The most important results of the program "Structure and functioning of ecosystems" are: - High-mountain lakes on the limestone geology - opposite to the lakes on non-carbonate geology those lakes are not sensitive to acidification but they are prone to eutrophication. Results obtained from EU-program showed that the lakes from the Julian Alps differ significantly from other high-mountain lakes in Europe. There are differences in the water chemistry, reactions on external influences and in composition of flora and fauna. Important contribution of the program was to understand relation between earthquakes and bio-production in the lakes and mechanisms of deposition of pollutants in sediment. Part of the program, connected to introduction of alien species (fish) into the lakes, revealed a highly negative consequence of such activity. - Oscillations of water regime and its influence on aquatic plants - deteriorations of wetlands all over the world and especially in Europe makes such type of research very actual (also within the frame of Ramsar's convention of wetlands conservation). In the last five years research activities were performed on the lake Cerkniško jezero. Apart floristic research most of activities were focused on research of vitality of the roots of a common reed (Phragmites communis) in saturated and unsaturated zone of the lake's bottom. Availability of nutrients in a root zone and processes of mineralization were in the focus of research. Measurements on vitality of the roots based on ETS activity are among the first of such research. - Impact of UV-b radiation o terrestrial and aquatic organisms - the activities were run in a program connected to EU project UV-AQTER. Results revealed that plants exposed high UV-b radiation synthetize UV-b absorbing compounds to reduce damages of body tissues. Later on we expand analyses on other terrestrial and aquatic plants, particularly on algae. Those experiments were not performed before and results of our experiments in impact of UV-b radiation on algae are among the few known so far. - Research on eco-physiology in some selected animal groups - they involved potential and realized oxygen supply of the organisms in normal and under stress conditions. Relation between potential and realized oxygen consumption is a measure of fitness of the organisms to the environmental conditions. Experiments were performed on aquatic organisms (water flies, shrimps and bacteria) and also on fertilized fish eggs as well as newly hatched fish. Combination of measurements of potential and realized oxygen consumption is one of the most promising methods in ecology. - Long-eared owl (Asio otus) - research we performed contributes important information on relations between long-eared owl and its prey in SE Europe. Especially high value represents a long-term data series which revealed that changes in population size of small rodents could be cyclic also in SE Europe. The same data help us to understand same basic relations between predator and prey, especially role of so called compensatory prey. We recorded and described so far unknown despotic behaviour in selection of nest sites which it is controlled by prey availability. - Taxonomy of lower crabs - research activities were oriented mainly in subterranean environment especially in karstic caves, where we found several new species. Most of them are inhabitants of specific environment, known as epikarst zone. The zone is not well known at all but it appears it is important ecosystem, rich in specific fauna.