The protected natural goods of the swamp Zasavica is situated in the north part of Macva (Serbia, Yugoslavia). It is parallel to the flow of the Sava river, which leads to the fact that it used to be the riverbed of the Sava and also of the Drina river. It is interesting for its variety of the plant and animal species. The investigations have been done during autumn period 1997, when the investigated groups were the most heterogeneous. It included algae, Rotatoria,Cladocera, Copepoda and Hydracarina. Among algae, Bacillariophyta were dominant. Among all the investigated groups Rotatoria were the most heterogenous, with great number of the species that are rarely present. Also, some Cladocera species were rare. The estimation of the water quality is given according to the bioindicator species.

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).

During hydrobiological investigations of the river Dulenska (Serbia, Yugoslavia) in June 1996, algological samples were taken at this river. In the algae community are found 34 taxa from two divisio: Bacillariophyta (28) and Chlorophyta (6). While qualitative composition of the algae colony was relativelly uniformed quantitative one was changeable along the course of the Dulenska river. By saprobiological analysis, it was found that the quality of water was changing along the course of the river. At the upper and middle course of river the water belonging to the second class. At lower course of the river (below Rekovac) water quality was getfing worse and it belonging to the third class.

The investigations have been done in Krstonosica shaft at 3 points, in February, May and October 1995, and in January and April 1996. They included algae, Rotatoria, Copepoda, Cladocera, and Hydracarina. The species from divisio Bacillariophyta were presented most among the algal species, with 56 species, then from divisio Chlorophyta, with 26 taxons, Euglenophyta 11, Cyanobacteria 9, Pyrrophyta 3, Xanthophyta 2 and Chrysophyta 1. Among animal groups the highest number belonged to the Rotatoria group, 111 taxons have been determined. The highest number was found during autumn season (86), then in spring (73), and only 14 species in winter. The species that mostly prevailed were phytophyl species. The Cladocera group was present with 18 taxons. The phytophyl species from overgrown plants again prevailed. The Copepoda group was present with 10 species and the phytophyl species were prevailed. According to saprobiological characteristics the greatest number belongs to beta-mezosaprobionts, then oligosaprobionts. A small number of species indicates to the eutrophication process and organic pollution of water.

The main characteristics of catchment area of Boka Kotorska Bay (Adriatic sea, Montenegro, Yugoslavia), are high slope, carstic structure of ground, high precipitation (over 5000 mm a year) and high run-off of rain water. All rainwater is transported trough carstic ground structures quickly appearing in numerous sources along the sea cost or ones located on the bottom of the Bay. The large volume of freshwater which permanently empty into the Bay has the strong influence on the aquatic environment (salinity, temperature, transparency, etc.) and biota (abundance of the species) as it has been observed in the parts of Boka Kotorska Bay (i.e. Morinj and Risan Bays). The abundance and number of species are the good indicator of changes of aquatic environment and hydrological changes as well as of the capability of aquatic organisms to adapt quickly on the severe changes of conditions.

In April 1997 and 1998 investigations of algae, Rotatoria, Cladocera, Copepoda and Hydracarina were conducted. The investigated localities were 8 small water bodies at around 800 m a.s.l., at Mali Krs, in the surrounding of Bor, Serbia (Yugoslavia). The aim was to examine composition of these groups and to give the evaluation of the quality of water. Among algae, according to the number of taxons, the dominant group was Bacillariophyta (45), then Chlorophyta (17), Cyanophyta (3), Euglenophyta (4), Xanthophyta (1) and Pyrrophyta (1). Rotatoria were present with the highest number of taxons among microfauna. In these investigations 48 taxons were present. The highest number of taxons was among Cephalodella, Corurella, and Trichocerca. Among Cladocera 4 taxons were present, and among Copepoda 9 taxons, and all the present species were found in our previous investigations. Hydracarina were present with 3 species, also with high diversity. Around two thirds of all taxons are oligosaprobionts, which indicates to the good quality of the water.

In order to increased the amount of water in Sjenica water reservoir (because of higher production of electric energy by hydroelectrical power plant), stagnant waters of Pester field were irrigated to Vapa river and Sjenica lake. Former swamp areas and theirs life communities, represented specific biological filter in Pester high, a kind of natural lagoons, where big amounts of polluted water with nutrients were spent a processed (especially salts of P and N) were characteristic for exact area because of intensive cattle production. After the irrigation on Pester field, raw, polluted water with the large amount of nutrients by Vapa river get to the Sjenica water reservoir where they represented main cause of eutrophication and degradation of water quality in this aquatorium. Heterogenic and numerous algal association in canal of the Pester field is nearly leftover of previous specific algological flora which testifies the presence of species Chaetophora incrassata Hazen (new habitat in Serbia), the first class water indicator.

In the period October 2001 through November 2002 in six series parallely with physico-chemical and hydrobiological analyses, the content of photosynthetic pigments was determined in algae in the region of flow-through reservoirs of "Djerdap 1" and "Djerdap 2" on the profiles of Smederevo, Ram, Veliko Gradista, Donji Milanovac, Tekija, Kladovo and Radujevac. The samples were taken by a pump from the river midstream at the depth of 1-0 m (composite sample), while in the vegetation period April, June and September, the samples were taken at the depth of 5 m. The peak concentration of chlorophyll-a, the biological indicator of trophic condition, was recorded in the month of April in the Smederevo profile (30.2 mg/cubic meter) at the depth of 1-0 m. The lowest values of chlorophyll-a in all studied cycles were recorded in the Radujevac profile (below the dams) with the mean annual value of 1.8 mg/cubic meter. Chlorophyll-c occurs as the subdominant photosynthetic pigment. Values of chlorophyll-c were higher than chlorophyll-a in the month of June on the Donji Milanovac profile in the analysed sample taken at the depth of 5 m. Higher values of chlorophyll-b were recorded in the course of the vegetation period in the month of June on the profiles of Smederevo, Ram, Veliko Gradiste and Donji Milanovac at the depth of 1-0 m.

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.

The river Crnojevica is a subject of lasting manny years physicochemical and microbiological investigations, which show worring pollutants presence into the water current. This work represent preliminary investigations of Crnojevica river water algal flora (phytoplankton and phytoperiphyton), carrying out over summer period of 2004. Aim of the investigation was to point, based on algal analysis, as reliable indicators of water quality and ecological status of an aquatorius, the need to protect the river from permanent communal and industrial waste water pollution. The hyperproduction of phytoplankton in the investigation period was stated, but it varys along the current, in accordance with efluent inflow. On the base of saprobiological analysis of phytoplankton, determinated water quality was in class 2, till the worse was noted at T2 measure place, on the inflow place of Rijeka Crnojevica settlements sewage.