A multimetric macroinvertebrate index for the assessment of the ecological status of Lithuanian rivers

Abstract

We present the design of the Lithuanian River Macroinvertebrate Index (LRMI) – a Water Framework Directive compliant method for assessing the ecological status of Lithuanian rivers that primarily addresses the eutrophication pressure. It is a multimetric index that averages the ecological quality ratios of two conventional metrics – the Danish Stream Fauna Index (DSFI) and the Average Score Per Taxon (ASPT) – as well as the two newly assembled metrics – the taxonomic richness of Diptera, Ephemeroptera, and Plecoptera (#DEP) and the difference between the pooled relative abundances of Ephemeroptera, Heteroptera, and Plecoptera versus Crustacea and Hirudinea (%EHP–%CrHi). The LRMI showed significant correlations with hydrochemical indicators of nutrient enrichment in the national river dataset. Moreover, our analysis showed its potential sensitivity toward hydromorphological alterations of the riverine habitats. Finally, the results indicated that further developments concerning minor type-specific adjustments of the currently set ecological class boundaries may be beneficial to the new method.