Nitrogen and phosphorus contents in water, sediment and shoots of Phragmites communis Trin, and Typha latifolia L., as possible indicators of trophic state were used in the area of the Bardaca fish-pond. The results of total nitrogen and phosphorus contents during growing season indicate the hypertrophic state of waters in all locations.

The paper presents the results of investigation of benthic algae of the river Rasina. During April, 2001, it was determined 110 algal taxa from the divisions Cyanophyta, Bacillariophyta and Chlorophyta, which indicate the high biodiversity of algae in this river. With 97 algal taxa, Bacillariophyta is dominant. The community of benthic algae is typical for this kind of aquatic ecosystem during the spring period. Great number of algal bioindicators of highly polluted water indicates the presence of high concentration of organic compounds in this aquatic ecosystem.

In this paper we have presented the results of the investigations of phytoplankton carried out in the river Old Begey, from April 2003 till February 2004. The presence of 116 algal taxa of which 10 Cyanobacteria, 20 Euglenophyta, 50 Bacillariophyceae, 3 Chrysophyceae, 30 Chlorophyta and 3 Dinophyta was recorded. In the river Old Begey some rarer brackish species Entomoneis alata and Bacillaria paradoxa have also been found. The index of saprobity given on the basis of Pantle-Buck method indicated that the quality of water of the river Old begey belonged to beta-alfa-mesosaprobic category.

One of major direction of algology development in Serbia is completing data about bioindicating values for saprobic system based on the existing list of bioindicators. This work shows the results of several year's investigation of macroalgae in streams that belong to the Danube river watershed. Altogether, 72 taxa belonging to six divisions were found in the investigated streams. They were as follows: Cyanophyta (34 taxa), Rhodophyta (8), Xanthophyta (6), Chrysophyta (1), Chlorophyta (22) and Charophyta (1). Analysis of the list of species found in streams of highland regions of Serbia and the List of Indicatory Species reveals that 50% (36) of the species found have definite indicatory values. This work presents the data obtained for species that are not on the existing lists of indicators.