The faunal composition of topsoil samples from cores of 10 pasture soils irrigated with either tapwater or effluent from a biological sewage treatment plant, together with the fauna of the tapwater, the effluent, and the trickling filter were examined. The macrofauna was suppressed by the persistently wet conditions and no earthworms were recovered from any of the cores. The microfauna was well represented by microdrili nematodes, rotifers, gastrotrichs, tardigrades, and turbellarians. Protozoa were absent from the tapwater and the fauna of the topsoils irrigated with tapwater consisted of typical soil species. Differences among soils were comparable to those found in normal field samples, some soils having a richer fauna than others. The fauna of the effluent and the trickling filter were typical of those habitats, but few of these species persisted in the effluent-irrigated topsoils, which generally had a fauna similar to the topsoils irrigated with tapwater. There were more polysaprobic species and fewer mesosaprobic species in the effluent-irrigated topsoils, but generally differences among soils were greater than those between soil treatments.
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