Size-dependent concentrations of trace metals in four Mediterranean gastropods

In order to gain more information on the possible use of four gastropod spe cies as metal biomonitors for the Mediterranean area, the influence of body weight upon Cd, Cr, Cu, Pb and Zn concentrations was studied in specimens collected at locations with different degrees of environmental pollution. T he selected species were the marine snails Monodonta turbinata Born and Mon odonta mutabilis Philippi, and the limpets Patella caerulea L. and Patella lusitanica Gmelin. Significant differences between metal concentrations in individuals from different stations were tested by ANCOVA on log-transforme d data with log body weight as covariate. For all species a positive correl ation between metal concentrations and body weight was observed, which mean s that the largest individuals contained the highest levels of metals. The inclusion of body weight as covariate in the statistical analysis explained from 81% to 99% of the metal variability within the organisms and enabled the achievement of improvements in the detection of differences among sites . The four selected species provided a rather univocal picture of bioavaila ble metal loads at the different stations of the experimental area. Except for Cd, the metal concentrations recorded at the clean stations were found to he in the range of the lowest values reported in the literature and can be employed as useful background levels which can be referred to for intras pecific comparison within the Mediterranean area. It is concluded that in v iew of its distribution, unambiguous identification, resistance to pollutio n and accumulation patterns M. turbinata has considerable potential as a bi omonitor of trace metals over the Mediterranean. (C) 2001 Elsevier Science Ltd. All rights reserved.