166
A.R.D. Stebbing . R.I. Willows
carbons (Addison 1992). The induction of imposex in marine gastropods has been
found to be specific enough that the degree of imposex is used as a surrogate for chemical analysis to monitor TBT pollution (Gibbs et al. 1966).
Biological indices of water quality allied to the distribution of chemical contaminants may provide correlative evidence of causality, when applied along a relatively
simple pollution gradient but such evidence is rarely adequate for management action.
Those biological techniques that indicate the class of contaminants responsible have
an important role, especially where they are as specific as imposex in gastropods. The
technique with greatest scope for application is the toxicological interpretation of tissue burdens with the aid of QSARs. Thus, biological effects techniques that enable
chemical effort to be focussed on establishing causality where there is demonstrable
pollution, offer the most cost-effective approach to monitoring water quality.
\Of those techniques currently available, imposex in gastropods is unique as a specific index of organotin pollution (see Section 8.6.2), while EROD induction indicates
exposure to organic contaminants (see Section 8.5.2). The use of QSARs and tissue contammant concentration-response relationships allied to scope for growth in mussels
(Widdows et al. 1990) provides a toxicological interpretation of observed reductions
in physiological (energetic) health terms of contaminant tissue burdens (see Section 8.5.4); an approach that could be extended to other species. Similarly the use of
liquid-solid extraction technology for the selective extraction and concentration of
different classes of contaminants (Bening et al. 1992) has potential, when linked to water
quality bioassay techniques, as an aid to establishing causality, but has not yet been
used operationally.
The generality of biological techniques. The lower the level of biological organisation at which a technique measures contaminant effects, the more likely it is to have
generality of application and comparability, since organisms resemble one another more
closely at lower levels. Thus genetic, biochemical and cellular indices, collectively referred to as biomarkers may be used effectively in organisms as diverse as fish and
molluscs. Indices at subcellular or cellular levels may usefully indicate specific classes
of contaminants due to adaptive metabolic responses to them, but those at the
organismallevel are,more integrated and relevant to management issues. However, the
organismal significance of toxic effects or responses at lower levels has rarely been clear.
W'hQe techniques may be transferred between taxa, there remain difficulties in relating the results of indices at different levels of biological organisation, although advances
have been made (Moore 1992; Willows 1994; Goss-Custard and Willows 1996).
More important is whether indices of toxicity in one or a few organisms can be used
to indicate the biological quality of different habitats, the health of ecosystems or the
North Sea. Clearly, no single species can adequately represent a community of species
occupying a single habitat, since the routes by which toxins become biologically available vary, as do the expressions of different mechanisms of toxic actions likely in different taxa (neurotoxin, respiratory inhibitor, genotoxin, endocrine mimic). Thus, a suite
of suitable species representative of different taxa from the plant and animal kingdoms
is essential in establishing an EQS. Toxicological data from algae and/or macrophytes,
arthropod (e.g. crustacean), non-arthropod (e.g. mollusc), fish are considered necessary (Zabell, pers. comm.). However, additional species representative of different habitats, and ecological niches are desirable, since c{)ntaminant behaviour will result in the
A.R.D. Stebbing . R.I. Willows
carbons (Addison 1992). The induction of imposex in marine gastropods has been
found to be specific enough that the degree of imposex is used as a surrogate for chemical analysis to monitor TBT pollution (Gibbs et al. 1966).
Biological indices of water quality allied to the distribution of chemical contaminants may provide correlative evidence of causality, when applied along a relatively
simple pollution gradient but such evidence is rarely adequate for management action.
Those biological techniques that indicate the class of contaminants responsible have
an important role, especially where they are as specific as imposex in gastropods. The
technique with greatest scope for application is the toxicological interpretation of tissue burdens with the aid of QSARs. Thus, biological effects techniques that enable
chemical effort to be focussed on establishing causality where there is demonstrable
pollution, offer the most cost-effective approach to monitoring water quality.
\Of those techniques currently available, imposex in gastropods is unique as a specific index of organotin pollution (see Section 8.6.2), while EROD induction indicates
exposure to organic contaminants (see Section 8.5.2). The use of QSARs and tissue contammant concentration-response relationships allied to scope for growth in mussels
(Widdows et al. 1990) provides a toxicological interpretation of observed reductions
in physiological (energetic) health terms of contaminant tissue burdens (see Section 8.5.4); an approach that could be extended to other species. Similarly the use of
liquid-solid extraction technology for the selective extraction and concentration of
different classes of contaminants (Bening et al. 1992) has potential, when linked to water
quality bioassay techniques, as an aid to establishing causality, but has not yet been
used operationally.
The generality of biological techniques. The lower the level of biological organisation at which a technique measures contaminant effects, the more likely it is to have
generality of application and comparability, since organisms resemble one another more
closely at lower levels. Thus genetic, biochemical and cellular indices, collectively referred to as biomarkers may be used effectively in organisms as diverse as fish and
molluscs. Indices at subcellular or cellular levels may usefully indicate specific classes
of contaminants due to adaptive metabolic responses to them, but those at the
organismallevel are,more integrated and relevant to management issues. However, the
organismal significance of toxic effects or responses at lower levels has rarely been clear.
W'hQe techniques may be transferred between taxa, there remain difficulties in relating the results of indices at different levels of biological organisation, although advances
have been made (Moore 1992; Willows 1994; Goss-Custard and Willows 1996).
More important is whether indices of toxicity in one or a few organisms can be used
to indicate the biological quality of different habitats, the health of ecosystems or the
North Sea. Clearly, no single species can adequately represent a community of species
occupying a single habitat, since the routes by which toxins become biologically available vary, as do the expressions of different mechanisms of toxic actions likely in different taxa (neurotoxin, respiratory inhibitor, genotoxin, endocrine mimic). Thus, a suite
of suitable species representative of different taxa from the plant and animal kingdoms
is essential in establishing an EQS. Toxicological data from algae and/or macrophytes,
arthropod (e.g. crustacean), non-arthropod (e.g. mollusc), fish are considered necessary (Zabell, pers. comm.). However, additional species representative of different habitats, and ecological niches are desirable, since c{)ntaminant behaviour will result in the