Original paper

Emergence patterns of lotic Chironomidae (Diptera: Nematocera) in southern Finland and the use of their pupal exuviae in river biomonitoring

Raunio, Janne; Paasivirta, Lauri

Abstract

Chironomidae (Diptera: Nematocera) pupal exuviae were sampled from several medium to large sized rivers in southern Finland. In addition to pupal exuvial samples, two rivers and one stream were sampled by collecting adult chironomids. Our purpose was to determine the timing and extent of the emergence period of common (abundant and wide-spread) lotic chironomid species in southern Finland. We describe the emergence patterns of 195 chironomid taxa (26 % of the chironomid fauna recorded from Finland). A major proportion of species richness was accounted for by the sub-families Chironominae and Orthocladiinae. Many taxa considered intolerant of pollution emerged mainly in spring (May). On the other hand, tolerant taxa such as Chironomus and Glyptotendipes species emerged during an extended period in summer (June-August). During autumn (September), the majority of emerging chironomids were already detected in preceding samples, thus representing species with more than one generation per year. For biomonitoring of boreal rivers, a species-level tolerance classification of chironomids along the oligotrophy-eutrophy gradient is proposed.

Keywords

chironomidaeemergence patternsboreal riversbiomonitoringpupal exuviae