IMPACT OF HEAVY-METALS ON BENTHIC OLIGOCHAETE COMMUNITIES IN THE RIVER ILL AND ITS TRIBUTARIES

The aim of this research is to describe the impact of heavy metals con taminating sediments on oligochaete communities Sediments were collect ed three times (June, August, October 1991) for chemical and biologica l analyses in 15 sites situated in the river Ill and its tributaries ( Rhine Basin, France). The sediments are characterized by high contents of heavy metals, mainly Hg, Cu, Cr, Pb, Zn from below the city of Mul house. The majority of sediments are heavily loaded with organic matte r and organic micropollutants are also present Oligochaete communities are rich in species. However five species only, considered as polluti on-tolerant or opportunist, are significantly present and abundant. Th e percentages of Tubificidae without hair setae are positively related to heavy metal contents of the sediments, and the percentages of Tubi ficidae with hair setae are negatively related. Several species such a s N. communis, N. barbata, D. digitata and Bothrioneurum sp. are consi dered as tolerant to heavy metals; on the contrary L. claparedeanus, L . udekemianus, Stylodrilus sp. and S. josinae are considered as intole rant. The reproductive strategy of oligochaetes in contaminated areas and the role of organic matter are discussed. Several recommendations are given for the rehabilitation of the investigated sites.