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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 6 (1976), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A situation is described where silicon depletion affected a population of diatoms, mainly Diatoma elongatum and Melosira spp., in the shallow lake Tjeukemeer (The Netherlands). After Si-deficiency the numbers of cells dropped quickly, whereas at least for the upper layer (0–1 m) a big increase in the percentage of biprotoplastic D. elongatum cells was observed. Probably the major part of the D. elongatum population arrived alive at the bottom. Heavy winds occurring 2 weeks later stirred up considerable numbers of both diatoms. The numbers of dead D. elongatum cells was then 40–50%, presenting some evidence that a large scale dying of D. elongatum cells occurs rather shortly after arrival at the bottom of Tjeukemeer. In the following weeks, at low Si-concentration, numbers of D. elongatum almost doubled with once again a relatively high percentage of biprotoplastic cells, whereas numbers of Melosira spp. decreased. In the relevant conditions it seems that D. elongatum can take up silicon faster than Melosira spp.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 24 (1990), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1 The concentrations of total and dissolved (〈0.2 μm) Fe, Mn, Cu, Co, Zn and Al in the Dutch reservoir, the Tjeukemeer, were recorded fortnightly between 1984 and 1986.2 Due to its reservoir function, the Tjeukemeer receives water that is relatively rich in Fe and Mn from its peaty drainage area in winter. In summer, water that is relatively rich in Cu and Zn from lake IJsselmeer, which is flushed by a tributary of the River Rhine, flows into the lake. Therefore trace metal loads, as estimated from annual mean concentrations and hydraulic data, are climate-dependent.3 In wet years, such as 1985, the annual Fe, Mn, Cu and Zn loads may be 3.1,0.2,0.001 and 0.009 gm−2, respectively. In dry years, such as 1984 and 1986, the Fe and Mn loads may be less than one quarter while the Cu and Zn loads may double. Especially in wet years comparable Cu and Zn inputs occur by deposition.4 Despite the dependence of trace metal loads on the climate-dependent water regime. Principal Component Analysis indicated no strong relation between the total Cu, Co, Zn and Al concentrations in lake water and hydrological tracers such as Cl− and UV absorbance. Instead, wind speed appeared to be more strongly connected with the dynamics of these metals. Thus in the shallow Tjeukemeer, internal trace metal loading due to wind-induced resuspension starts to dominate the contributions of external loads to the total metal concentrations at wind speeds exceeding 3ms−1.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The small Lake Negenmad, in the nature reserve ‘De Oude Venen’, was isolated from the canals and lakes of the Frisian lake system. Its chemistry and phytoplankton were monitored 1 year before (1984) and 2 years after (1985–86) isolation. These characteristics were compared with those of the adjacent Lake Veertigmad which was not manipulated.2. The hydrological intervention prevented the inflow of chloride-rich IJsselmeer water into Lake Negenmad and made its water table more dependent on evapotranspiration, precipitation and upwelling water. In comparison with the unmanipulated lake. Lake Negenmad became less saline (c. 50%), more humic (c. 50%) and total dissolved (〈0.2,μm) iron concentration increased dramatically.3. During the 2 years of damming no marked differences in the total nutrient concentrations of either lake were observed. However, the maximum phytoplankton density in the dammed lake was half that in the unmanipulated lake. The lower density may have been caused by low P availability after formation of humus-iron phosphate species.4. Preventing the inflow of water from the Frisian lake system favoured the occurrence in Lake Negenmad of flagellated species (Chrysophyceae, Cryptophyceae) at the expense of filamentous and nuisance-causing cyanobacteria (Oscillutoria, Anabaena, Aphanizomenon spp.).5. The implications of these results for water quality management of reservoirs in peaty areas are briefly discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 5 (1975), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Diatoma elongatum has been observed in Tjeukemeer (The Netherlands) from time to time. Its intermittent presence is probably a consequence of the local hydrology. In early 1972, besides the usual increase of Melosira spp. and of unicellular centric diatoms, a development of D. elongatum took place. Its maximum was found 5-6 weeks later than those of the centric diatoms. Possible factors causing the decrease in number of cells are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 95 (1982), S. 223-234 
    ISSN: 1573-5117
    Keywords: algal periodicity ; Tjeukemeer ; diatoms ; blue-green algae ; green algae ; biovolume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal periodicity of algal numbers and biomass and of chlorophyll-a was investigated in the shallow, eutrophic, alkaline and peaty lake, Tjeukemeer, The Netherlands, during 1968–1978. Diatoms and Scenedesmus spp. were abundant throughout the whole period. Several blue-green algal species, occurring since 1971, usually dominated for most of the year. Relative abundance of algal species in Tjeukemeer during the study period were compared with that in 1955–1960.
    Type of Medium: Electronic Resource
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