The river Gvozdac (Serbia, Yugoslavia) is a small hill water current. It is situated on the mountain Goc and it belongs to the river basin of the river Ibar. During 1965, water micro-reservoir "Gvozdac" on the river Gvozdac was built for the hydroenergetic purposes, with the capacity of about 30,000 cubic meter and the maximum depth, in the present situation of about 2.5 m. Algological and saprobiological enquires have been performed on the water micro-reservoir, on the very river Gvozdac, on the river Ribnica and on some smaller stagnant waters on the given area, in the period between 1988-1994. The analysis have been shown that under the influence of antropogenic factors changes became apparent in the confluence and structure of algae flora as well as a degradation of water quality. The example of water micro-reservoir on the river Gvozdac indicates the destructive processes which are being developed in water micro-reservoirs and which should be stopped, as the significance of the small stagnant waters are not only in keeping and improvement of qualities of greater aquatorials and water tributaries of the river basins but also in the storing of biodiversity of aquatic assotiations in river basins (as well as in algae flora as one of the components).

The investigations of dynamics and composition of plankton, bottom fauna and fish community have been done at three localities (1-inflow, 2-the middle, 3-dam) at the Barje water reservoir (Serbia, Yugoslavia) during 1997. During winter period diatomea Asterionella formosa was dominant at all the localities. At the same time among zooplankton species Rotatoria group was dominant, with the emphasis of Polyalthra dolicoptera at the locality 2, while Keratella cochlearis was dominant at the localities 1 and 3. The present species are oligo- and betamezosaprobionts. Among the investigated bottom fauna species Oligochaeta and Chironomidae were present. The number of oligochaeta was between 1665-7878 ind./square m. By qualitative analyses the domination of Tubificidae family was present. It is known that the presence of this group of organisms and it's high number indicate the organic pollution of ecosystem. 30 individuals of the bighead, (Hypophthalmichthys nobilis) with the average weight of 5.6 kg was captured by net.

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.

Results on sea - water quality control and level of pollution in the coastal Southern Adriatic (Montenegro, Yugoslavia) were discussed from data collected in 1997. Investigations from Boka Kotorska Bay, coastal sea up to Bojana river mouth and in front of Bojana river mouth were presented separately. For above mentioned areas, basic hydrographic parameters, as well as the level of bacterial contamination were examined throughout the year (1996/1997 period). In Kotor Bay, which is the shallowest and exposed to the strongest land - based sources, as in the Tivat Bay, some changes influenced by anthropogenic eutrophication were already found.

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.

The paper summarizes the results on the quality of surface water of the Gornji Banat region (Serbia, Yugoslavia). Based on different classifications, statistic data processing was made and the conclusions on the usability of the water for irrigation are given. According to the results obtained there is an urgent need for efficient measures to improve the quality of canal water and the control the polluters.

As it consequence of soil erosion the contamination of water occurs. Namely, in the soil erosion process on the slopes of watersheds, together with soil particles (sediment) the organic matter, mineral fertilizers and nutrients are washed as well as pesticides applied in the agriculture production. By sediment reaching the water courses and reservoires the mechanical and chemical contamination of water is caused. In the paper sediment transport and losses of humus (organic matter) and nutrients (in the process of sediment transport) are presented in the three small torrential watershed in Western Serbia (Yugoslavia). Average annual specific transport of sediment was in the range between 50.0 cubic meter/year per square km (Lonjinski Potok) and 220 cubic meter/year per square km (Dubosnickog Potoka). In each tone of suspended sediment on average was 73.15-103.20 kg of humus, 2.88-5.93 kg of nitrogen, 0.63-1.50 kg of phosphorus, 2.63-3.81 kg of potassium, 6.76-14.27 kg of calcium and 5.18-9.33 kg of magnesium.

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 this paper given are basic characteristics and projected functions of the DTD (Danube-Tisza-Danube) Hydrosystem (Yugoslavia), then types, origin and some characteristics of muds - sediments in the hydrosystem channels. It is estimated that in hydrosystem channels gets in averagely about 1.28x10**6 tons of deposits annually, and of that amount in channels are settled about 0.64 x 10**6 cubic meter annually. In 1980-1996 period, it is mudded from channels of the main channel network averagely about 0.19 x 10**6 cubic meter/year, and in 1991-1996 period, usually only about 0.056 x 10**6 cubic meter/year, i.e. about 10 of average amounts which are deposited during the year. Also explained are numerous undesirable influences of muds - sediments on water quality in channels, as well as functions of the DTD (Danube-Tisza-Danube) Hydrosystem in general. At the end, measures for gradually improving conditions that are influenced by muds - sediments are, proposed.

Testing performed by five glass cups has been a try to show form and extent of water reservoir soil base influence on its water quality. At the some time a possibility of alleviation of eutrophication by means of certain safety precautions have been examined. During the test performed on a model of parameters (water temperature, air temperature, O2, chlorophyll a, total nitrogen, etc) have been monitored. The results of actions reffer to a fact a soil base influences deterioration of water quality, especially immediately after water reservoir filling, but the mentioned negative influence of the soil base could be decreased applying certain safety precautions.