ABSTRACT
The defi nition of biomarkers has been enunciated in many different forms as a refl ection of their intense use in the environmental sciences over the past decades (NRC 1987; Schlenk 1999; Depledge et al. 1992; Adams 1987). In essence, a biomarker is any indicator of a stress agent that is somehow affecting an organism’s ability to grow, reproduce, survive and adapt (or in other words, to live) in a given environment. In fact, the term biomarker is most accurately used to refer to an indicator at a sub-individual or, at most, an individual level of organization; this indicator may be alterations in molecular and biochemical processes, cellular structures and functions, tissue organization or mass and length ratios of individual organs or the whole body.
