Using extracellular enzymes to indicate impairments to ecosystem function in streams impacted by abandoned mine drainage in north central Pennsylvania

We used biofilm extracellular enzyme activities to investigate the effects of abandoned mine drainage (AMD) on ecosystem function for streams located in both the bituminous and anthracite coal regions of north central Pennsylvania.   Each regional sample contained one unimpacted reference stream, a remediated stream, and an AMD-impacted stream.  The AMD-impacted stream in the bituminous region had low pH, high concentrations of dissolved Al and Mn, and had very little metal deposition on the substrata.  The impacted stream in the anthracite region was relatively alkaline, had lower dissolved Al and Mn, but had considerable iron hydroxide deposition on the substrata.  Despite these differences, the activities of phosphatases compared to leucine-aminopeptidases were higher in both AMD-impacted streams compared to the reference streams, indicating extreme phosphorus limitation possibly due to phosphates adsorbing to heavy metals.  Iron hydroxide deposition in the anthracite stream appeared to more severely affect hydrolytic carbon-acquiring enzymes than the low pH of the bituminous stream.  The remediated streams generally had similar enzyme activities to the reference streams.  The overall results of the enzyme assays indicate that AMD has the potential to affect carbon, nitrogen and phosphorus cycling in streams and that remediation efforts might help to alleviate these impacts.