During the period February 1999 - February 2000 samples of water taken monthly from the area before the outflow of river Crn Drim from the Lake Ohrid, in purpose of qualitative and quantitative investigation of phytoplankton community. During the period of investigation, the phytoplankton community was characterized by forms of Cyanophyta, Bacillariophyta, Chlorophyta, Chrysophyta, Pyrrophyta and Euglenophyta. Qualitative analysis indicated that algae of the division Chlorophyta and Bacillariophyta are dominant in the phytoplankton, while the results of the qualitative analysis showed that forms of Bacillariophyta are dominant. Seasonal dynamics of phytoplankton is characterized by autumnal and winter domination of Bacillariophyta, spring maximum of Chrysophyta and summer domination of Pyrrophyta. The total number of algae varied between 1500-95,700 ind/l in August and February 2000, respectively.

In this paper are presented the investigation of macrophytic vegetation along Macedonian shore of Lake Ohrid (Radozda-Sv.Naum). The meterial were collected from 59 localities. The results of investigations show that in investigated localities were evidenced 25 different plant species. The number of macrophytic species in different localities vary from 2 to 18 macrophytic species. The differences in the number of macrophyte species are most due to the different ecological conditions in the investigated localities: temperature, light regime, type of soil, configuration of the lake bottom, water level, nutrient amount etc.

In order to determine the dynamic of biomass of stoneworts from Lake Ohrid as a function of the trophic state of the water, we collected samples from four different localities. The localities Sveti Stefan and Mazija, were characterized by oligotrophic state of the water, while the other two Grasnica and Daljan were characterized by eutrophic-mezotrophic water quality. The stoneworts samples were taken from 4-5 different depths from each investigated locality. The results of our investigations have shown that higher trophic level of the water from the littoral region of the localities Grasnica and Daljan (especially in the points of inflow of river Grasnica and Daljan) decreases the amount in stoneworts biomass compared with the biomass of stoneworts collected from the first two localities that characterizes oligotrophic character of the water.

Faculty of Science, University of Kragujevac (Serbia, Serbia and Montenegro), has developed SeLar Information System (Serbian Lake and Reservoirs Information System) which provides all the information of Serbian lakes and water reservoirs. Information system is needed for transfer of knowledge and informations, cooperation among participant in management and support of sustainable using of water resources. The paper presents the basic system components and some applications examples.