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562 F. Cubadda et al. / Chemosphere 45 (2001) 561±569
et al., 1992; Malea et al., 1994). In a number of these Fig. 1. Experimental area and sampling stations. 1. Punta
investigations on the metal pollution of coastal sites and Sottile; 2. Previto; 3. Cala Azzurra; 4. Cala Rossa; 5. Harbour.
estuaries, various members of the indigenous biota have
been employed to evaluate the bioavailable levels of stations to test the response of the selected species to
metals in the marine environment. Some molluscs, no- more stressed environmental conditions.
tably mussels (Mytilus galloprovincialis Lam.) and oys-
ters (Ostrea edulis L.), have been frequently selected for At every sampling station up to 40 individuals of
monitoring purposes in such surveys (Martincic et al., each species were handpicked in the tidal zone, accord-
1984; Bargagli et al., 1985; Mikac et al., 1985; Ozretic et ing to their availability (not all species were found at all
al., 1990; Zatta et al., 1992; Catsiki et al., 1994). The use locations). As far as possible, large size ranges of mol-
of bivalve or gastropod molluscs looks attractive as luscs were collected to allow subsequent generation of
these organisms take up metals from all environmental meaningful size±concentration regressions and compar-
compartments (i.e., from the aqueous medium and ± ison between locations by analysis of covariance (AN-
through ingestion ± from food and inorganic particulate COVA). Data about shell sizes and corresponding
material) and heavily concentrate them (Phillips, 1977). weight ranges are reported in Table 1.
Moreover, these animals are sessile or sedentary, avail-
able all year long and easy to sample. Organisms were transported to the laboratory in pre-
cleaned polyethylene bags and allowed to depurate for
The gastropods of the genera Monodonta (snails) and two days in ®ltered seawater collected at the same sta-
Patella (limpets) are among the commonest inhabitants tion. Then shell sizes were measured and the soft tissues
of rocky shores in the whole Mediterranean basin. were dissected using plastic equipment, rinsed brie¯y (to
Owing to their widespread distribution over coastal ar- avoid any possible metal loss) with Milli-Q water, and
eas, these herbivorous molluscs are often found in sites frozen pending analysis.
where mussels and oysters are absent. However, there is
a lack of information on their ability to concentrate 2.2. Analysis
trace metals and their accumulation patterns, the few
studies available referring to contaminated sites in re-
stricted geographical areas (Bargagli et al., 1985; Nico-
laidou and Nott, 1990; Ozretic et al., 1990; Nicolaidou,
1994; Kozanglou and Catsiki, 1997).
In the present study trace metal concentrations in
four species belonging to the genera Monodonta and
Patella collected at uncontaminated sites were investi-
gated with the aim of obtaining background levels for
performing intraspeci®c comparison within the Medi-
terranean area. Secondly, the responses of the molluscs
in a contaminated site and the eect of body size upon
metal concentration were studied in order to gain more
information on the possible use of the selected species as
biomonitors for the Mediterranean area.
2. Materials and methods After thawing each organism was weighed, trans-
ferred into te¯on vessels together with a mixture (5 + 2
2.1. Sampling and sample preparation ml) of concentrated HNO3=H2O2 (ultrapure grade) and
digested in a microwave oven. Separate dry-weight de-
Individuals of Monodonta turbinata Born, Mono- termination was performed on 10 individuals from each
donta mutabilis Philippi, Patella caerulea L., and Patella location by oven drying at 105°C until constant weight.
lusitanica Gmelin were collected in May 1997 at ®ve The mean values of wet weight/dry weight ratio are re-
stations located along the coast of Favignana Island ported in Table 1.
(37°56HN: 12°19HE), Sicily, Italy (Fig. 1). This small is-
land, the major of the Egadi archipelago, is largely un- Ten to thirty molluscs from each station were ana-
aected by human activities and lacks any industrial lysed individually. Cadmium, chromium and lead were
settlement. The local harbour, the only site which ap- determined by graphite furnace atomic absorption
peared to be contaminated by naval trac emissions and spectrometry (GFAAS). NH4H2PO4 was used as matrix
domestic waste discharge, was included in the sampling modi®er for Cd and Pb, and Mg
NO32 for Cr. At least
duplicate determination of each sample was carried out
and the standard addition method was used. Copper and
