Premium
Interaction modification among decomposers impairs ecosystem processes in lead‐polluted soil
Author(s) -
Salminen Janne,
Korkama Tiina,
Stroömmer Rauni
Publication year - 2002
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620211107
Subject(s) - decomposer , trophic level , food web , ecology , microcosm , trophic cascade , soil food web , humus , biology , ecosystem , environmental science , soil biology , mesocosm , pollution , environmental chemistry , soil water , chemistry
Environmental pollution by toxicants is generally believed to lead both to direct toxic effects and indirect effects via altered species interactions in a stressed community. We examined how contamination of a coniferous forest soil floor by lead (from an abandoned shooting range area) may alter trophic interactions and decomposition processes. We constructed laboratory microcosms containing microbial‐based food webs with various trophic structures: microbes alone; microbes with microbivorous‐ detritivorous enchytraeid worms (Cognettia sphagnetorum, a potential keystone species of boreal forest soil); and microbes, worms, and predatory mites (Lysigamasus spp.) together. The direct toxic effect of lead and the effectiveness of the predators in preying upon the worms were studied in separate experiments. Polluted humic soil (acid‐extractable lead concentration was 2,720 ± 349 mg/kg of dry soil [mean 6 standard error]) was toxic to enchytraeids, and predators effectively reduced worm populations. Positive density‐dependent effects of worms on microbes and a trophic cascade from predatory mites to microbes, observed in the unpolluted humus, were not observed in the polluted humus, indicating pollution‐induced interaction modification among organisms. Concomitantly, lead pollution altered the process of nutrient mineralization in the humic soil. However, causality and relative importance of direct toxicity and indirect effects of lead on the dynamics of the decomposer food web could not be pointed out. Examination of our results indicates that traditional food web models are incapable of predicting mechanisms that alter dynamics of pollutionstressed belowground food webs.