摘要:

AbstractThe persistence under controlled chemical and physical conditions and the ability to respond to defined environmental changes was follow d in extremely simple (homogenous or 2‐phase) ecosystems with continuous or semicontinuous flow. In the homogenous case the Aufwuchs was removed. Primary productivity and community respiration were computed by means of continuous recording of dissolved oxygen. Under constant environmental conditions the systems usually exhibited slow oscillations of the ecosystem parameters around an equilibrium state. The temporal variations of functional criteria such as elimination rate of easily degradable organic substances or daily oxygen amplitude were slight in comparison to the significant random oscillations in individual numbers of the predominating species of phytoplankton and zooplankton. One of the mechanisms responsible for this functional stability may be the inverse relationship between biomass and activity per unit biomass as observed also in the laboratory models. If the sewage pond microecosystems after a shut down in the inflow were operated without any exchange of nutrients and gases they nevertheless maintained a very high level both of autotrophic and heterotrophic metabolism. Step forcing of nutrient (sewage) concentration, dilution rate or day length produced a new equilibrium state within 1 or 2 days, if the functional criteria mentioned above were taken as output signals. Also in the case of pulse forcing such a rapid adaptation was to be observed. This may contribute to the fact, that the turnover rate of the population was in the same range as the renewal rate of the water. The results are discussed with respect to short and long term effects of abatement of pollution from flowing and standing water

ISSN:0020-9309    

DOI:10.1002/iroh.19750600101

出版商:Akademie Verlag, Berlin    

年代:1975

数据来源: WILEY

摘要:

AbstractThe investigation of the epiphyton associated withScirpus validusVAHL. in Lake Wabamun commenced in May 1971 and continued until the end of August 1972. Seven stations encompassing heated, partially and non‐heated areas of the lake were investigated. From July 1971 until the termination of the investigation water temperature, dissolved oxygen and water chemistry were monitored. There were no large variations in these parameters except for water temperature and dissolved oxygen levels among the stations. However, there were increases in the dissolved silica, nitratenitrogen and phosphate‐phosphorus levels during the autumn and winter months at the heated stations while at a partially heated station only dissolved silica and nitrate‐nitrogen increased. The epiphyton at all stations showed a spring maximum, a summer minimum, and a maximum in the late summer/early autumn. The spring dominants at all stations wereFragilaria capucinaandDiatoma elongatum. During the late summer/early autumn maximum diatoms were dominant at the non‐heated stations while chlorophycean species were dominant at the heated stations. The heated water caused a decrease in the number of species and a corresponding increase in the importance of a few species at the heated stations. The major impact of the heated water, however, was an extension of the period of open water and the corresponding increase in mean yearly standing crop size in the heate

ISSN:0020-9309    

DOI:10.1002/iroh.19750600102

出版商:Akademie Verlag, Berlin    

年代:1975

数据来源: WILEY

摘要:

AbstractThe examinations showed that the phosphate supply for the planktonic primary production comes almost exclusively from the influxes. The nutrient pool in the hypolimnion and in the sediment does not play a leading part. Evidently, that is often so in reservoirs.Both the phytoplankton (the most frequent species areAsterionella formosaandFragilaria crotonensis) and the concentration of phosphate fractions are subject to considerable seasonal variations. TheAsterionellaspring maximum, typical of this reservoir, is released directly or indirectly by meteorological factors. An adequate orthophosphate concentration is a basic condition which is accomplished, however, nearly every year. The autumnalFragilariamaximum begins when a definite mixing depth hae been achieved. The breakdown of a diatom maximum is caused almost at all times by exhaustion of the phosphate reserves.

ISSN:0020-9309    

DOI:10.1002/iroh.19750600103

出版商:Akademie Verlag, Berlin    

年代:1975

数据来源: WILEY

摘要:

AbstractSeasonal variation of the biomass of plankton in Lake Yunoko, a eutrophic lake in Japan at an altitude of 1478 in, was followed by measuring simultaneously the quantities of chlorophyll, protein, RNA and DNA in water samples harvested from different depths at a definite site in different seasons of a year. The contents of the four cellular constituents and the sum of them in a given water column showed characteristic seasonal changes during the year. Various ratios derived from the four contents were grouped into two distinct types; one is the winter‐spring type and the other the summer‐autumn type. It was found that the sum of the four contents and the ratio of the protein‐content to the RNA‐content were quantitatively related to the chlorophyll‐content of the water. Based on the assumption that a certain water sample contained only photosynthetic plankton, analyses were made to estimate the proportions of photosynthetic and non‐photosynthetic plankton to the total planktonic mass, the growth rates of these plankton, and the net productivity

ISSN:0020-9309    

DOI:10.1002/iroh.19750600104

出版商:Akademie Verlag, Berlin    

年代:1975

数据来源: WILEY

摘要:

AbstractThe horizontal distribution of Ceratium hirundinella (MÜLL.) BERGH was investigated in Lake Erken at ten stations in the summer of 1969. Abundance, total length and number of horns were studied. The conclusion is that the lake contained a horizontally uniform population of the alga. A correlation between form variation and the growth curve of the population was found, which can be explainable with PEARSALL'S (1929) theory, linking form variation with cellular metabolism

ISSN:0020-9309    

DOI:10.1002/iroh.19750600105

出版商:Akademie Verlag, Berlin    

年代:1975

数据来源: WILEY