Effects of Copper and the Insecticide Cypermethrin on a Soil Ciliate (Protozoa: Ciliophora) Community

Ciliated protozoa play important ecological roles in soils, yet few studies have investigated the effect of soil pollution on them. We determined the effect of copper (Cu) and cypermethrin on a soil ciliate community under microcosm conditions. Soils were treated with Cu or cypermethrin and the abundance and species richness of ciliates determined 15 days later. Cu treatment increased soil ciliates abundance at the highest concentration (960 mg kg⁻¹), as did cypermethrin at a treatment of 160 mg kg⁻¹. No negative effect on ciliate abundance was found for either substance due to increased numbers of tolerant species, particularly Homalogastra setosa and Chilodonella uncinata in the case of Cu and Colpoda stenii and Colpoda inflata for cypermethrin treatments. However, several species were absent at high treatment levels. Notably, Halteria grandinella was not found in Cu treatments above 240 mg kg⁻¹, whilst Oxytricha setigera was not found in cypermethrin treatments above 160 mg kg⁻¹. For Homalogastra setosa, there was an initial positive response to cypermethrin, but abundance then decreased at a treatment of 320 mg kg⁻¹, and treatment at 640 mg kg⁻¹ eradicated the species from the microcosms. Accordingly, both substances affected the structure of the soil ciliate community at high concentrations.