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age) has been also recognized as a confounding factor for instance in polychaetes (Durou et
al. 2007), amphipods (Xuereb et al. 2009b), and bivalves (Fossi Tankoua et al. 2011). In crus-
taceans, the life cycle stage must also be taken into account (Hoguet and Key 2007).
Nevertheless, most of these confounding factors may be controlled with an appropriate
sampling strategy and mastered by using a careful evaluation of sources of fluctuations.
Evidence is provided by the series of data obtained during a 2-year survey following the
wreck of the tanker
Erika
in the Loire estuary, France, which allowed the determination
of the background response level of the AChE in mussels (
Mytilus galloprovincialis
) and
the evaluation of the neurosuppressive effects of oil spillage on the mussels (Burgeot et al.
2010). A model of classification was designed from these results, which seems to be very
promising for future monitoring initiatives in the Coordinated Environmental Monitoring
Programme (CEMP) (monitoring under the OSPAR Joint Assessment and Monitoring
Programme where the national contributions overlap and are coordinated through adher-
ence to commonly agreed monitoring guidelines, quality assurance tools, and assessment
tools) and in the European Marine Strategy Framework Directive.
4.2.4.2 Linking Neurotoxic Effects and Behavioral Impairments
Among physiological mechanisms inducing behavioral impairments (Chapter 10), the
inhibition of neurotransmitters is well documented in aquatic organisms as a result of
many studies dealing with the toxic effects of pesticides (Tables 4.1 and 4.2).
In the endobenthic worm
Hediste (Nereis) diversicolor
, exposure to contaminated sediments
(both in the laboratory and in
in situ
tests) induced a depletion of food uptake whereas
AChE activity was not affected (Moreira
et al. 2006). In addition to sublethal effects on
stamina in some estuarine fish in association with brain AChE inhibition levels reported
by Fulton and Key (2001), temporary loss of hierarchy in food uptake (in the trout
Salvelinus
fontinalis
), behavioral deficiency (in the Mediterranean fish
Serranus scriba
), and increased
vulnerability to predation (in the Atlantic salmon
Salmo salar
) have been reported as con-
sequences of exposure to cholinesterase-inhibiting insecticides (Zinkl et al. 1991). In the
freshwater fish
Channa punctata
, exposure to the neurotoxin endosulfan induced decreases
in AChE activity and concentrations of serotonin (5-HT) associated with changes in sur-
facing behavior (Gopal et al. 1985). Dopamine was also affected, differently depending on
the level and the duration of exposure.
There are suspicions that contaminants, other than pesticides, which cause neurotoxic-
ity, could also alter different aspects of behavior. Commonly used pharmaceuticals (the
β-adrenergic receptor blocker propranolol or the anti-inflammatory drug paracetamol)
alter gill AChE activity (and other biochemical responses) and feeding rate in mussels but
at doses not likely to be encountered in the marine environment (Solé et al. 2010).
4.2.4.3 Linking AChE Activity Inhibition and Population Effects
Because cholinesterase-inhibiting pesticides disrupt neuromuscular signaling, reduction
in performance seems to be a logical outcome of this biochemical disruption at the organ-
ism level (Hopkins and Winne 2006). Several studies have examined fitness-related traits,
growth and reproduction impairments, and survival in aquatic organisms exposed to such
pesticides but effects on AChE activity were only implicit, not measured (Andersen et al.
2006; Hopkins and Winne 2006). More interestingly, several studies examined concomi-
tantly effects at different levels of biological organization in order to highlight implications
for population dynamics (Duquesne 2006; Gaworecki et al. 2009; Duquesne and Küster 2010).
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