Diel drift of Chironomidae in a large lowland river (Central Poland)

Abstract

The diel drift patterns of Chironomidae larvae were investigated in a seventh order section of the Warta River (Central Poland) over two diel cycles during May 1989. Three nets (mesh size 400 pro) were installed in a cross section of the Warta River.The estimated drift density was low, but was comparable to that calculated for other large rivers. Spatio-temporal fluctuations in abundance and composition of macroinvertebrate drift, including Chironomidae, were observed with the highest density of drifting macrobenthos recorded near the depositional bank of this river. The ratio benthosdrift indicated differing propensities for of the older instars of a given chironomid taxon to drift. Orthocladiinae larvae were the most abundant subfamily of Chironomidae in drift but not in benthos, reaching up to 73% of the total drifting chironomid larvae. More taxa but fewer individuals (about 20% of the chironomid larvae collected) belonged to the tribe Chironomini, the dominant group in benthos.

Determinants of chironomid species richness in mid-European temperate rivers – Environmental factors, regional influences, diversity, and seasons

“…Drift of larvae [94,95], which is a method of downstream colonisation, is the only limnic method of dispersal. This method may have changed species number in given seasons in our research, in particular in winter (when the highest RSR occurred), in which immigration with drift may have been higher than the disappearance of species due to eclosion.…”