Variaci´ on de la comunidad de macroinvertebrados bent´ onicos en relaci´ on con la calidad de las aguas ´ A

Variability of the benthonic macroinvertebrate community in relation water quality The bentonic macroinvertebrate community at five points of the Larraun River (N Spain) was studied in spring and summer 1998 in order to analyse the changes in abundance and structure associated with water pollution and the activity of some hydroelectrical plants. The structure of the macroinverterbate community was altered as a consequence of these changes of human origin. Chironomids were dominant in the altered stretches of the river, while gammarids and mayflies were more numerous in non-altered stretches. Collectors were the main trophic group in the places with higher nutrient concentrations. The abundance of bentonic macroinvertebrates decreased in the more polluted areas and in the regulated reach of the river.