Experimental study of the combined effects of pH and salinity on the bioaccumulation of inorganic mercury in the crayfishAstacus leptodactylus

Abstract

The combined effects of pH and salinity were investigated on the bioaccumulation of inorganic mercury in the Turkish crayfish Astacus leptodactylus, at the whole organism and organ levels. Effects on the ionic balance were also analysed during the acclimatization phase and after 3 and 15 days of exposure, via the direct route. The experimental protocol, based on a complete factorial design, took into account nine experimental conditions, resulting from the combination of three levels for pH (6, 7.5 and 9) and for salinity (1, 10 and 100 mM Cl-). The results showed an important Hg accumulation in the organs or tissues in direct contact with the surrounding medium, e.g. gills and carapace. The effects of the nine pH and salinity conditions were complex and variable from one organ to another. Correlations were studied between chemical species concentrations in the water (HgCl2, HgOHCl, HgCl3-,HgCl42, Hg(OH)2) and amounts of metal accumulated in the different organs. A positive correlation was found between the neutral species HgCl2 and metal accumulated in the gills and in the carapace. Perturbations of the haemolymph ionic concentrations were no significant, except for Na+ after 3 days of exposure.