DROUGHT TOLERANCE IN FOLSOMIA-CANDIDA WILLEM (COLLEMHOLA) AFTER EXPOSURE TO SUBLETHAL CONCENTRATIONS OF 3 SOIL-POLLUTING CHEMICALS

Drought tolerance (survival) was studied in the collembolan Folsomia c andida Willem influenced by sublethal concentrations of nonylphenol (4 0 mg/kg dry soil), linear alkylbenzene sulphonate (LAS) (500 mg/kg) an d copper (300 mg/kg). The collembolans were initially exposed to the t oxic compounds via soil and thereafter exposed to different degrees of drought stress in the laboratory. F. candida survived long-term expos ure (7 days) in air with a relative humidity (RH) of 98.5 % at 20 degr ees C. At the lowest humidity (96.8 % RH) survival in control animals was low, between 0 and 30 %. Animals previously exposed to nonylphenol and copper had decreased drought survival compared to control animals , whereas the chemicals alone had no lethal effect. The effects of LAS were not statistically significant although there was a tendency to l owered drought tolerance in exposed animals. The possible physiologica l mechanisms involved in drought tolerance, and how these may be affec ted by chemicals, are discussed. The ecological significance of these observations is that severe drought periods may significantly increase the risk of extinction of F. candida (or other species) in a polluted habitat compared to an unpolluted habitat.