Steps towards a more efficient use of chironomids as bioindicators for freshwater bioassessment: Exploiting eDNA and other genetic tools

Abstract

• We present a synthesis of improving bioindication using chironomids. • Morphological approaches are needed to accurately delimit taxa. • Molecular biological approaches can help biomonitoring using chironomids. • Environmental DNA can inform on the diversity and distribution of chironomids. • Expression analysis can be used to detect non-lethal stressors. Chironomids are a formidable indicator taxon, as they are globally ubiquitous, can tolerate a wide range of environmental conditions, and can occur in high numbers in anthropogenically impaired environments where other indicator taxa are not encountered. Biomonitoring is frequently performed through analyzing species composition, abundance and morphology. However, these traditional approaches may be problematic, since indicator taxon morphology is often cryptic, and inadequately assigned species complexes may lead to generalized ecological tolerances. We argue that the use of chironomids in freshwater biomonitoring could be much improved if physiological responses to a given pollutant were measured in conjunction with precisely determined species, aided by molecular approaches such as is already done for some well known mesophilic and extremophile species in certain regions of the world. We explore molecular biological approaches that may prove useful for this purpose.