Ecological Status Assessment of Mountain and Semi-mountain Streams in the Aegean Watershed: Applicability of Biotic Indices BMWP and ASPT Based on Macroinvertebrates

摘要

In the past decades, the majority of the European countries have developed evaluation systems for freshwater ecosystems, including quality assessment trough the living organisms as biological quality elements. Based on this practice, the aim of the present study is to provide indicative ecological status estimation of mountain and semi-mountain streams in a poorly studied area of the North Macedonian - Bulgarian cross-border territory. We focused on four indices for benthic macroinvertebrates: Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT), Irish Biotic Index (B1) and EPT (Ephemeroptera. Plecoptera, Trichoptera) taxa richness. In total. 38 sites in both countries were sampled during autumn 2017 and spring 2018, all belonging to the R3 and R5 river type. The water quality was assessed from excellent to poor (I - IV class). The majority of the studied rivers do not achieve a good ecological status, mainly due to hydromorphological stress and habitat degradation (damming/mining/hydropower stations) and/or organic/anthropogenic pollution. Statistical treatment of the dataset indicated the strongest and most significant positive correlation between BMWP and EPT-taxa and negative correlation between BMWP and BI. The correlation between the General Degradation Score and the applied ecological quality indices clearly outlined a negative trend. The results confirmed the sensitivity of the indices BMWP and EPT to seasonal changes of the macroinvertebrate communities in running water ecosystems.