The Mostonga, once the tributary of the Danube river, now a water-stream with a conducted regime it represents an important water-streams in West Backa (Serbia, Yugoslavia). The most wide-spread hydrophytes (i.e. plant species with the biggest abundance, covering values and occurrence degree) are: Wolffia arrhiza, Lemna gibba, Lemna minor, Lemna trisulca, Spirodela polyrrhiza, Ceratophyllum demersum, Elodea canadensis, Vallisneria spiralis, Stratiotes aloides, Nuphar lutea, Bolboschoenus maritimus, Typha angustifolia, Typha latifolia and Phragmites communis. Based on the analysis of bioindicating values of mentioned hydrophytes of the Mostonga it can be concluded that the present plant species are significant indicators of eutrophication (considerable organic pollution) as well as the increased contents of nitrogen and nitrogen compounds (nutrients), presence of salt in the soil and weakly aerated and mud base.

During the 1996-1997 period, dynamics and structure of zooplankton and benthos in sugar mill canal in Crvenka (Serbia, Yugoslavia) were studied. Two representative sampling sites were chosen, while the third one served as a control site, providing it has no impact on cage culture. The canal section where the cages were established, had previously been drainage and dredged. Immediately after the refilling, the zooplankton qualitative structure was scarce, with dominating Rotatoria. Two months later, the situation improved and Cladocera and Copepoda emerged. Those two groups of organisms have the major role in enhancing the commercial feed consumption Soon after the refilling, the benthos was reestablished. Sample analysis shows the presence of Oligochaeta and Chironomidae. Qualitative and quantitative analysis of benthos points out no significant difference between the canal sections upstream and downstream the cage culture.

In this paper the short review of the results of calculation of the coincidence between the water level and quality parameters at the gauging station Cuprija-rail bridge (Serbia, Yugoslavia) is presented. The basic principles of the applied method and criteria for the estimation of the statistic significance of coincidence indicators are given. At the end of the analyses and comments of the obtained results, as well as the possibility for application of this methodology are given. The paper gives numerical quantities of the estimated indicators of statistical significance of the coincidence of water level and quality parameters of groundwater. Also, the graphical illustration, which shows the common exceeding probabilities of the water level and quality parameters, is presented.

Amplified and accelerated eutrophication process is a characteritic of a whole variety of small and medium-sized water-bodies, such as channel systems, microreservoirs, ponds, lakes and bank regions of many even bigger ecosystems. During the process, in relatively short period of time, the upper capacity limit of a certain biotop is far too exceeded, which leads to reduced ability of ecosystem's autopurification. As a consequence of such degradation, ecosystem faces a serious discrepancy between members of a biocenosis e.g. in ration producers/consumers/decomposers, which, in the end, causes destruction, e.g. dystrophy of the hydroecosystem. The introduction of diverse fish communities, can, therefore, be one of the basic measures for enabling a sustainable trophic stability, in a sense of keeping a dynamic balance. This measure includes carefully planed fish community - it should consist of three basic components of a trophic food web (planktivore and macrophytovore, bentivore and carnivore). Apart from enabling certain biodiversity considering particular fish species (both quantitative and qualitative), care must be inevitably taken of age structure, as well as fish stock and fishing dynamic, concerning the number, quantity and age.

Mussels (Mytilus galloprovincialis) were collected from the locality in the vinicity of the Institute for Marine Research in Kotor (Montenegro, Yugoslavia). The concentration of Cu (copper), Cr (chromium), Fe (iron), Zn (zinc), Ni (nickel), Mn (manganese), Pb (lead), Cd (cadmium), Al (aluminium), Ca (calcium) and Mg (magnesium) were determined in whole mulles, gills, pedal muscle and in rest of soft tissues. The data obtained in this research were compared with the results reported by other investigators.

In this paper the results of determination of natural waters from the territory of the township Smederevska Palanka and Rekovac (Serbia, Yugoslavia) are presented. The content of metals in waters was determined by the AAS method and other parameters were determined by spectrophotometric and potentiometric method.

In previous works numerous specific changes of water composition in the Danube backwater effects Iron Gate 1 reservoir (Yugoslavia), have been initiated. By studies of conditions of generation and composition of sediments, the models denying importance of assumption on sedimentological features of deposited materials foreseen by the project, have been established, as it was confirmed with more details by newer investigations. The new data on the character of sediments coincide in all elements with changes of water composition, which was formerly presented, thus the knowledges of these phenomena being in that way more important. The data on composition of the deposited material, the macro and micro-composition are of great importance to perceive the influence of new sediments to the quality of surface and groundwater, especially of the sources for water supply, then in a long term for the sudden high risk processes corresponding to a chemical time bomb. Data have confirmed validity of the model of intensified deposition of allochthonous material with plankton and influence of this phenomenon to the processes trough the downstream section.

Previous studies clearly indicated that membrane enzymes - ATPases i.e. Na, K-ATPase and Mg-ATPase, responded to presence of various organic and inorganic pollutants. In this work effect of mercury and cadmium on these enzymes activities was investigated in synaptic plasma membranes partially immobilized on microliter plate. Comparing those activities with the control enzyme activities obtained with native and partially immobilized mambranes it was concluded that: a. both metals exerted a concentration-dependent inhibition of investigated enzymes, b. for partially immobilized membranes estimated half maximum inhibition (IC50) values for Na, K-ATPase were IC50 (Hg) = 0.9 micromol/cubic cm, IC50 (cd) = 35 micromol/cubic cm and for Mg - ATPase IC50 (Hg) = 3.5 micromol/cubic cm, IC50 (Cd) = 36 micromol/cubic cm; for native membranes IC50 for Na,K-ATPase were IC50 (Hg) =3.3 micromol/cubic cm, IC50 (Cd) = 2 micromol/cubic cm and for Mg ATPase IC50 (Hg) = 2.3 micromol/cubic cm, IC50 (Cd) = 0.2 mmol/cubic cm. Obtained results indicate avaibility of microtitar plates for partially immobilization of membranes with aim to form a new biosensor for heavy metals detection.

In 1996 (March and June) the mineral water "Rudovci" was sampled in its spring in the village Rudovci, Serbia (Yugoslavia). The physical-chemical analyses have shown that the temperature of the water was 180 deg C with sodium-carbonate content. It has been considered that the quality of water was variable in a short period from 3 months. Comparing the analyses of the mineral water from 1996, we can consider some remarkably distinctions in some chemical elements. The chemical analyses made in 1996, have shown changes in following contents: magnesium (47.6 and 64.5 mg/l); sodium (1313 and 1355 mg/l); iron (2.35 and 3.76 mg/l); boron (5.2 and 4.8 mg/l); arsenic (0.08 and 0.06 mg/l). In 1974, the chlorine content was 28.4 mg/l, but about 218 mg/l in 1996. The nitrate content varied from high (19.2 mg/l) in 1974 to low (about 0.75 mg/l) in 1996.

Hydrological, psamological and pluviographical measurements in experimental watershed area in the watershed of River Topciderska (Serbia, Yugoslavia) was analyzed. Interrelations between suspended sediment concentration in streams on the one hand and runoff, rainfall, rainfall intensity and index of previous rainfall on the other hand was came from this analyze. Effects of these parameters on suspended sediment concentration was considered for a single rainfall epizode, during the period of torrential waves and as annual value. Specific coefficients (coefficient of annual rainfall structure and coefficient of annual runoff structure) were used in this paper, with help of them effects of torrential waves and intensity rainfall on average annual suspended sediment concentration were considered.