Trophic Structure of Macrozoobenthos in Permanent Streams in the Eastern Balkans

The present study provides data on the trophic structure of the benthic macroinvertebrate communities in mountainous and semi-mountainous small streams and river sections belonging to Mesta, Struma and Vardar River catchments from 7th Ecoregion. The benthic macroinvertebrates were assigned to seven Functional Feeding Groups. We analyzed their trophic structure and the dynamics in different seasons. The level of similarity between the sampling localities was analyzed in the context of both the river typology and the water catchment. A comparison between the two trophic indices was conducted in order to analyze the advantages of the application of these indices for assessment of the ecological status at the studied sites. We found that the trophic structure of the benthic macroinvertebrate communities in ostensibly typologically similar river sections differs at the undisturbed vs the impacted sampled sites. To a large extent, these differences were also determined by the presence of anthropogenic influence that resulted in the predominance of deposit feeders amplifying on higher disturbance on some of the studied rivers. Long-term negative pressure has led to changes in microhabitats that affect the structure and functioning of the aquatic ecosystem by transformation of the trophic structure of the macrozoobenthos.