Important differences in the structure of fauna communities of their deepest parts of benthos were found in the investigation of several water reservoirs (Gruza, Grosnica, Barije, Bor, Vlasina and Medjuvrsje) on the territory of Serbia (Yugoslavia) lasting several years. The pronounced alterations of the structure are in the correlation to the pronounced degree of eutrofication was also established according to other indicators, above all according to the concentration of biogenic salts and the amount of organic substances. Characteristic group and taxa of the fauna of benthos which point to certain level of eutrophications were separated.

Monthly sampling in the Grosnica water reservoir near Kragujevac, Serbia (Yugoslavia), was carried out in the period October 1996 - September 1998. Comparison of the results with those obtained in 1950-1952 revealed changes in the qualitative and the quantitative composition of zooplankton. The presence of a considerably greater number of species was recorded, including some that were registered for the first time in this reservoir and which represent a very significant component in the dynamics of its zooplankton. A multi-fold increase of zooplankton production was also observed. The number of recorded species fluctuated from 26 in the winter to 59 in the summer. Average total abundance of zooplankton ranged from 100.7 ind./l (late spring to 2508.6 ind./l (summer). The results indicate an intensive process of eutrophication in the Grosnica water reservoir, the oldest artificial lake in the this part of Yugoslavia.

The investigations of qualitative and quantitative composition of plankton and the bottom fauna of the Tisza river, Serbia (Yugoslavia), were conducted during 1998. According to the analyses of the indicator species of hydrobionts, saprobic index was calculated, and the estimation of the water quality of the lower flow of the dam near Novi Becej on the structure and abundance of the investigated organisms.

During three years period from 1991 to 1994, investigation of the river Kolubara (Serbia, Yugoslavia) was carried out along 35 km of water course from Valjevo to Lajkovac. The macrozoobenthos community was composed of 117 determined taxa. Of the found taxa Oligochaeta were the most diverse with 40 taxa determined. The greatest diversity of macrozoobenthos community was foound at the river section in Valjevo, upstream the mouth of Gradac (69), while the community was most uniform downstream Valjevo at Bela Stena (24 taxa). A decrease as well as an increase in the macrozoobenthos diversity was not in accordance with similar decrease or increase in saprobic index values since they were in narrow range from 2.37 to 2.59.