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ecological consequences have been examined (Roast et al. 2000, 2001). They include an
increased predation pressure and a displacement from areas of optimum feeding that
could lead indirectly to mysid mortalities in the natural environment, called “ecological
death.” Indeed, exposure of N. integer to 1.0 μg Cd (aq)
2+ L -1 in the natural environment may
lead to mysids being completely swept from the estuary, since in experiments by Roast et
al. (2001) many cadmium-exposed mysids were unable to swim against a current as low
as 3 cm s -1 .
Prey-predator interactions have a key role in controlling the composition and productiv-
ity of communities (Pearson et al. 1981; Mesa et al. 1994; Bryan et al. 1995). Table 10.1 pro-
vides examples of impairments of behavior of predators exposed to toxicants even under
field conditions in polluted areas. For more examples, the reader can refer to reviews by
Atchinson et al. (1987) and Grue et al. (in Dell'Omo 2002). Decreased food intakes have
consequences in terms of energy budget (Chapter 11), growth, and reproduction. When
the impacted species is an important link in the food chain, this can have repercussions at
higher trophic levels. Considering prey species, fish subjected to stress may be more vul-
nerable to their predators than their nonexposed conspecifics (Mesa et al. 1994; Sandahl et
al. 2007; Kusch et al. 2008). Impairments of burrowing behavior that facilitate predation are
well documented in invertebrates exposed to different classes of chemical contaminants
(Table 10.1).
Only few studies are available to make a judgment about the potential ecological conse-
quences of reduced predation efficiency and increased prey vulnerability on populations
and communities. Seven years after an oil spill, populations of the salt marsh crab Uca pug-
nax were still reduced as a consequence of the toxic effects of fuel oil on crab physiology
and behavior (Krebs and Burns 1977). These authors underline that reduction of the crab
population was ecologically significant since this species is important for the ecosystem
as a consequence of its role in energy flow through the system. As predators, crabs Cancer
magister can influence the species composition and diversity of soft-bottom communities:
when a prey species ( Protothaca staminea ) becomes more vulnerable as a consequence of
living in oiled sediment, predation by crabs is facilitated, thereby potentially reducing the
presence of the prey species among the benthic macrofauna (Pearson et al. 1981). Janssens
and Stoks (2012) have studied the vulnerability to predation in larvae of the damsel-
ly Enallagma cyathigerum exposed to a pesticide (endosulfan) or a herbicide  (Roundup).
Although both contaminants induced maladaptive changes in overall activity, only for
endosulfan this resulted in an increased mortality by predation as a consequence of dif-
ferent combined effects of these compounds on behavioral antipredator traits and escape
swimming.
In a comprehensive study with two fish and three crustacean species chronically
exposed in contaminated estuaries compared to conspecifics from a cleaner estuary, cas-
cading effects have been shown, linking infra-individual effects to effects at the com-
munity level (Table 10.2 after Weis et al. 2011). In most cases, behavioral disturbances
included a lower level of general activity, impaired prey capture, and increased vulner-
ability to predation. Altered thyroid status and altered levels of neurotransmitters may
be responsible for these impairments in fish. As a consequence of feeding impairments,
the diet of contaminated fish species and blue crabs was impoverished compared to their
noncontaminated conspecifics. This poor diet can account in part for the reduced size
observed in contaminated fish. In agreement with energy budget models (Maltby et al.
2001 and Chapter 12), population density of killifish Fundulus heteroclitus was reduced in
the impacted estuary. Surprisingly, in crustaceans, size was greater for individuals from
contaminated sites. In the cases of the grass shrimp Palaemonetes pugio and the blue crab
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