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F. Cubadda et al. / Chemosphere 45 (2001) 561±569 567
Table 6
Concentration factorsa (mean Æ SD)Â10À3 calculated with reference to soluble and total metal concentrations in seawater
Cd Cr Cu Pb Zn
Total 6:8 Æ 2:1 1:4 Æ 0:5 6:3 Æ 1:9 0:13 Æ 0:06 4:7 Æ 0:7
M. turbinata 6:1 Æ 1:2 1:4 Æ 1:2 8:8 Æ 4:0 0:08 Æ 0:02 2:9 Æ 1:0
M. mutabilis 18:9 Æ 4:0 1:6 Æ 0:3 0:8 Æ 0:3 0:22 Æ 0:10 1:0 Æ 0:5
P. caerulea 12:2 Æ 3:0 1:2 Æ 0:1 1:2 Æ 0:5 0:17 Æ 0:07 1:3 Æ 0:4
P. lusitanica
Soluble 12:7 Æ 5:1 2:6 Æ 1:0 19:5 Æ 8:0 0:39 Æ 0:13 10:6 Æ 3:1
M. turbinata 12:0 Æ 1:6 2:5 Æ 1:2 22:3 Æ 6:3 0:24 Æ 0:03 6:8 Æ 3:2
M. mutabilis 37:5 Æ 8:7 3:0 Æ 0:8 2:6 Æ 0:7 0:70 Æ 0:22 2:3 Æ 1:1
P. caerulea 22:2 Æ 7:9 2:5 Æ 0:5 3:7 Æ 1:1 0:56 Æ 0:19 3:0 Æ 1:2
P. lusitanica
a CF CO=CSW, where CO mean concentration in the organism (lg gÀ1 dry wt) and CSW mean concentration in seawater
mg lÀ1.
the specimens collected at the harbour (station 5) were ined in this study, which showed a weak dependence of
found to contain considerable amounts of metals. The Zn tissue concentrations on body weight (i.e., similar
highest levels of Cd, Cu, Pb and Zn were recorded at this contents of Zn among individuals from the same site)
site, while Cr concentrations were similar to those ob- but dierent Cu and Zn tissue concentrations among
served in stations 3±4. These dierences in Cd, Cu, Pb individuals from dierent locations. On the contrary, the
and Zn contents were detected (and in some cases turned two species of the genus Patella showed surprisingly
out to be statistically signi®cant) even though station 5 uniform levels of copper among stations, which is con-
undoubtedly shows a lower degree of contamination sistent with the low percentage of variability explained
than severely polluted sites found in other areas of the by the factor location in Table 5. Therefore, a certain
Mediterranean. The capacity of the four gastropods regulation capability of these species for copper can not
selected in this study to detect spatial trends in metal be excluded.
bioavailability support the concept of their use for
monitoring purposes. Moreover, if the positive correla- With regard to their distribution, M. turbinata, P.
tion between metal concentration and body weight ob- caerulea, and P. lusitanica are probably among the most
served in our investigation is a general feature of these cosmopolitan shell®shes found in Mediterranean coastal
species, their power to detect dierences among loca- areas. However, M. turbinata has the considerable tax-
tions can be enhanced by proper selection of body size onomic advantage of being uniquely simple to identify,
range of the individuals during sampling. an essential requirement for a biomonitor (Rainbow and
Phillips, 1993). Moreover, laboratory studies on this
As far as net accumulation is concerned, the species species showed its ability to accumulate a number of
of the genus Patella look more suitable as biomonitors toxic metals proportionally to the concentrations in its
of Cd availability, while the species of the genus ambient water even when the levels in the aqueous me-
Monodonta oer promise for Cu and Zn. However, the dium are very high (Verriopoulos et al., 1989; Catsiki et
accumulation capacity is only a prerequisite for the al., 1993; Manelis et al., 1993). This gastropod is able to
adoption of a certain species as trace metal biomonitor. tolerate well these high concentrations of toxicants, a
As noted above, an essential feature is the ability to behaviour which could be related to the defence mech-
detect trends in metal bioavailability, i.e., to re¯ect the anisms termed MXRM (multixenobiotic resistance
environmental concentrations of a given metal without mechanism) (Kurelec, 1995; Kurelec et al., 1995).
regulating its level in the body tissues. This is a critical
point, especially as far as essential trace metals ± such as In the light of the foregoing remarks, M. turbinata
Cu and Zn ± are concerned. In fact, these metals are vital appears to be the organism with the greater potential as
components of enzymes as well as of respiratory pig- biomonitor for the Mediterranean area. Therefore, fur-
ments of marine invertebrates and metabolic require- ther research work aiming to fully clarify the actual
ments of these metals often make up signi®cant accumulation patterns of this species and to assess it
proportions of their total content in molluscs from non- robustness for routine use in marine biomonitoring
polluted environments (White and Rainbow, 1985). would be advisable.
Certain molluscs are able to regulate the body concen-
tration of these metals to an approximately constant Acknowledgements
level over a wide range of ambient availabilities (De-
pledge and Rainbow, 1990; Soto et al., 1997). This seems We thank Dr. Marco Oliverio for his aid in the
not to be the case of the two Monodonta species exam- identi®cation of the mollusc species.
