SOIL MICROCOSM FOR TESTING THE EFFECTS OF CHEMICAL-POLLUTANTS ON SOILFAUNA COMMUNITIES AND TROPHIC STRUCTURE

A microcosm technique is presented that uses community and trophic-lev el analysis of soil nematodes and microarthropods to determine the eff ects of chemicals on soil systems. Forest soil was treated with either copper (0, 100, 200, 400, and 600 mug g-1), p-nitrophenol (0, 20, 40, 80, and 160 mug g-1), or trinitrotoluene (0, 25, 50, 100, and 200 mug g-1). Nematodes were sorted into bacterivore, fungivore, herbivore, a nd omnivore-predator trophic groups, and a hatchling category. Microar thropods were sorted to the acarine suborders Prostigmata, Mesostigmat a, and Oribatida; the insectan order Collembola; and a miscellaneous g roup. Omnivore-predator nematodes and meso-stigmatid and oribatid mite s were the groups most sensitive to copper and were significantly redu ced at levels as low as 100 mug g-1 copper. Total nematode and microar thropod numbers declined above 200 mug g-1 copper. Trophic structure a nalysis suggested that high sensitivity of nematode predators to inter mediate levels of copper reduced predation on herbivore nematodes and resulted in greater numbers of nematodes compared to controls. p-Nitro phenol was very toxic to the nematode community, and all trophic group s were significantly reduced above 20 mug g-1. However, there was no e ffect of p-nitrophenol on microarthropods. Trinitrotoluene had no sign ificant negative effect on total abundance of either group of soil fau na, but oribatids were significantly reduced at 200 mug g-1. Our resul ts demonstrated that soil nematodes and microarthropods were sensitive indicators of environmental contaminants and that trophic-structure a nd community analysis has the potential to detect more subtle indirect effects of chemicals on soil food-web structure. We conclude that mic rocosms with field communities of soil microfauna offer high resolutio n of the ecotoxicological effects of chemicals in complex soil systems .