Soil microcosm for testing the effects of chemical pollutants on soil fauna communities and trophic structure

Abstract

AbstractA microcosm technique is presented that uses community and trophic‐level analysis of soil nematodes and microarthropods to determine the effects of chemicals on soil systems. Forest soil was treated with either copper (0, 100, 200, 400, and 600 m̈g g−1), p‐nitrophenol (0, 20, 40, 80, and 160 m̈g g−1), or trinitrotoluene (0, 25, 50, 100, and 200 m̈g g−1). Nematodes were sorted into bacterivore, fungivore, herbivore, and omnivore‐predator trophic groups, and a hatchling category. Microarthropods were sorted to the acarine suborders Prostigmata, Mesostigmata, and Oribatida; the insectan order Collembola; and a miscellaneous group. Omnivore‐predator nematodes and mesostigmatid and oribatid mites were the groups most sensitive to copper and were significantly reduced at levels as low as 100 m̈g g−1 copper. Total nematode and microarthropod numbers declined above 200 m̈g g−1 copper. Trophic structure analysis suggested that high sensitivity of nematode predators to intermediate levels of copper reduced predation on herbivore nematodes and resulted in greater numbers of nematodes compared to controls. p‐Nitrophenol was very toxic to the nematode community, and all trophic groups were significantly reduced above 20 m̈g g−1. However, there was no effect of p‐nitrophenol on microarthropods. Trinitrotoluene had no significant negative effect on total abundance of either group of soil fauna, but oribatids were significantly reduced at 200 m̈g g−1. Our results demonstrated that soil nematodes and microarthropods were sensitive indicators of environmental contaminants and that trophic‐structure and community analysis has the potential to detect more subtle indirect effects of chemicals on soil food‐web structure. We conclude that microcosms with field communities of soil microfauna offer high resolution of the ecotoxicological effects of chemicals in complex soil systems.