Variability in acetylcholinesterase and glutathione S-transferase activities in Chironomus riparius Meigen deployed in situ at uncontaminated field sites

An in situ system was used to expose fourth instar Chironomus riparius Meig en larvae for 48-h at 13 uncontaminated river sites across southeast Englan d. Acetylcholinesterase (AChE) and glutathione S-transferase (GST) activiti es were measured in individual larvae recovered from these sites. Activitie s of both biomarkers varied almost twofold across the sites, with statistic ally significant differences detectable between sites. There were no clear relationships between biomarker activities and physical or chemical charact eristics measured at each site. This study shows that biomarker measurement s can be used successfully in conjunction with an in situ system. However, the results of statistically significant biomarker results must be treated with caution because natural variability in responses can occur even in the absence of toxicant exposure.