RESPONSES OF 2 EARTHWORM POPULATIONS WITH DIFFERENT EXPOSURE HISTORIES TO CHLOROPHENOL CONTAMINATION

Two populations of the earthworm Aporrectodea tuberculata (Eisen), one from a chlorophenol contaminated and another from an uncontaminated s ite in central Finland, were exposed to acute, toxic, and sublethal co ncentrations of pentachlorophenol (PCP). Exposure history seemed to ha ve only slight effect on the responses of the earthworms. Values of a lethal concentration of 50% in the humus-rich soil were very high, 1,8 70 mu g PCP per gram for the earthworms from the contaminated site and 1,520 mu g/g for the earthworms from the uncontaminated site. No diff erences in the accumulation of PCF from the soil into the earthworms b etween the two populations were found. Earthworms from both population s seemed to be able to avoid low concentrations of PCD. Earthworms fro m the contaminated site tended to product more cocoons in PCP-spiked t han in clean soil, whereas earthworms from the uncontaminated site pro duced more cocoons in clean soil. No other significant differences in the growth or reproduction between the populations were found. It seem s that in humus-rich soils chlorophenols have not acted as an importan t selection pressure, probably because of their strong sorption to soi l organic matter. However, the results showed that earthworms are able to reduce their exposure by avoidance behavior.