History of Biomarkers - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 33

Simplicity of implementation

Readibility

PCA IBR Expert-system

Flexibility of use

Correctness of the diagnosis without a priori knowledge

FIGURE 2.4
Synthetic comparison of three tools of integration of the responses of the battery of biomarkers in aquatic organ-
isms. (Adapted from Guerlet, E., PhD thesis, University of Metz, France, 2007.)

The authors describe the profile of biomarkers (MTs, CAT, GST, AChE) along a gradient
of pollution. The expert system selects as a guide parameter the biomarker that shows the
highest sensitivity to stress, and interprets the other data in light of the alteration level
reached by the guide parameter. More precisely, Viarengo et al. (2007), on the basis of the
work of Dagnino et al. (2007), proposed a two-tier approach to assess the level of pollutant-
induced stress syndromes in sentinel organisms. The LMS assessed either by neutral red
retention or by a histochemical technique, provides a robust Tier 1 screening biomarker for
environmental impact assessment. Tier 2, constituted by biomarkers of genotoxicity and
by biomarkers revealing an exposure (MTs, AChE, EROD, MXR, transport activity, etc.),
is used only for animals (mussels) sampled at sites in which LMS changes are evident,
and there is no mortality. Then, the above-mentioned expert system is used. However,
Guerlet (2007) notes that there is no parallel integration of the physicochemical data, and
that for this tool an overestimation of the effects is also observed when there is redun-
dancy between biomarkers.
Figure 2.4, adapted from Guerlet (2007), synthesizes the use of PCA, IBR, and the expert
system in the integration of the battery of biomarkers in aquatic organisms. The compari-
son between different ways of treating the data shows that from PCA to the expert system,
simplicity of implementation and readability increase. On the contrary, flexibility of use
and correctness of diagnosis without a priori knowledge decrease.

2.6 Conclusions
It is known that toxicity resulting from pollutant exposure appears at the subcellular level
before being observed at individual or population level. The relevant use of biomarkers