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the physicochemical forms of storage of the accumulated metals (Evtushenko et al. 1986;
Couillard et al. 1995b; Mouneyrac et al. 1999). In the same way, the condition indices of the
transplanted animals tend to get closer to those of the resident individuals, and to move
away from those of individuals remaining at the site of origin, as, for example, for oysters
transplanted from the Bay of Bourgneuf to the Gironde estuary, and conversely (Geffard,
personal communication). Using double transplantations of mussels ( Mytilus galloprovin-
cialis ) between a polluted harbor area and in a weakly impacted site, Regoli et al. (2004)
were able to associate several biomarkers of oxidative stress [antioxidants, total oxyradical
scavenging capacity (TOSC)] and changes in cellular structures (integrity of the DNA, lyso-
somal stability), and observed that not all have the same periods of change, and that the
transplantation itself causes an antioxidant response in the initial phase of the experiment.
Camus et al. (2004), carrying out the same type of experiment to estimate the impacts of the
anthropological activities in the Venice urban zone and in various points of Venice lagoon,
also demonstrated the influence of transplantation on biomarkers of oxidative stress. Camus
et al. (2004) indicated that 2 weeks are necessary to observe significant differences in TOSC
between mussels transplanted into the urban zone and those at the control site, whereas the
return to the initial values in the control group is realized only after 4 weeks.
7.2 Concept of Ecosystem Approach
Any selection of a sentinel species has to be justified by a recognized link to the structure
or the functioning of the ecosystem under surveillance, so that its use brings “a part of
the complete puzzle,” integrating the interrelations between the various constituents of
the studied system. In recent years, several authors (Chapman 2002; McCarty et al. 2002;
Galloway et al. 2004; Tabor and Aguirre 2004; Hagger et al. 2009) have expressed regret that
the selection of sentinel species has been based more on anthropomorphic criteria than
ecological ones. For Chapman (2002), the species used have too often been selected for their
ease of collection and manipulation or breeding in laboratory, whereas their roles in the
ecosystem (place in the food chain, the structure of the community, and their functions in
the ecosystem) have been neglected. In order to introduce more ECO into ECOtoxicological
programs, in natural environments as in the laboratory, it is advisable to study biomarkers
in sentinel species that are more representative of the ecosystem. In a project entitled “The
ECOMAN project,” Galloway et al. (2004) recommend a multispecific approach where the
species are selected on the variety of their habitats (rocky, sandy, muddy) in estuarine
or coastal environments and of their food strategies (filter- or deposit-feeders, grazers
or predators). Table 7.2 shows the various representative organisms of the main phyla of
invertebrates that are easy to identify and are widely represented in the coastal zones of
Northern Europe, selected for their biological and ecological complementarity.
However, if this ecological approach is indispensable, it is not sufficient as pointed out
by Chapman (2002), who recommends focus on keystone species.
7.2.1 Keystone Species
Species interact with numerous constituents of the ecosystem. Where there are no ecologi-
cal equivalents present, the disturbance of a species, such as by contaminant exposure, can
cause deleterious modifications of the quantitative structure of the community, perturb
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