Linking lysosomal biomarker and population responses in a field population of Aporrectodea caliginosa (Oligochaeta) exposed to the fungicide copper oxychloride

The effects of the fungicide copper oxychloride on a field population of the earthworm Aporrectodea caliginosa were investigated. Changes were monitored in earthworm numbers and biomass, copper concentrations in soil and earthworms, and neutral red retention times (NRRTs) of coelomocytes. The aim was to establish whether the cellular responses could be linked to changes at the population level. Results indicated that there was a significant (P<0.05) impact on worm density and biomass on the treated plots 6 months after spraying with the fungicide stopped. NRRTs of treated earthworms were significantly lower after one spraying when earthworms had elevated concentrations of copper in their body tissues. Six months after spraying stopped, copper levels in both soil and earthworm tissues declined significantly, but the earthworm numbers and biomass were still significantly lower in the treated plots. This indicated that the effects of the copper oxychloride exposure manifested at a much later stage at the population level, than on NRRT. We conclude that the decrease in NRRTs, which preceded the decrease in both earthworm biomass and numbers, may have predictive value as a biomarker of impending population changes.