Ecological Status Assessment of the Strumica River Watershed Based on Macroinvertebrates – A Step Towards the Implementation of the EU Water Framework Directive in the Republic of North Macedonia

Abstract

The aim of this study was to provide ecological status/potential assessment of the water bodies in the Strumica River Watershed based on macroinvertebrates, as a step towards the implementation of the WFD in the Republic of North Macedonia. The material collected during June 2015 from 13 river water bodies, as well as from 2 heavily modified water bodies - reservoirs Turija and Vodocha was examined. The following indices were used for ecological status assessment: EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa richness, Biological Monitoring Working Party Score (BMWP) and Average Score Per Taxon (ASPT). Canonical Analyses (CA) confirmed that macroinvertebrate communities significantly differentiate between water bodies, indicating different ecological conditions. The biological assessment based on applied indices BMWP, ASPT and EPT taxa richness indicated a "healthy" river sector on the Koleshinska, Lomnica and Bezgashtevska Rivers and could be selected as indicators for reference conditions. Dominance of Chironomidae and Oligochaeta, as well as metrics values indicated high levels of ecosystem stress or bad ecological status for the Radovishka River 4, Stara River 2 and Vodochnica River. The findings of this study contribute to the process of implementing macroinvertebrates as a mandatory component in futuremonitoring studies in the Republic of North Macedonia.