A critical review of procedures and approaches used for assessing
pollution-induced community tolerance (PICT) in biotic communities
Human and Ecological Risk Assessment, 8 (5):
1003-1034 (2002)Abstract
Pollution-induced community tolerance (PICT) is used for the detection
of minor effects of toxicants in biotic communities. Organisms survive
in toxic environments only if they are tolerant to the chemicals
present in their habitat. In the selection phase, toxicants hinder
the success of sensitive individuals and species and replace them
by more tolerant ones. The resulting increase in community tolerance
is quantified in the detection phase by short-term toxicity tests.
In this way PICT can establish causal linkages between contaminants
and effects. An increase in community tolerance compared to the baseline
tolerance at reference sites suggests that the community has been
adversely affected by toxicants. PICT has been used in aquatic and
terrestrial environments with communities of periphyton, phytoplankton,
bacteria, nematodes and insects. A variety of methods have been used
for quantification of community tolerance including photosynthesis,
sulfolipid synthesis, respiration, thymidine and leucine incorporation,
survival, and substrate utilisation patterns. PICT has been observed
for copper, zinc, nickel, mercury, cadmium, arsenate, monomethylarsonic
acid, diuron, tributyl tin, 4,5,6-trichloroguaiacol, irgarol 1051,
seanine 211, atrazine, and trinitrotoluene. It is necessary to validate
PICT, at least by showng that it is related to the preexposure concentration
of the toxicants and that it is coupled to a toxicant-induced succession
(TIS) in the community. Care must also be taken to ascertain that
PICT interpretation is not confounded by co-tolerance or bioavailability
differences. Co-tolerance patterns, which are indicative of the specificity
of PICT, have only been investigated for arsenate, diuron and a few
metals. For the further improvement of PICT methodology special attention
should be given to co-tolerance patterns and development of new integrating
short-term tests for quantification of tolerance. It is also important
to broaden the scope of organisms and toxicants used. Properly validated,
PICT is a powerful tool for detection of community effects and its
use in monitoring and site-specific risk assessment should be encouraged.