Conclusions: Biomarkers in Environmental Risk Assessment - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 427

a
b
c
Contaminant exposure
FIGURE 16.3
Changes in the response of biomarkers of damage (a, b) and of defense (c) as a function of the level of con-
taminant exposure. (a) Increasing response (e.g., lipofuscin lysosomal content, DNA damage). (b) Decreasing
response (e.g., lysosomal membrane stability, AChE activity). (c) Bell-shaped curve (EROD, GST, MT). (Adapted
from Dagnino, A. et al., Biomarkers , 12, 155-172, 2007.)
in Amiard-Triquet et al. 2011; Ji and Lu 2011). In the case of biomarkers of damage, the inter-
pretation is easier, even in the absence of chemical data, since the response trend has no
reversal of direction with increasing level of contaminant exposure (Figure 16.3). Even for
core biomarkers the present degree of validation is still insufficient to avoid the parallel
use of chemical analysis, an outcome that would be beneficial, particularly in developing
countries, since it would allow reduction of the cost of environmental monitoring.
In order to reinforce the ecological value of biomarkers, the choice of the biological matrix
in which they are to be determined is crucial. The selection of biological models or sentinel
species has to cope with a major problem that is the importance of any inherent variability,
between individuals as well as between species. It can be recommended to focus (1) on
the most sensitive species or life stages, the protection of which will probably ensure the
security of less sensitive species; (2) on species that have a key role in the structure and
functioning of the ecosystem; or, even better, (3) on a set of species able to represent the
different functional aspects of the ecosystem (Chapter 7).
As highlighted in Chapter 14, the cumulative effects of multiple stressors should become
a priority concern for ecotoxicologists, particularly to explore how adaptation to chroni-
cally contaminated habitats could affect the ability of populations to cope with other
stressors, particularly from the perspective of global warming.
16.4.2 Integrating Biomarkers in a Weight of Evidence Approach
Environmental quality assessments inevitably now call upon data from a variety of multi-
disciplinary sources, and the weight of evidence (WOE) approach has been developed to
combine information from these different lines of evidence (LOEs). The WOE process can,
for example, help to determine the extent of contamination or its ecological significance, and
can contribute to defining an optimal remediation program (Luoma and Rainbow 2008).
Thus, the WOE approach is being increasingly adopted within the context of ecological risk
assessments, including the quality assessment of polluted sediments, and biomarkers have
a key role to play as a contributory LOE to such ends (Chapman and Hollert 2006; Morales-
Caselles et al. 2009; Benedetti et al. 2012). For assessment of sediment quality, Chapman