Environmental Engineering Reference
In-Depth Information
6
Biomarkers in integrated ecotoxicological
sediment assessment
Mark G.J. Hartl
1
1
Centre for Marine Biodiversity and Biotechnology, School of Life Sciences, Heriot-Watt
University, Edinburgh, UK
6.1 Introduction
Biomarkers are powerful tools for detecting sublethal
exposure to a given substance or a complex chemical
mixture, enabling the evaluation of more subtle
effects on organisms and can be applied as an early
warning system. Biomarkers can be loosely catego-
rized as those of exposure, effect, and susceptibility.
A biomarker of exposure indicates that an organism
has come into contact with a contaminant or con-
taminant mixture, and can give qualitative and quan-
titative estimates of bioavailability (Schlenk 1999;
Chambers
et al.
2002), but provides little information
about the cause of the observed interaction. Causality
can be established by applying biomarkers of effect
that relate to a specifi c contaminant or contaminant
class through a well-described mode of action. As the
response to exposure may depend on various envi-
ronmental and physiological conditions, it will not
be identical in all individuals of the same species
reducing the dose-response resolution. Therefore, in
addition to biomarkers of exposure and effect,
biomarkers of susceptibility are required to help iden-
tify areas of uncertainty that may occur between the
exposure to a contaminant and the emergence of
clinical symptoms (Schlenk 1999).
The use of biomarkers in aquatic ecotoxicology
has traditionally been limited to the exposure of
sentinel organisms or
in vitro
test systems to pollut-
ants in aqueous solutions or suspensions. These
approaches have been instrumental in providing
guidelines for legislative measures aimed at reducing
the impact of anthropogenic pressure on marine and
freshwater environments. In recent years, however,
the relative improvement of water quality in many
areas and the recognition that sediments may serve
not just as sinks but also as secondary sources for
many persistent chemicals (Harris
et al.
1996), has
shifted the focus of ecotoxicological studies toward
After the publication of
Silent Spring
by Rachel
Carson (1962), which saw the fi rst attempt to sepa-
rate environmental toxicology from classical toxicol-
ogy, Truhaut (1977) introduced the term “ecological
toxicology” or “ecotoxicology” to describe the toxi-
cological impact of environmental contaminants in
the ecosystem, beyond the level of the individual
organism. This was defi ned further by Chapman
(2002) to include toxicity on all levels of biological
organization and the environmental fate of
contaminants.
Environmental contaminants have been linked to
population-level variations of sensitive keystone
species, whose reduced vitality or removal can erode
community structure and potentially reduce diversity
and stability (Paine 1966). Such impacts on higher
levels of biological organization only become appar-
ent when a signifi cant part of the population is
already affected. Therefore, much effort has been
devoted to establishing protocols for monitoring
more subtle sublethal effects on various levels of
biological organization. These are referred to as
biomarkers for fl agging up potential adverse anthro-
pogenic impacts at an early and manageable stage.
A biomarker, as defi ned by Depledge
et al.
(1993),
is “… a biochemical, [genetic] cellular, physiological
or behavioural variation that can be measured in
tissue or body fl uid samples or at the level of the
whole organism (either individuals or populations),
that provides evidence of exposure and/or effects of
one or more chemical pollutants (and/or radiation)”.
