摘要:

AbstractIn the context of an extensive study of 101 Spanish reservoirs, we have explored the relationship between transparency (0.11 ≤ SD ≤ 8.6 m) and a number of general limnological parameters. Principal components analysis has been used as a means to summarize these relationships in two distinct periods, winter and summer, revealing the grouping of variables associated to abioseston or with biomass. Multiple regression analysis has been used to quantify these relationships. Total labile iron, calcium and chlorophyll appeared to be the best regressors of turbidity among our variables. The association between total labile iron and turbidity can be explained by the widespread adsorption of metals onto particles. Total labile manganese and phosphorus showed a similar behaviour, especially in winter. The presence of a relatively large proportion of detrital matter in low‐biomass eutrophic reservoirs in winter has been revealed by the analysis of Chla:C and Chla:N ratios. The fact that low ratios were associated with high iron concentrations gives support to this view. Also the C:P and N:P particulate atomic ratios differed from winter to summer. All these ratios appear to be very sensitive to the presence of a variable detrital component and, therefore, their use as indicators of the physiological state of phytoplanktonic populations is highly discouraged for these reser

ISSN:0020-9309    

DOI:10.1002/iroh.19950800102

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

摘要:

AbstractSaidenbach Reservoir is situated in the Erzgebirge Hills, Saxony, in a catchment with agriculture as the principal use and a high sensitivity to soil erosion. The high elimination of total phosphorus (ca. 70%) mainly results from a) the sedimentation flux of planktonic diatoms and b) the adsorption to and sedimentation with mineral particles rich in iron. At stations with a high sulfide concentration in the 0–5 cm sediment layer (about 0.2%), the P content was likewise high (about 0.3%), probably due to the high iron concentration (more than 2.5% of dry weight). A fractionation procedure showed that the major part of the sediment phosphorus was not sensitive to reductants (dithionite) but has been found only in the following extraction step (NaOH extract

ISSN:0020-9309    

DOI:10.1002/iroh.19950800103

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19950800104

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

摘要:

AbstractThe analysis of data, obtained in more than 400 hydrological surveys of 13 large and small reservoirs during 1960–1993, was made. It was established that the features of bed's form, the irregularity of the water exchange and the horizontal lability of water masses are the causes for the multi‐component hydrological structure of the valley reservoirs. The factors ought to be taken into account in modelling of aquatic ecosyst

ISSN:0020-9309    

DOI:10.1002/iroh.19950800105

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

摘要:

AbstractThe box‐model of the heat and mass transfer processes in the reservoir and the analysis of the model verification results on the basis of Mozhaliskoye Reservoir field observations data during 3 years are presente

ISSN:0020-9309    

DOI:10.1002/iroh.19950800106

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19950800107

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

摘要:

AbstractThe stratification of two shallow and small pools, situated in a floodplain ecosystem, was investigated.A new methodological approach was applied. The parameter called summarized chemical and biological stratification (SCB), was derived from basic limnological parameters in order to evaluate the global intensity of chemical and biological stratification and to compare it with a thermal one.Three situations were described when the seasonal courses of thermal and SCB stratification were compared: 1. Both SCB and thermal stratification are present. 2. The water column is homogeneous — there is no stratification in the pool. 3. SCB stratification is present, but the water is homoiothermic. The thermal stratification is very unstable because of the small volume of the pools and frequent floods. The SCB stratification is of higher stability and it may persist in a homoiothermic water column. In comparison with temperate deep lakes, the thermal stratification does not play such an important role in initiating the chemical and biological stratification. The surface/volume ratio and the depth in the pools are lower, which cause the “bottom‐initiated” quick renovation of stratification even in homoiothermic water.The differences in oxygen regime, volume and localization of both investigated pools cause the differences in stratification patterns. Frequent oxygen depletions in one of the pools increase the intensity of stratification and influence its character. The anaerobic conditions lead to steeper gradients of basic nutrients, pH, alkalinity and water color.The occurrence of a unique phytoplankton community (Cryptophyceae) is probably closely related to the described stratification p

ISSN:0020-9309    

DOI:10.1002/iroh.19950800108

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19950800109

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

摘要:

AbstractFeeding rates ofBrachionus plicatiliswere studied for two types of food — algaeMonochrysis lutheriand baker's yeastSaccharomyces cerevisae.The main regularities of changes in filtration rate and ration were studied in small culture volumes (1 ml) for adult amictic females depending on food concentration (1, 2, 4, 8 and 16 · 106cells · ml−1), ambient temperature (16 and 26 °C), and salinity (5, 10, 15, 20, 25 and 30 ppt).B. plicatilisration did not depend on the salinity, but was largely determined by temperature and food concentration. It was found that at 16 and 26 °C the dependence of the ingestion rate (ration) on food concentration differed greatly. A hypothesis was suggested to explain this phenomenon. A critical concentration of both types of food at which the increase in the rotifer ration ceased is 4 · 106cells · ml−1.This is the minimum “background” food concentration forB. plicatilismass cultivation.The average rations measured at the concentration ofM. lutheriandS. cerevisaeof 4 · 106cells · ml−1where 1.3 ± 0.1 and 4.8 ± 1.3 μg dry weight. · ind−1· day−1at 26 °C and 0.54 ± 0.1 and 1.9 μg d. w. · ind−1· day−1at 16 °C, respectively. The rations obtained in the laboratory were corrected for the conditions of rotifer commercial production in the open field in summer time. The correct values were 0.86 and 0.72 μg d. w. · ind

ISSN:0020-9309    

DOI:10.1002/iroh.19950800110

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19950800111

出版商:Akademie Verlag, Berlin    

年代:1995

数据来源: WILEY