Application of the Pollution-Induced Community Tolerance (PICT) method to algal communities:: its values as a diagnostic tool for ecotoxicological risk assessment in the aquatic environment

Methodologies based on physiological responses and biological community structure, such as the Pollution-Induced Community Tolerance (PICT) proposed by Blank et al 1988, are required to characterise ecosystem health. The PICT concept is based on the assumption that, when applied at a sufficient concentration for an adequate duration, a toxicant exerts a selection pressure towards a more tolerant community. Assessment of structural and physiological parameters, the latter obtained by exposing a community to increasing amounts ot toxicant, not only demonstrates the effects of exposure, but also allows comparison of the level of toxicant contamination between various sites from which algal communities have been collected. Classical approaches, microscopy and incorporation of C-14, have already been applied to microalgal cummunities in complex experimental systems and in the field. However, environmental conditions may be expected to influence community selection by the toxicant and may hamper the validation of PICT in situ. Development of new methodologies to characterise community structure and tolerance is fundamental for advancement of knowledge of ecological risk assessment.