ISSN:0020-9309    

DOI:10.1002/iroh.19920770102

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractUsing the new Energy‐Transport‐Reaction Model, the nitrogen‐cycle is presented in relation to energy flow in a system. This model is applied exemplary to three degraded inland water bodies. The decrease in the density of energy flow in a spatially limited system provides the framework for this model. By this model the N‐cycle can be observed in relation to other abiotic and metabolic processes. The N‐cycle proves to be an important indicator, sensitive to disturbances in the hydrologic cycle. A poorly managed hydrologic cycle will increase resource losses from the watershed, and stimulate the formation of loss processes. The model allows an evaluation of a catchment's management according to its ion losses related to its nitrogen losses. Based on a longterm sustainable function of a catchment the integrity of the system is measured by its degree of closure of material cycles and lack of losses. Moreover, loss‐minimizing management practices can be derived from the model. Planning and management can be directed towards this goal of minimizing losses and evaluated

ISSN:0020-9309    

DOI:10.1002/iroh.19920770103

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractA detailed mass balance on nitrogen was carried out in shallow and hypertrophic Lake Søbygård during 4.5 years before through 2.5 years after a 36 % reduction in nitrogen loading. Annual mean loss rate of nitrogen was 159–229 mg N m−2d−1before the loading reduction and 125 mg N m−2d−1after. In spite of a short hydraulic retention time (18–27 days) the proportion of nitrogen loading lost in the lake was high (38–53 %) and not affected by changes in loading. Calculated denitrification accounted for 86–93% of the loss rate, while 7–14% was permanently buried. Marked seasonal variations in the loss percentage were found during the season, ranging from 23 % in first quarter to 65 % in third quarter. The seasonal variation in the loss percentage of nitrogen showed a hysteresis like relationship to temperature, with a high percentage in fourth quarter. This suggests that the amount of available substrate, which mainly consists of sedimentated phytoplankton, accumulated during summer, is an important regulating factor. The ability of various published input‐output models to predict the observed changes in in‐lake nitrogen concentration in Lake Søbygård was tested. This study has further confirmed that small lakes with short retention and high nitrogen loading may significantly reduce the nitrogen loading of downst

ISSN:0020-9309    

DOI:10.1002/iroh.19920770104

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe nitrogen budget of Lake Gr. Müggelsee (mean depth 4.85 m, area 7.12 km2) was calculated from weekly measurements of nitrogen transformations from 1978 to 1984. Common mass balances for nitrogen were completed by determination of dinitrogen fixation in order to calculate denitrification as residual budget component and resolved for distinct seasonal periods. N sedimentation was calculated from internal P balance. Influence of flushing rate on loss processes were analysed by comparison of years with very different runoff. Time series analyses and multiple comparison show a relation of hydraulic flow, nitrate load, in‐lake nitrate and N elimination to the seasonal cycle of irradiance. Denitrification is the most important loss process and exceeds the effect of sedimentation. Other in‐ and outputs (precipitation, swimmers, volatilization) are rather stochastic and of lower quantitative importance. Nitrate leaching from the catchment and turbulent mixing within the lake are discussed as determining factors of in‐lake nitrogen

ISSN:0020-9309    

DOI:10.1002/iroh.19920770105

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractResults from thirteen years of weekly observations are presented on the nitrogen cycle in Lough Neagh. The data comprised catchment and atmospheric inputs, output via the outflow and calculated losses by sedimentation and denitrification. Nitrate‐nitrogen in the rivers is the dominant input fraction and the nitrate loading has increased over the period observed. 52 % of the input N sediments to the lake bottom, but 65 % of this is lost by denitrification. In spite of increasing nitrogen inputs, the summer soluble nitrate concentrations have decreased due to uptake by a perpetual crop of the cyanobacteriumOscillatoria agardhiiGOMON

ISSN:0020-9309    

DOI:10.1002/iroh.19920770106

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe extent of decline of reed belts (Phragmites australis) during last decades has been established by using aerial photographs of the mesotrophic lake Parsteiner See and the eutrophic lake Müggelsee. Final standing crop and nitrogen accumulation within the above‐ground plant biomass of 15 different sites of 8 lakes correlate with nitrogen availability indicated by both dissolved nutrient content of the sediment and nitrogen content of biomass during the main growth period. Reed stands well supplied with nitrogen show high shoot loss and compensatory tiller growth till late in the season. Some results demonstrate a delayed switching from the vegetative phase to the generative one and lowered allocation of reserve material to the rhizome as at least one of the factors responsible for lowering stability of the reed be

ISSN:0020-9309    

DOI:10.1002/iroh.19920770107

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractAn analytical registration of P‐transport processes in intact sediment cores from the shallow reservoir Radeburg II (near Dresden, Saxonia, Germany) was possible by application of KH232PO4and followed by sequential P‐fractionation (PSENNERet al.1984). Under oxygen free conditions and sufficient nitrate supply an activity accumulation was found in the uppermost sediment horizon. Nitrate influences above all the BD‐fraction (reductant soluble P), so that an interaction between nitrate and the iron binding system could be proved. It could be shown by means of activated sludge (a model object for microbial polyphosphate accumulation from a lab plant qualified for biological P‐ and N‐elimination) that added KH232PO4was bound within 5 h to about 75 % in the NaOH‐fraction. The saturation of iron compounds in the activated sludge took place immediately after KH232PO4had been added. In the same time the portion of the microbial immobilization of added32P amounted to 7 % in the high‐iron sediment from the Radeburg reservoir, whereas evidently in the heat‐ and HgCl2‐sterilized sediments this portion was additionally ascertained in the

ISSN:0020-9309    

DOI:10.1002/iroh.19920770108

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractAn attempt has been made to examine the extent to which seasonal periodicity of lacustrine phytoplankton corresponds to the general concepts of the theory of ecological succession. The study was carried out on an eutrophic lake (Aydat, France). As REYNOLDS(1980, 1984) suggests, the seasonal periodicity of phytoplankton is an autogenic succession which may be perturbed by allogenic physical processes that change the initial direction of the succession. Thus, in this lake, only spring succession of phytoplankton can be considered as a true succession, consistent with the theory of ecological succession in that it was a directional and predictable phenomenon leading to an increasing complexity of community.

ISSN:0020-9309    

DOI:10.1002/iroh.19920770109

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractMathematical modelling of the ecosystem of the North‐West shelf of the Black Sea is based on the method of aggregation and averaging with the subsequent hierarchic decomposition (BELYAEV, 1987; BELYAEVand KONDUFOROVA, 1989). This approach includes the step‐by‐step comparison of the modelling results with field observations. The observations have been performed during the integrated oceanographic expedition of the research vessel “Professor Kolesnikov” (1987), for the first time specially organized to verify the modelling results. The comparison of the results of modelling and observation demonstrated that their agreement is satisfactory quantitatively and qualitatively. The efficiency of using models of optical fields for verification is a

ISSN:0020-9309    

DOI:10.1002/iroh.19920770110

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractOver a two‐year period, each of the threeDaphniaspecies in two lakes with different pressure by fish and invertebrate predators exhibited different defensive reactions: predator avoidance in space (Daphnia hyalina), seasonal morphological changes (Daphnia cucullata), and a combination of both (Daphnia cristata). Body size and general susceptibility to predation, combined with predators' preferences were most likely responsible for the kind of defence in each of the threeDaphni

ISSN:0020-9309    

DOI:10.1002/iroh.19920770111

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY