THE LAYERED AND HISTORICAL NATURE OF ECOLOGICAL-SYSTEMS AND THE RISK ASSESSMENT OF PESTICIDES

The community conditioning hypothesis is used as a framework in which to place the layers of effects during and after pesticide intoxication . Community conditioning states that information about the history of a system can be and is written at a variety of organismal and ecologic al levels. This historical component or etiology determines the future dynamics of a system. The storage of information concerning prior str essor events has been observed in a variety of compartments. Fish popu lations have been observed to have different genetic structures in pop ulations that have been exposed to toxicant stressors. Analysis of bio marker data from field experiments reveals a variety of patterns, some due to the location of the field plots. Treatment groups within a ser ies of microcosm experiments maintain their identities long after the degradation of the toxicant. The dynamics of the treatment groups in m ultivariate ecological space are characteristic of a particular treatm ent. Other microcosm systems differentially respond to invasion depend ing upon the order of the inoculation of the biotic components, even t hough at the time of the invasion the systems are indistinguishable, A major factor in the uncertainty of pesticide risk assessment will be the unknown etiology of the system of interest.