Lake ecosystems determined by trophic conditions, accurately defined Ecological status of protected area. Trophic condition of water of Lake Skadar and two rivers, the inflow Moraca and the outflow Bojana was described via plankton data considering abundance of phytoplankton, seasonal dynamics of organotrophs, cyanobacteria, total coliforms, plankton biodegrading potential and nitrogen fixing bacterioplankton. The trophic potential for phytoplankton growth has been detected in late autumn throughout September-November 2004, contrary to early summer June-July 2005, and adverse growth of bacterioplankton in May, June and September 2005, respectively. The results of quantitative analysis of coliforms showed good relation of Lake Skadar and Ada Bojana, contrary to similarities between Moraca River and Ada Bojana estimates in accordance with the Pantle-Buck index. Nevertheless, investigation pointed out Lake Skadar beta-mesosaprobic level and moderate self-purification rate. In evaluating trophic conditions the good ecological potential of protected area has been proposed.

This paper shows the results of research of some phytoplankton and saprobiological characteristics of water in reservoir Grliste and the flowing rivers during the period of January 2001 to December 2007. During this period of researching, phytoplankton community was characterized by forms of Bacillariophyta, Chlorophyta, Cyanophyta, Chrysophyta, Pyrrophyta and Euglenophyta. Saprobiological analyses using bioindicatory species of algae showed oligosaprobic and beta-mezosaprobic characteristics of water in the reservoir. The analyses showed the poor water quality of Lesovacka and Lenovacka rivers which flow in reservoir. This water was determined as beta-mezosaprobic and alfa-mezosaprobic type. The phytoplankton was characterized by forms of Bacillariophyta, Chlorophyta, Pyrrophyta and Euglenophyta.

During the field research of phytocenous characteristics of the Moravica river flow and the influence of anthropogenic pollution, hygrophilous ass, Salicetum albae-fragilis (willow grove-shrubs in moist habitats) which grows in the middle reaches of the Moavica, has been found. The community develops in the middle reaches and it indicates highly polluted waters. The aim of this paper is to establish phytocenous contents of the community and ecological conditions of the habitat (indicatives of water quality of the Moravica river) based on ecological index of vascular plants.

During 2005-2006 the seasonal researches were taken place aiming to investigate the influence of the urban waste water on the qualitative and quantitative structure of the community of macrozoobenthos in Gabrovacka river. For this purpose five sites were determined and the sampling of the macrozoobenthos was organized on the seasonal level using Surber net.

In the project Quality of Drinking Water of Banja Luka City, during 2007 the colony of zoobentos around the water factory is followed. The composition of colony is different in both season and horizontal profile. The quality of water in litoral area of river is much worse, because polluted water from ambiental settlement and that is indicated by major number of Tubificidae. During monitoring of the states there was a change of qualitative and quantitative composition of colony, also and the change of individual domination of taxons.

The paper presents the results of aquatic macroinvertebrates community analyses of the Moravica river with the aim to evaluate saprobiological status. Sampling were carried out tree localities during 2003 and 2004.