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animals chronically exposed in the field to different anthropogenic contaminants (Weis et
al. 2001; Perez and Wallace 2004; Kalman et al. 2009).
In fish, reproductive success depends on various complex behaviors. Underlying neu-
ral and hormonal mechanisms are relatively well known (Adkins-Regan and Weber in
Dell'Omo 2002), but little information is available concerning dysfunctions resulting
from the presence of potentially toxic chemicals in the environment (Table 10.1). Scott
and Sloman (2004) have reviewed available data about nest building, courtship behaviors,
spawning site selection, and nonreproductive social behaviors such as aggression, and
formation and maintenance of hierarchies. Again, there is a long and diverse list of met-
als and organic contaminants that are able to impair such complex behavioral patterns.
Migratory activity, which has a key role in the biology of salmonids, may be impaired by
exposure of Atlantic salmon (
Salmo salar
) smolts at environmental doses of the pesticide
atrazine (Moore et al. 2007).
10.4 Ecological Relevance of Behavioral Biomarkers
10.4.1 Environmental Realism of Behavioral Impairments
At sublethal doses, defense mechanisms are functional, and under these conditions,
ecotoxicity tests seem more representative of effects due to chronic exposure in the
field. Similarly, the duration of experiments can have a crucial influence on behavioral
responses, depending on whether detoxification mechanisms have had enough time to be
induced or not. Thus, several authors have reported that food consumption was initially
reduced in the presence of various metals but partial or total recovery occurred within 3
weeks, suggesting the induction of compensatory mechanisms such as metallothionein
induction (Bryan et al. 1995 and literature cited therein). On the other hand, in polychaetes
Hediste (Nereis) diversicolor
exposed for 96 h to reference sediments and sediments from
contaminated sites, a depletion of feeding rates has been shown despite compensatory
mechanisms functioning, although apparently insufficiently to eliminate all the contami-
nants' effects, particularly oxidative stress (Moreira et al. 2006a).
With the aim of increasing environmental realism, Riddell et al. (2005) have examined
behavioral responses to sublethal cadmium doses in an experimental food web. In juve-
nile fish (
Salvelinus fontinalis
), the efficiency of prey capture was impaired at doses (0.5 μg
L
-1
) nearing the Canadian standard for the protection of aquatic life (0.2 μg L
-1
). This com-
parison was based on nominal concentrations of cadmium added in experimental units.
An additional step toward more realism involves considering the chemical speciation of
dissolved metals that governs their bioavailability and hence toxicity (Fournier et al. 2004;
Green et al. 2010; Meyer and Adams 2010). This is particularly important for estuarine
species since free metal ion concentrations often depend on salinity, particularly in the
case of cadmium. Sublethal concentrations of cadmium as
Cd
(aq)
2+
(0.5 and 1.0 μg L
-1
) were
tested on the estuarine mysid crustacean
Neomysis integer
(Figure 10.4). Even at the low-
est concentration, swimming behavior was impaired with fewer specimens being able to
move forward into the current at stream velocities (3-9 cm s
-1
) typical in their natural
habitat. Hyperbenthic behavior was also modified since contaminated individuals were
more numerous in the water column than their nonexposed conspecifics. The effective
concentration of 0.5 μg L
-1
was within the order of magnitude of concentrations found in
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