On the use of Arion ater to biomonitor environmental pollution by Cd, Cu, Fe, Mn and Zn, with a special insight into the population variability.

The suitability of Arion ater as a biomonitor of Cd, Cu, Fe, Mn and Zn was assessed. Individual specimens were collected from 22 sampling sites. Slugs from 3 of the sites were analysed individually, whereas the slugs from the other sites were pooled to make a composite sample for each site. The tissue burdens did not differ between individuals from contaminated and uncontaminated sites, and there was no gradient of bioaccumulation of any of the elements in the surroundings of the smelter. Analysis of the individual specimens from the 3 sites revealed very high coefficients of variation for the metal concentrations. As a result of the high level of variation, large numbers of slugs are required to produce a low error in characterizing the mean concentration at each site. Furthermore, as a consequence of the similar mean concentrations and high variability, large numbers of samples are needed to detect significant differences between pairs of sites.