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.

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.

Little is known of the impact of agricultural activity on oysters in Chesapeake Bay tributaries. As a preliminary assessment of pesticide residues in oyster tissues, this study monitored more than 60 pesticides in oysters and overlying water in two tributaries of the Chesapeake Bay. Paired water and oyster samples were collected throughout 1997 from the Patuxent and Choptank Rivers which discharge into opposite shores of the Chesapeake Bay in Maryland. In water, herbicides such as atrazine, simazine, cyanazine, and metolachlor were present throughout the year with individual water concentrations peaking as high as 430 ng/1 in the late spring and summer and subsiding in the fall. These herbicides were not detected in the oysters even when concentrations were highest in the water. Another herbicide, trifluralin, was detected throughout the year at concentrations of less than 0.6 ng/1 and 0.4 ng/g (wet weight) in water and oyster samples, respectively. Several insecticides, such as endosulfans I and II, endosulfan sulfate, chlorpyrifos, α- and γ-HCH, p,p'-DDE, o,p'-DDT, trans-nonachlor, and trans-chlordane were also measured in both oysters and water at low concentrations.

The relationship between acidity and benthic invertebrate communities was investigated in two small streams in coniferous forests in central Jutland, Denmark, during 1992 and 1993. Stream pH was acid (mean pH 4.8 and 5.4) and alkalinity fluctuated greatly with mean values around zero. During rain events, water from springfed reaches upstream were mixed downstream with brown humic acid water with high aluminium content, and pH declined from circumneutral near the springs down to pH below 4 over a very short distance (0.5–1.5 km). The benthic invertebrate communities in the most acidic downstream reaches of both streams were dominated by filipalpian stoneflies, mainly Leuctra nigra (Olv.). Community composition remained very similar throughout the sampling period despite variations in pH. In the upper (neutral) reaches invertebrates intolerant of low pH such as Gammarus pulex L. were found. The concentrations of chloride and sulphate in the streams were more than double the concentrations in a nearby moorland stream indicating a strong impact of acidifying atmospheric deposition on the two forest streams. Results of this study indicate that afforestation with conifers on sandy Danish soils with low buffering capacity (about 25% of the total Danish land area) may lead to an increased acidification of surface waters and thereby also to an impoverished aquatic fauna.