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.