Hydrobiologia 392: 73–80, 1999. H.L. Golterman (ed.), Sediment–Water Interaction 9. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 73 Impact of arsenic and antimony contamination on benthic invertebrates in a minor Corsican river Christophe Mori 1 , Antoine Orsini 1 & Christophe Migon 2,∗ 1 Laboratoire CEVAREN, Universit´ e de Corse, B.P. 52, Corte, 20250, France 2 Laboratoire de Physique et de Chimie Marines, Universit´ e Paris 6, INSU CNRS, La Darse, B.P. 8, 06230 Villefranche-sur-mer, France Tel: [+33] 0 4 95450030; E-mail: mori@univ-corse.fr ( ∗ author for correspondence) Key words: As, Sb, macroinvertebrates, stream Abstract The chemical and biological characteristics of a Corsican river that drains contaminated waters and sediment from an abandoned realgar mine were studied. The concentrations of pollutants such as As and Sb were found to be notably high. For example, in the Presa River, downstream the realgar mine, the mean As concentrations in the water and in the sediment were 3010 μg1 −1 and 9450 μgg −1 respectively. Species richness and abundance of benthic invertebrates decreased downstream the As mine. The disappearance of oligochaetes, leeches and a rarity of mayfly populations have been evidenced. On the contrary, a large increase in species belonging to stoneflies and gastropods was found. Some species like Baetis cyrneus, Ephemerella ignita, Sericostoma clypeatum and Ibisia marginata were more sensitive to As and Sb concentrations while others species like Ancylus fluviatilis, Isoperla insularis, Hydropsyche cyrnotica, Caenis luctuosa and Silonella aurata were less sensitive. The benthic invertebrates show different reactions in this contaminated environment, which could be explained by their feeding behaviours and certain morphological characteristics. Introduction A decline in biodiversity of benthic communities has often been related to metal pollution (Clements, 1994; Gibert et al., 1995; Kiffney & Clements, 1996; Hill et al., 1997), but As and Sb are not often studied (in contrast to Zn, Cu, Cd). Arsenic, and to a lesser extent, antimony, are important environmental pollutants related to anthro- pogenic activities. Large quantities of arsenic com- pounds are released into the environment, particularly through mining operations and biocidal products; Sb chemistry is very similar to that of As (Migon et al., 1995). As and Sb bioaccumulation has been demonstrated for aquatic invertebrates by Sanders & Cope (1968), Schuth et al. (1974) and Irgrolic et al. (1977). Toxicity and bioaccumulation of arsenic are strongly dependent on its chemical state, in particu- lar its chemical speciation (Moore & Ramamoorthy, 1984; Phillips, 1990). Trivalent and pentavalent in- organic ionogenic forms of As can exist dissolved in natural waters, as well as organic forms. According to Spehar et al.(1980) the inorganic form is the most toxic and its bioaccumulation is more significant. As (III) is considered to be more toxic than As (V ) (Fergusson & Gavis, 1972; Shannon & Strayer, 1989). As (III) probably reacts with SH groups in pro- teins while As (V ) , chemically similar to phosphate, is quickly assimilated by microorganisms (Elinder, 1984) and may inhibit primary production, espe- cially if the external phosphate concentration is low (Sanders, 1979). The toxicity of antimony is less well documented. The relative toxicity of Sb (III) and Sb (V ) is less known than that of As, but it seems that the oxidation state is a factor influencing excretion rate: Sb (III) should be eliminated less quickly than Sb (V ) (Migon et al., 1995). Since the chemistry is similar to that of As, fate and effect may also be comparable.