Response of Chironomids to Key Environmental Factors: Perspective for Biomonitoring

Chironomids are the species richest family among macroinvertebrates and are often used as indicators of ecological condition in inland waters. High taxonomic expertise is needed for identification and new species are still described even in the well-known West Palaearctic region. Data were filed in a Microsoft Access relational database and analysed using the R environment. Our database comprises data on Chironomid species collected in rivers and lakes in Italy and some other European countries over a period of about 50 years, often associated with physical-chemical data, but in some cases only benthic macroinvertebrates are available with no associated environmental data. In this case, the possibility of estimating water quality with only species composition available is discussed. Traits summarizing the species response to environmental variables were evaluated, with emphasis on natural and man influenced factors: current velocity, water temperature, conductivity, dissolved oxygen, nutrients. Traits calculations was possible using the subset of database including both environmental data and Chironomid abundances. The relations between sites, species and traits were evaluated using correspondence analysis and other multivariate methods. The response of species showed an interaction among different factors, with the possibility to order species along a single environmental gradient, extending from cold running waters to warm standing waters, with few exceptions. The utility and limits of the use of ecological traits are discussed.