INTRODUCTION
While individuals are the traditional subjects of toxicology,
ecotoxicology aims to identify toxic effects on populations
and communities of organisms. Modern societal requirements
of ecotoxicology as a science include the provision of a picture
as complete as possible of the potential effects of polluting
agents at the individual, community, and ecosystem levels,
accounting for both direct and indirect effects. At present, these
requirements can be met only to a limited extent. Individuals
have a modal life span, but populations and communities do
not, although they can eventually become extinct, as shown
by examples in the fossil record. Individuals occupy a discrete
space in nature, while populations and communities occur
within highly variable bounds. In ecotoxicology, we need to
deal with the problem of finding acceptable temporal and spatial
scales of analysis for the occurrence of populations and
communities that would not compromise their conservation
and/or health.