“Quantifying Natural Resource Damage: A Microbial Perspective”.
Wherever it occurs in the world, environmental destruction is the most visible outcome of surface mining. Surface mining destroys the physical and biological properties of soils and creates major landscape destruction such as deforestation, soil erosion, river silting, toxic metal pollution and acidification, major flora and fauna changes, and finally public health dangers such as heavy metal contaminated drinking water and food supply. Hence, restoration of mined lands is important and challenging. In this paper, we report a natural resource damage assessment analyzing the soil microbial community structure and function along a 100-year-old, heavy metal gradient in Western Montana, USA. We explored relationship between ecosystem level functioning and microbial community structure. We show that the ecosystem function of soil respiration declines 72% across the gradient due the combined factors of low pH and heavy metal concentration. The sensitivity of broad functional parameters (in situ soil respiration, microbial biomass) and microbial diversity [phospholipid fatty acid (PLFA) abundance and richness] were compared. Functional responses were linear with respect to contaminants while thresholds were detected in the community structural response to contamination along the gradient. For example, in situ soil respiration was negatively and linearly correlated to contamination concentration (R = −0.783, P < 0.01), but changes in microbial community structure only became evident where contaminant concentrations were greater than 28 times above background levels. Our results suggest that functional redundancy does not prevent depression of ecosystem function in the long-term when persistent heavy metals are present.