Integrating effects of contaminants across levels of biological organization: an overview

Effects of contaminants may occur at all levels oforganization, from molecular to ecosystem-levelresponses. While biochemical and physiologicalalterations in organisms may occur rapidly and areoften stressor-specific, the ecological relevance ofthese suborganismal indicators is uncertain.Alterations in populations and communities havegreater ecological relevance, but a firm mechanisticunderstanding of these responses is often lacking.Developing mechanistic linkages across levels ofbiological organization would greatly improve ourunderstanding of how organisms are affected bycontaminants in nature. The papers in this seriespresent several innovative approaches for integratingeffects of contaminants across levels of biologicalorganization. Authors were asked to describe theecological consequences of responses at lower levelsof organization (biochemical, physiological,individual) and to speculate on the underlyingmechanisms associated with population and communityalterations. The most consistent finding of the fivepapers in this series is that there is no singlespatiotemporal scale or level of biologicalorganization at which ecotoxicological investigationsshould be conducted.     

On Choice of Subjects and Replicates in Estimating Among and Within Subject Variation

We consider the problem of choosing the number of replicates and number of subjects in a components of variance problem which optimizes various criteria. The case study here involves patients suffering from systemic sclerosis (Scleroderma), a form of rheumatic disease that is potentially disabling. Under the physical constraints imposed on the study, we find that using 2 or 3 replicates with as many patients as possible is the optimal strategy for several criteria.