Efecto de la contaminación y la regulación del caudal sobre la comunidad de macroinvertebrados bentónicos del tramo bajo del río Larraun (norte de España)

Abstract

The macroinvertebrate community in the lower reach of the Larraun river (N Spain) was studied in spring and summer 1998. This area is affected by the operational cycle of a small hydroelectric power plant and the urban and industrial area of Irurtzun. Abundance and benthic community structure changed in the river as a consequence of these human impacts. Chironomids were dominant organism in the altered points of the river, while gammarids and mayflies (Baetidae and Heptageniidae to a smaller extent) were more numerous in non altered river reach. Moreover, collectors were the main functional group downstream Irurtzun. Abundance of benthic inverte- brates decreased in the regulated reach of the river and downstream the locality of Irurtzun.