Lentic chironomid performance in species-based bioassessment proving: High-level taxonomy is not a dead end in monitoring

Abstract Chironomid identification for freshwater bioassessment purposes is rarely finer than family or subfamily level. This has led to their taxonomic neglect and a lack of knowledge about their characteristics and ecology at the genus or species level, which in turn makes their implementation in bioassessment models even less appealing. The aim of this study was to object against this practice and evaluate the possibility of using chironomid assemblages solely in assessing organic and nutrient enrichment levels of lentic habitats. For this purpose, the littoral zone of 28 lentic water bodies of the Dinaric western Balkan ecoregion was sampled. Due to the scarcity of natural lakes in this region, resulting from its specific karst geology, both natural and artificial water bodies were included in this survey. Chironomids, determined mostly to species and genus level, were tested in response to variables associated with organic enrichment (dissolved organic carbon and oxygen demand measures) and nitrate concentration. A metric (Lake chironomid metric, LCM) based on 107 chironomid taxa was developed and proven to reflect organic enrichment more precisely than standard metrics that respond to organic enrichment (BMWP and different Saprobic indices). We found that the LCM strongly supports the use of chironomids with high taxonomic resolution in lentic habitat assessment, as we have shown that chironomids have the ability to improve, or even replace, already existing models for organic nutrient enrichment. We have also shown that chironomids can be used in assessing even finer levels of nitrate pollution with changes in community occurring at as low as 0.07 mgNO3−/l. This allows earlier intervention and hopefully prevention of considerable damage to the environment. We can conclude that chironomids (especially determined to species level) have great potential in monitoring of lake ecosystems.