Impact d'une perturbation polluante d'origine organique sur les populations et les communautés d'invertébrés benthiques et en dérive d'une rivière méditerranéenne, le Tavignano (Corse)

Abstract

This paper deals with effects of a perturbation due to organic pollution on macroinvertebrates communities in a mediterranean river of central Corsica. The study was based chiefly on consideration of benthic and drift samples. The effects of an heavy pollution were much the same as described for other streams, but reactions of several taxa seemed to be less marked. In the most polluted area of this speedy well oxygenated river, oligochetae, molluscs, chirono-mid larvae showed a marked increase in density but never occurred in enormous numbers. In this corsican river, the communities of the lentic habitats were more affected by the organic pollution than the lotic ones. Drift samples showed clear reactions to organic pollution : decreasing drift diversity and density of aquatic organisms, increasing drift density of emerging fauna, disappearing oligotrophia species. Drift communities were more closely related to benthic lotic communities than to lentic ones. We suggest that in this river type, the biotic index method applied on benthic samples cannot detect biological consequences of severe organic pollution, although it gives good results with drift samples which will be considered as indicators of river quality.