiological adaptations. Temperature is an important cue, and many wild and hatchery stocks spawn at 8 to 13 °C with latitudinal shifts in the actual time of spawning. These requirements are summarized as a dichotomous key for evaluation of approaches to restoration of lost or damaged lake trout stocks.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 213 (1991), S. 1-75 
    ISSN: 1573-5117
    Keywords: Lake Ontario ; cultural development ; environmental impacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ontario is the lowest in the chain of five Great Lakes which form part of the boundary between Canada and the United States. Although European exploration began as early as 1615, it was not until the mid-18th Century that permanent settlement began in the Great Lakes basin. Construction of the Erie Canal which links Buffalo with New York via the Hudson River, and its branch to Oswego, strengthened ties between settlements around the lower Great Lakes (lakes Erie and Ontario) and rapidly growing populations along the Atlantic seaboard. The coming of railroads greatly expanded these ties, and provided a direct link between Canadian settlements and the port of Montreal. Over the past 200 years, successive waves of immigrants entered the region, particularly from Europe. Cultural development has resulted in a wide range of environmental impacts throughout the Great Lakes basin. Impacts have been particularly severe in Lake Ontario. Major changes in water quality and the structure of biological communities have resulted from forest clearance, agricultural expansion, intensive fishing, industrial and urban development, and lake level control. Introductions of exotic species, inputs of nutrient and toxic contaminants, and the effects of climatic variation and modification of microclimates have all interacted such that it is often impossible to establish singular cause and effect. The effects of cultural impact became most severe during the early 1970s and prompted strong support for the International Great Lakes Water Quality Agreement (1972) between Canada and the United States. In response to this agreement and subsequent revisions, contaminant loadings have been greatly reduced. Present water quality is generally good in Lake Ontario although some persistent toxic substances remain a problem. Programs to restock the lake have also provided major benefits. Although much further work remains, Lake Ontario is undoubtedly a good example of successful large scale remedial actions.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 235-236 (1992), S. 321-352 
    ISSN: 1573-5117
    Keywords: Pontoporeia hoyi ; sediment-water interface ; organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physical and chemical characteristics of the sediment-water interface greatly influence distributions of the bottom-feeding amphipod Pontoporeia hoyi which is a major component of the Great Lakes aquatic food-webs. Sediment-water interface samples from the Great Lakes indicate that Pontoporeia densities are positively correlated with sediment concentrations of organic carbon, particularly in the upper depth range of the species. Pontoporeia is not found in anoxic sediments. Growth rates and production of Pontoporeia are influenced by the quality of food supplies and there appears to be a seasonal response to the down-flux of plankton detritus. Comparisons of numerations and distribution patterns also revealed an apparent positive relationship between Pontoporeia and sediment-associated bacteria. Interlake comparisons of population densities provide no clear evidence of any large scale impact by contaminated sediment on this species. Depending upon the extent to which organic carbon (OC) is assimilated in the water column, bottom sediments may store and buffer the quantity of OC available to Pontoporeia. Thus, if the annual down-flux of OC remains generally constant, populations of Pontoporeia should also remain constant unless influenced by changes in predation intensity. Numerations of Pontoporeia revealed that populations of this amphipod are much larger in Lake Michigan than in Lake Ontario. We suggest that much of this difference can be accounted for by different forms of predator-prey interaction near the base of the benthic food-web. Commercial fisheries data tend to support this idea. We also speculate that differences in the concentration of dissolved silica may figure prominantly among factors that affect Pontoporeia population densities.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 268 (1993), S. 193-193 
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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