摘要:

AbstractA two‐year study on the seasonal pattern of plankton was performed in a shallow, polymictic, eutrophic lake.Autogenic successions typical of stratified lakes did not occur. Only small edible algae developed throughout the two years and Cyanophyceae rarely appeared, and did not bloom. Algal sequences depended on wind‐induced periodic mixing of water.The seasonal pattern of Rotifers varied greatly from year to year and some species depended on sporadic increases of algae. In contrast, the seasonal pattern of microcrustacea was more regular. Resting stages played an important role in zooplankton development in this variable environment.Successful fish reproduction depended a great deal on climatic conditions. The changes from year to year in predation pressure from young fish appeared to be an important factor controlling zoo‐plankton stru

ISSN:0020-9309    

DOI:10.1002/iroh.19890740402

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

摘要:

AbstractAt a fixed station in the northern North Sea the occurrence of herbivorous and omnivorous zooplankton and the changes in its vertical distribution were studied over 2 1/2 months during the spring phytoplankton bloom in 1976.From a sporadical distribution of relative few plankton organisms in the mixed water column at the end of winter, in the middle of April a significant accumulation of organisms began to occur in the upper layers parallel to the development of stratification and the phytoplankton spring bloom. As exceptions, the populations ofMicrocalanus pusillusandMetridia lucenswithdrew to below the thermocline.About ten days after the decline of the phytoplankton bloom, a few zooplankton species—especially wax ester producing copepods likeCalanus finmarchicus, Pseudocalanus elongatus, Microcalanus pusillus, aad Metridia lucens—started diurnal vertical migrations. The movements of the species and stages occurred synchronously, leading in the same direction. Nevertheless, the amplitude of the migrations increased with each maturity stage reached.The vertical migrations, characterized by actual locations and velocities of the centers of gravity of the populations, are interpreted in terms of metabolism leading to fat storage, decomposition and reconstruction of lipids and proteins, in terms of a periodical change in the density of the organisms.Further data sets about the vertical distribution of organisms are cited to support the hypotheses sta

ISSN:0020-9309    

DOI:10.1002/iroh.19890740403

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

摘要:

AbstractSeasonal variations in some physical and chemical characteristics of samples collected from summer 1984 to spring 1985 and vertically from the surface to the bottom at two sites along the main body of Aswan High Dam Lake and in two side Khors were studied. Water temperature showed seasonal as well as vertical variations. The pH values were in the vicinity of 8.0. Dissolved oxygen concentrations were higher at the surface than at the bottom. The total dissolved solids showed seasonal as well as irregular vertical variations. Bicarbonates, nitrates, and silicates showed a marked increase with depth, while sodium, potassium, calcium and magnesium showed generally a slight or, sometimes, marked increase with depth. Phosphates and sulfates showed a slight or marked decrease with depth. Chlorophyll a decreased with depth while bacteriochlorophyllaincreased.

ISSN:0020-9309    

DOI:10.1002/iroh.19890740404

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

摘要:

AbstractThe frequency of occurrence and seasonal periodicity of aquatic hyphomycetes in a temperate freshwater stream of Central Himalaya were studied. The number of aquatic hyphomycetes species was found to vary inversely with temperature (r= −0.499; not significant), which explained 25 % of the variability. There were two maxima, one in spring and the other in autumn. On the basis of their occurrence, the species observed have been categorised into three groups. Constant species wereCampylospora chaetocladia, Flagellospora penicilloides, Lemonniera aquaticaandTetracladium marchalianu

ISSN:0020-9309    

DOI:10.1002/iroh.19890740405

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

摘要:

AbstractThe sedimentation data of Gandhisagar Reservoir is presented and discussed. About 4.3 % gross capacity of Gandhisagar Reservoir was lost due to accelerated sedimentation from 1962 to 1975. Grain size analysis shows that the sediment consisted of 40.80 percent clay, 51.99 percent silt, 6.30 percent sand, 1.12 percent gravel. Suitable measures to prevent sedimentation are suggested.

ISSN:0020-9309    

DOI:10.1002/iroh.19890740406

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19890740408

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19890740410

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19890740411

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19890740413

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19890740415

出版商:Akademie Verlag, Berlin    

年代:1989

数据来源: WILEY