Conclusions: Biomarkers in Environmental Risk Assessment - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 426

16.4 Multidisciplinary Approach for Classifying Polluted Environments
16.4.1 Implementation of Biomarkers
The biomarkers of ecological relevance that have been reviewed in this topic have pro-
vided significant progress in the field of environmental assessment compared to the “core
biomarkers” (mainly biochemical biomarkers) described in Chapter 2. They can be very
useful for biomonitoring purposes, since they are able to reveal environmental health
impairments before massive effects occur at the level of populations or communities. They
can contribute to a prognostic risk assessment, contrary to biotic indices based on the
community structure that allow only a retrospective assessment when degradation has
already occurred.
Biomarkers of ecological relevance will also allow a classification of contaminated sites
based on the potential risk of complex mixtures of pollutants for ecosystem health, inte-
grating across total contaminant availabilities rather than relying on the concentrations of
a limited number of chemical pollutants, in effect those perceived as easy to analyze ( a pri-
ori analysis). So biomarkers are potentially of great assistance to stakeholders, for instance,
when there is a need to establish priorities for remediation campaigns (Chapter 15).
Compared to the classical biomarkers of defense or damage, they are situated at a higher
level of biological organization, but consequently they are often less sensitive. However,
for each of them, the different chapters of this topic provide many examples highlighting
significant responses observed in contaminated natural media or—in the case of labora-
tory experiments—at environmentally realistic doses.
Biomarkers of ecological relevance (Figure 16.1) are generally nonspecific biomarkers,
interestingly providing a general assessment of environmental quality, but on the other
hand, responding to a large number of chemical contaminants and even to nonchemical
stresses. However, in order to decide upon actions aimed to improve environmental qual-
ity, environmental managers need to know the substances responsible for the impaired
health status of the local biota. For this purpose, toxicity identification evaluation studies
may be designed, combining fractionation and chemical analysis of fractions obtained
from an effluent or a contaminated sediment with bioassays for the characterization of
the toxicity associated with each fraction (Amiard et al. 2009). At this stage, core biomark-
ers provide a relevant complementary approach (Figure 16.1), even though they are less
specific than initially supposed when the methodology of biomarkers was first developed
in the early 1990s; this applies even in the cases of AChE initially labeled as a specific bio-
marker for organophosphorous pesticides and carbamates, and MT, a biomarker of expo-
sure to metal contaminants. At any rate, this deficiency is now well recognized, and it is
widely admitted that the solution lies in the use of multibiomarker approaches (Chapter 2).
For certain authors, except when it has been firmly established that there is no risk pres-
ent, any detection of a biomarker response should be considered a sign of a potential, and
therefore an unacceptable, risk for organisms (the Precautionary Principle). Biomarkers
of defense are activated by their (more or less specific) inducers below a certain threshold
above which the toxicity is so high that defense mechanisms are inhibited. In the absence
of data on concentrations of contaminant chemicals in the environment or in the organisms
themselves, it is impossible to decide if the biomarker response lies in the increase phase
(when the organisms are able to tolerate that level of contamination) or in the decrease
phase (when the health of the organisms is compromised) of a bell-shaped curve as shown
in Figure 16.3 (e.g., Correia et al. 2007; Ortiz-Delgado et al. 2008; Amiard-Triquet and Roméo