Cu and Cd Effects on the Earthworm Lumbricus rubellus in the Laboratory: Multivariate Statistical Analysis of Relationships between Exposure, Biomarkers, and Ecologically Relevant Parameters

Abstract

This study sets out to examine the potential of a suite of novel molecular biomarkers as early warning indicators of environmental state and damage. Transcriptional responses of four genes, metallothionein 1 and 2, amine oxidase, and the lysosomal associated glycoprotein, were measured in the earthworm Lumbricus rubellus exposed to increasing concentrations of cadmium and copper in OECD soil. These responses were compared to metal body concentrations and lifecycle parameters: survival, cocoon production, and growth. Adverse physiological effects were observed at concentrations 1/3rd to 1/10th those of the artificial soil LC50. Multivariate statistics, principal component analysis (PCA), was used to investigate the correlations between the different variables. Three key components were derived explaining 77.6% of the variance, with component 1 contributing 32.4%, component 2 contributing 26.7%, and component 3 contributing 18.5%. These components were interpreted in terms of population health, pollutant exposure, and detoxification pathways, respectively. It is proposed that the use of such a suite of biomarkers could serve as indicators of the "health" of the soil environment and provide early warning signals of potential danger to the biota or as a means of monitoring soil remediation.