The relation between lysosomal biomarker and population responses in a field population of Microchaetus sp. (oligochaeta) exposed to the fungicide copper oxychloride

The ecological relevance of the neutral red retention assay as a biomarker in an indigenous earthworm population (Microchaetus sp.) exposed to the fungicide copper oxychloride was investigated. Changes in earthworm biomass and numbers were monitored and related to changes in neutral red retention times of coelomocytes as well as changes in copper concentrations in the soil and earthworm body tissues. Results indicated that Microchaetus sp. responded sensitively to the copper oxychloride by showing an initial decrease in biomass 2 months after spraying started. This was followed by a significant decrease in worm numbers after 3 months. The neutral red retention times of earthworm coelomocytes decreased significantly within the first month of treatment and correspond to a significant increase in soil copper concentrations, but not with an immediate increase in body burdens of copper. More than a year after spraying had stopped the worm biomass and numbers were still significantly lower in the treated plots compared with the control plots. Since the reduction in neutral red retention times could be attributed to the presence of copper oxychloride and preceded the decline in population density and biomass, we conclude that this biomarker has a useful role to play in environmental risk assessment and could provide a warning of impending ecological damage.