Linking responses at different levels of biological organization: The effect on biomarkers and life cycle traits in the earthworm Eisenia andrei exposed to copper-spiked soils

Living organisms respond to chemicals at all the levels of biological organization, from molecules to ecosystems. In general, biochemical and physiological responses (molecules, cells, tissues) are triggered at low concentrations and after short exposure times, while ecological responses (life cycle traits, populations, communities, ecosystems) can be evidenced only at higher concentrations and after longer exposures. On the other hand, responses at the higher levels of organization are considered more relevant from an environmental point of view, as they often result in irreversible, severe damage to ecological systems. It is important to clarify the relationship between low-level and high-level responses to toxicants, particularly considering the increasing application of biomarkers as early warning systems to assess environmental pollution. In accordance with this view, effects of exposure to copper-spiked soils on life cycle endpoints were compared to effects on a battery of biomarkers in the earthworm Eisenia andrei. A natural clayey soil was spiked at seven copper concentrations, from 25 to 1600 mg/kg. Adult worms were exposed in laboratory to the spiked soils and to a control treatment (unspiked soil). Two sets of experimental container were prepared: the first to measure lisosomial stability, Ca2+ATP-ase activity, lipofuscin storage and metallotionein storage, after 10 d of exposure; the second to assess survival, growth and copper bioaccumulation after 28 d, and reproduction after 56 d of exposure. All the biological responses showed a clear concentration-effect relationship. EC50 was in the range 30–60 mg/kg of extractable copper for the physiological biomarkers (120–260 mg/kg total copper). EC50 for life cycle endpoints were noticeably higher, reproduction being the most sensitive.