Table 3.

Bacterial community tolerance of metals in Luddington

TreatmentCommunity tolerance (IC50) ofa:
CuZnNiCd
Uncontaminated sludge−6.16−4.79−4.21−4.70
No sludge−5.83* (0.34)−4.61 (0.18)−4.21 (0.00)−4.46 (0.24)
Low Cu−5.48* (0.68)NDNDND
High Cu−5.18* (0.98)−4.10* (0.69)−3.91 (0.30)−4.10* (0.60)
Low ZnND−4.32* (0.37)NDND
High Zn−5.55* (0.61)−3.93* (0.86)−3.77 (0.55)−4.01* (0.69)
Low NiNDND−3.82 (0.39)ND
High Ni−5.90 (0.26)−4.15* (0.64)−3.11* (1.10)−4.35 (0.35)
Mean SE0.110.140.280.15
  • a IC50s are expressed as log metal concentrations. Values in parentheses denote ΔIC50. Asterisks indicate significant difference from the uncontaminated-sludge treatment (n = 4,P < 0.05, mean SE from ANOVA). ND, not determined.