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constitutes a still unvalidated but probable hypothesis for explaining
certain collapses in marine species that are not otherwise understood:
such as stocks of farmed species not being replaced after the cessation
of farming, non-farmed species in decline and immune deficiencies in
cultivated species... Finally, the contamination of sea produce
consumed by mankind poses proven health problems and triggers
numerous halts in fishing activity (eels, shad, sardines, etc.).
Even more than for aquatic continental ecosystems, the object of
marine ecotoxicology is necessarily ecology under chronic toxic
stress. In effect, the contaminants involved are transported over tens of
thousands of kilometers, in a relatively little-fragmented environment.
They can survive over decades and infect the whole of the trophic
chain. These scales of time and biological organization immediately
pose questions at the level of ecology and indirect effects.
However, knowledge of them remains limited, since relatively few
experiments have been devised specifically to test it. Changes in
behavior, physiology, trophic interactions and/or competition between
species can produce changes in populations and the composition of the
community that intensify or mask the direct toxic effects. “Trophic
cascades” seem to be a shared type of indirect effect, but the setup of
most of the experiments does not permit the univocal distinction
between trophic interactions and interactions involving competition;
these two types of response are indirect effects, but result from very
different ecological processes.
More work is also necessary to understand the multiple stress
factors and know how, directly and indirectly, they influence the
structure and behavior of aquatic communities. Similarly,
complementary research should be carried out to develop ecosystem
models that describe and predict direct and indirect effects of
contaminants on a large variety of aquatic habitats. The aim of these
approaches should be to understand the ecological implications of
environmental stress factors, and, finally, to aid the development
of management strategies for preserving and restoring the integrity of
natural habitats. To understand the direct toxic effects of the
contaminants is, and will continue to be, an important part of this
process. However, communities and ecosystems are much more than
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