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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic sciences 51 (1989), S. 1-1 
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic sciences 51 (1989), S. 19-30 
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A succession of fine dark and light laminations, covering a time span of ca 6,000 years (Allerød to Atlantic), was observed in the sediment of Soppensee, Central Switzerland. These laminations, consisting of dark, organic and diatom-rich winter/spring layers and light calcite summer layers, are shown to be varves by means of several independent pollen and diatom analyses, as well as thin-section studies of the sediment micro-structure.
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  • 3
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A simple model of the dynamics of a bubble plume is incorporated in the one dimensional model of reservoir dynamics DYRESM and tested against a data set from Myponga Reservoir in South Australia. The comparisons show that the model provides a reasonably good simulation of the dynamics, and allows use of the combined model for determining the behaviour of aerators under a number of operational strategies. It is shown that a peak efficiency in excess of 15% may be achieved from a single bubble plume, and that the total efficiency of an aerator operating with a fixed airflow rate and fixed configuration over a full season may be increased markedly from 1.5% to about 5.5% by a simple control method. It is suggested that total efficiencies of the order of 15% may be achieved by more complex control strategies.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present a fine vertical distribution of physico-chemical parameters and phytoplankton density around the halocline (freshwater/seawater interface) in the Krka estuary on the East coast of the Adriatic Sea. Suspended matter, surfactant activity, surface active aggregates, particulate organic carbon and phaeophytin all show largest concentrations in the 20–50 cm thick interface layer. The highest concentration of chlorophyll-a is found on the upper boundary of the interface and it is a consequence of majority of viable freshwater phytoplankton cells that accumulate there. The phytoplankton accumulates selectively in the interface: larger size fractions accumulate faster than smaller ones. In particular, nanoplanakton accumulates the least. The visible interface is also populated by dead phytoplankton cells. Most of the freshwater phytoplankton dies and decomposes in the interface, as revealed by a small chlorophyll-a/phaeophytin ratio, and it represents the main source of surface active dissolved and particulate organic matter. Marine flagellates migrate and divide in the interface, while some species likeProrocentrum micans andSyracosphera sp. are also found in the upper freshwater layer.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of the phytoplankton spring bloom in Lake Zürich in 1983 was investigated using frequent sampling with short sampling intervals, which allowed the influence of short-term meteorological events on the bloom to be studied. The bloom can be divided into four distinct growth periods (March 1–April 28) and a period of collapse (April 29–May 16). During the four growth periods, growth pulses were found to be associated with high solar radiation, little wind and a shallow mixed layer, whereas stagnation or loss was associated with strong winds and a consequent deepening of the mixed layer, resulting in an unfavourable effective light climate. The population collapse was brought about by zooplankton grazing, possibly coupled with nutrient limitation and other factors.
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  • 6
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The presence of unknown bacteria upon filaments of the CyanophyteOscillatoria rubescens was observed in the Lake Leman (Lake of Geneva) during Autumn 1985. Conditions of this colonization and the morphology of the association are described. These bacteria probably belong to theCaulobacter group. To explain this colonization we suggest that bacteria respond chemotactically to Cyanophyte exudates.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic sciences 51 (1989), S. 84-85 
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1420-9055
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Whitefish larvae (Coregonus sp.) were caught at regular intervals in 1986 and 1987 in oligotrophic Lake Sarnen, and in 1987 in eutrophic Lake Hallwil. The food spectra of the larvae in each lake were directly related to the available prey organisms. The causes for the important decrease of the larval catches in Lake Sarnen observed in 1987 are examined. There was no significant difference in the abundance and size distribution of the principal zooplankton taxa between the 1986 and 1987 samples. The effects of a sudden cooling of the surface water layer on the survival of cold-bred whitefish larvae are discussed.
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  • 9
    ISSN: 1420-9055
    Keywords: Unionidae ; life history ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Species composition, relative abundance and life history of unionid mussels are compared between 1982–86 and 1915–19 in Lake Hallwil and the outflowing brook. The recent samples of unionid mussels were collected by divers, whereas the older ones were from a shell collection. The motivation for the comparison was that the trophic degree of the lake has changed since the beginning of the century from mesotrophic to highly eutrophic. The effects of this increased trophic degree of the lake on the life cycle of unionid mussels is discussed. Predictions are made about species composition and life history in the context of the ongoing lake restoration by the authorities.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic sciences 51 (1989), S. 100-107 
    ISSN: 1420-9055
    Keywords: Perch ; reproduction ; fitness ; transplant experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Egg survival and development rate of perch eggs were investigated in Lake Zürich, Switzerland. A transplant experiment was carried out to examine whether individual females choose different depths for spawning because of an expected advantage for the development of their eggs. Egg masses which had been deposited on fir branches stuck into the ground of the lake were either left untouched or transplanted horizontally or vertically at depths of 3 and 6 m. Spawning occurred between 28 April and 9 June 1987. Egg survival to the eye pigment stage (EPS) was high in all treatments ( $$\bar x = 99\% $$ , minimum 92%). There was no significant difference in egg survival between treatments, suggesting that females do not choose the spawning site because of individual fitness differences related to the depth of spawning. Early egg masses which were exposed to lower temperatures developed more slowly (120–140 day degrees to the EPS) than late egg masses which were exposed to higher temperatures (80–100 day degrees). The observed differences are in agreement with the hypothesis of a constant sum of day degrees necessary for egg development using the corrected formula derived by Guma'a (1978) which deducts an estimated threshold temperature of 5°C below which development of perch eggs effectively stops, from the actual temperature.
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