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RESEARCH PRODUCT

Responses of two earthworm populations with different exposure histories to chlorophenol contamination

subject

description

Two populations of the earthworm Aporrectodea tuberculata (Eisen), one from a chlorophenol contaminated and another from an uncontaminated site in central Finland, were exposed to acute, toxic, and sublethal concentrations of pentachlorophenol (PCP). Exposure history seemed to have only slight effect on the responses of the earthworms. Values of a lethal concentration of 50% in the humus-rich soil were very high, 1,870 μg PCP per gram for the earthworms from the contaminated site and 1,520 μg/g for the earthworms from the uncontaminated site. No differences in the accumulation of PCP from the soil into the earthworms between the two populations were found. Earthworms from both populations seemed to be able to avoid low concentrations of PCP. Earthworms from the contaminated site tended to produce more cocoons in PCP-spiked than in clean soil, whereas earthworms from the uncontaminated site produced more cocoons in clean soil. No other significant differences in the growth or reproduction between the populations were found. It seems that in humus-rich soils chlorophenols have not acted as an important selection pressure, probably because of their strong sorption to soil organic matter. However, the results showed that earthworms are able to reduce their exposure by avoidance behavior.