The influence of environmental factors on the structure of caddisfly (Trichoptera) assemblage in the Nišava River (Central Balkan Peninsula)

Monthly samples of caddisfly (Trichoptera) larvae were taken from ten localities along a 151 km long section of the Nišava River (eastern Serbia) during a one year study, with the aim to assessing the spatial composition of the caddisfly assemblage along the river gradient, to identify key environmental factors influencing its variability, to find out if caddisflies are suitable as biological indicators of water quality in this region, and to asses if the caddisfly assemblage in the river follows the river continuum concept. Twenty-three morphologically distinct taxa belonging to 14 genera were identified. The dominant family was Hydropsychidae with 70.34% of specimens examined, followed by Brachycentridae with 9.74% specimens. The longitudinal variability of the caddisfly assemblage has shown a clear dependence on physical and chemical parameters. The CCA analysis suggests that BOD5and concentration of total phosphorus are the most important factors in structuring the caddisfly assemblage. The species diversity was greatest at localities with the highest oxygen concentration and low nutrient levels. The caddisfly assemblage proved to be useful in identifying differences in environmental conditions in the Central Balkan region