Marine Ecosystems under Toxic Pressure - Vulnerability of Coastal Ecosystems and Adaptation - page 24

in fresh and marine waters, involving both vertebrates and
invertebrates at once [CLE 99, CLE 09, DOD 95, HAM 95, KIF 96,
KRU 94, LEF 99, PRE 99, TAY 95, WEI 95, ZHO 99]. The increase
in the intensity of predation can lead to an increase in the rates of
trophic transfer from contaminants to contaminated prey to larger
predators;
- a reduced sensitivity to predation: the changes caused by the
contaminants on the behavior of prey that would decrease the
probability of encounters between prey and predators, thus reducing
the rates of predation, have received relatively little attention.
However, Taylor et al. [TAY 95] have found evidence of a decrease in
a cladoceran's capacity to swim in the presence of lindane. This
disruption has reduced its vulnerability to predation by the hydra
( Hydra oligactis ).
1.4.1.4. Interspecies competition within a same trophic behavior
One of the clearest cases in which contaminants can affect
interspecies competition can be found in the examples of differential
sensitivity in several species within a single trophic group. For
example, several studies have demonstrated that different groups of
zooplankton, which are in competition for phytoplankton, have
different sensitivities to insecticide (typically, cladocerans are more
sensitive than copepodes). Thus, when moderate concentrations of
insecticides are applied to communities containing cladocerans and
copepodes, a spectacular drop in the more sensitive cladocerans is
observed while the number of copepodes increases [HAV 93,
HAV 95, VAN 02, REL 05]. Several authors have also examined the
effects of insecticides on communities of macroinvertebrates
composed of several competing species. Thus, populations of
gastropods and oligochetes increase following exposure to a mixture
of lindane and chlorpyrifos to the detriment of crustaceans more
sensitive to these insecticides [CUP 02]. Differential sensitivity to
herbicides has also been documented among producers. In a green-
macrophyte algae system, the application of linuron leads to a drop in
the abundance of macrophytes, but an increase in the abundance of