Análisis comparativo de la estructura de las poblaciones de quironómidos en la cuenca del río Órbigo (León)

Abstract

The composition of the chironomid populations along the rivers of the Órbigo basin (León, Spain) beginning from larval stage has been analyzed. Chironomid larvae were collected using a hand-net of 250 pn mesh. Forty-two sampling sites were established in the órbigo basin. They were sampled seasonal during 1987. Thirty-one genus chironomids have been found, being able to identified 16 species. The diversity variations and its components have been analyzed, at the same time that the dominant and the heterogeneity. The affinity has been calculated with the semiquantitative similarity index. This index showed the groups characteristics on base to the physico-chemical conditions of the water. The diversity reached the biggest complexity in the spring and the smallest in the winter, The heterogeneity is high in the basin, except in some cases which heve been affected by the homogeneous characteristics of the bottom river. The winter offers a low affinity, however it defines clearly the river plots. In spring, the groups are not much homogeneous, the most of them collected the middle and the end river plots. In summer, there is a mix of the sampling sites, crowding around tolerant taxa. In autumm is achieved a recuperation of the water quality forming groups due to the presence of intolerant or relatively intolerant taxa to the contamination.