1. Use of a novel laboratory stream system to study the ecological impact of PCB exposure in a periphytic biolayer

This research on PCB impact in stream sediments seeks to integrate ecologic al perspectives into the traditional physicochemical approach to hydrophobi c organic chemical (HOC) study. This paper presents the design and use of a novel laboratory stream system with a natural sediment substrate to study the response of a periphytic biolayer to low level PCB exposure over a 2-mo nth rime period. The results demonstrate that the laboratory stream system is a powerful tool to evaluate the biological impact and fate of PCBs. The results of biological monitoring demonstrated that the structure of the per iphytic community changed with exposure to PCBs. The periphytic community s hifted from one dominated solely by a diverse array of diatom taxa to one c o-dominated by fewer types of cyanobacteria (blue-green algae) and a single diatom taxon, This suggests that the structural changes in the community a re a good early bioindicator of contamination, whereas periphyton biomass ( chlorophyll a and biovolume), cell number or the presence/absence of partic ular species are not sensitive measures for assessing the ecological impact of pollutants. (C) 1999 Elsevier Science Ltd. All rights reserved.