摘要:

AbstractThe underwater light field is described as a stochastic process, with the vertical attenuation as a random variable. It is shown that the vertical attenuation integral is well described as a Normal process with uncorrelated increments. The attenuation processes within a water body are found to be quite independent of the incoming irradiance. Thus, the relative light intensity at any depth can be approximated by a Lognormal random variable. Based upon the expectation of this Lognormal variable, and the mean value of the incident irradiance, the irradiance delivered at any depth can be estimated, as well as the statistical distribution of the irradiance.Light data from a number of Norwegian soft‐water lakes showed good fit to the model. Two productive lakes included in this study also had a light regime well described by the statistical model. However, the model should be extended to cater for seasonal variations in these application

ISSN:0020-9309    

DOI:10.1002/iroh.19870720102

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19870720103

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper reports the effects of phosphorus removal at three sewage wastewater treatment plants on the state of eutrophication of four shallow lakes in the south‐eastern part of the Rijnland Waterboard area during the years 1980–1982. With chemical analyses and bioassay experiments using the natural phytoplankton population no significant lowering could be detected of respectively the phosphate concentration and the maximal algal growth potential. All lakes proved to be principally nitrogen limited except the Reeuwijk Lakes, which showed clearly, after a primary nitrogen limitation, a secondary phosphorus limitation. Therefore the main attention with respect to phosphorus reduction should be concentrated on the Reeuwijk Lakes in the first place. For the other lakes in the investigated area phosphorus removal will, when it is the only measure taken, presumably not lead at short notice to a decrease of the algal biom

ISSN:0020-9309    

DOI:10.1002/iroh.19870720104

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19870720105

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

摘要:

AbstractMost of the tested water quality factors increase downstream coinciding with changes in the aquatic vegetation, from typical species of fast‐flowing oligotrophic waters to those of slower‐flowing eutrophic waters. Several statistic analyses were carried out to relate physical and chemical parameters with plant distribution. Five vegetation types are found in a longitudinal distribution along the river system. They are dominated by bryophytes in the initial parts before the reservoirs and by higher plants in the final parts after the reservo

ISSN:0020-9309    

DOI:10.1002/iroh.19870720106

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

摘要:

AbstractIn the temperature range of 10 to 35°C the relationships of the oxygen consumption and nitrogen excretion rates to temperature inBrachionus calyciflorusPALLAS can be described by an exponential function whereQ10is equal to 2.45 or 2.18, respectively. Temperature adaptation within the range studied resulted in stabilisation of relative protein metabolism which accounted for nearly 50 per cent of the total metabolic loss

ISSN:0020-9309    

DOI:10.1002/iroh.19870720107

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19870720108

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

摘要:

AbstractSeasonal variation in population density, birth rate, mortality and production of a daphnid was studied in a high, altitude sub‐tropical lake. A bimodal growth curve with maxima during summer and autumn was observed. A positive correlation was reported between fecundity and death rate, probably due to a difference in age specific death rate combined with a high relative frequency of juveniles in a growing population. The production ofDaphnia longispinacorrelates better with temperature than with food. TheP/Bratio was higher during summer and autumn month

ISSN:0020-9309    

DOI:10.1002/iroh.19870720109

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

摘要:

Fatty Acid Composition of Lacustrian Phytoplankton (Pavin Lake, France)Fatty acid composition of lacustrian phytoplankton was established during a study carried out on Lake Pavin (France) from May to September 1981.Fatty acid spectra point out even numbers of carbon atoms (ranging from 14 to 22) and in particular unsaturated fatty acids preponderance. In addition, the occurrence of some unsaturated fatty acids is directly linked to phytoplankton taxonomic composition, but also to physiological state of the cells. Lastly, the main types of phytoplankton populations differ in the degree of unsaturation of their total fatty acids.

ISSN:0020-9309    

DOI:10.1002/iroh.19870720110

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19870720111

出版商:Akademie Verlag, Berlin    

年代:1987

数据来源: WILEY