Tuesday, June 5, 2007

Phosphorus limitation in the microbial community of an acid mine drainage-impacted stream in north central Pennsylvania, USA

Jennifer C. Biddinger and Steven T Rier. Department of Biological and Allied Health Sciences, Bloomsburg University, 400 East Second Street, Bloomsburg, PA 17815

Acid Mine Drainage (AMD) from abandoned mines is thought to impair vital stream ecosystem functions including, the ability of microbial communities to process inorganic nutrients and organic matter.  Previous work has indicated that extreme phosphorus limitation might be disrupting microbial communities in AMD-impacted systems.  We tested the hypothesis that microorganisms in AMD-impacted streams are phosphorus limited.  Nutrient diffusing substrata containing 2% agar were glued to clay tiles and deployed in either an AMD-impacted stream or an undisturbed control stream in Tioga County, Pennsylvania.  Each tile contained replicated (n=4) control (agar only), nitrogen (NaNO3), phosphorus (NaH2PO4), and nitrogen + phosphorus treatments.  After two weeks, each substratum was subsampled for chlorophyll a, phosphatase (APA) and leucine-amino peptidase (LAMP). Phosphorus appeared to be very limited within the AMD-impacted stream.  APA levels were significantly higher (p<0.05) than in the control, while LAMP was nearly undetectable.  Phosphorus additions within the AMD-impacted stream appeared to alleviate the phosphorus limitation by lowering levels of APA.  These results suggest that microbial processes within AMD-impacted streams may be affected by an imbalance between nitrogen and phosphorus which may result from heavy metals forming complexes with phosphates.