Extent of copper tolerance and consequences for functional stability of the ammonia-oxidizing community in long-term copper-contaminated soils

Authors

  • Jelle Mertens,

    Corresponding author
    1. K.U.Leuven, Faculty of Bioscience Engineering, Department of Earth and Environmental Sciences, Division Soil and Water Management, Kasteelpark Arenberg, 20 Box 2459, 3001 Heverlee, Belgium
    • K.U.Leuven, Faculty of Bioscience Engineering, Department of Earth and Environmental Sciences, Division Soil and Water Management, Kasteelpark Arenberg, 20 Box 2459, 3001 Heverlee, Belgium.
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  • Steven A. Wakelin,

    1. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, Environmental Biogeochemistry, PMB2, Glen Osmond, South Australia 5064, Australia
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  • Kris Broos,

    1. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, Environmental Biogeochemistry, PMB2, Glen Osmond, South Australia 5064, Australia
    2. VITO—Flemish Institute for Technological Research, Boeretang 200, 2400 Mol, Belgium
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  • Mike J. McLaughlin,

    1. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, Environmental Biogeochemistry, PMB2, Glen Osmond, South Australia 5064, Australia
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  • Erik Smolders

    1. K.U.Leuven, Faculty of Bioscience Engineering, Department of Earth and Environmental Sciences, Division Soil and Water Management, Kasteelpark Arenberg, 20 Box 2459, 3001 Heverlee, Belgium
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Abstract

Adaptation of soil microbial communities to elevated copper (Cu) concentrations has been well documented. However, effects of long-term Cu exposure on adaptation responses associated with functional stability and structural composition within the nitrifying community are still unknown. Soils were sampled in three field sites (Denmark, Thailand, and Australia) where Cu gradients had been established from 3 to 80 years prior to sampling. In each field site, the potential nitrification rate (PNR) decreased by over 50% with increasing soil Cu, irrespective of a 20 to >200-fold increase in Cu tolerance (at the highest soil Cu) among the nitrifying communities. This increased tolerance was associated with decreasing numbers (15–120-fold) of ammonia-oxidizing bacteria (AOB), except in the oldest contaminated field site, decreasing numbers of ammonia-oxidizing archaea (AOA; 10–130-fold) and differences in the operational taxonomic unit (OTU) composition of the AOB and, to a lesser extent, AOA communities. The sensitivity of nitrifying communities, previously under long-term Cu exposure, to additional stresses was assessed. Nitrification in soils from the three field sites was measured following acidification, pesticide addition, freeze–thaw cycles, and dry–rewetting cycles. Functional stability of the nitrification process was assessed immediately after stress application (resistance) and after an additional three weeks of incubation (resilience). No indications were found that long-term Cu exposure affected the sensitivity to the selected stressors, suggesting that resistance and resilience were unaffected. It was concluded that the nitrifying community changed structurally in all long-term Cu-exposed field sites and that these changes were associated with increased Cu tolerance but not with a loss of functional stability. Environ. Toxicol. Chem. 2010;29:27–37. © 2009 SETAC

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