FIG. 1.

Chemical depth profile and nitrate, sulfate, Fe(II), and total Fe concentrations (A) and most probable number enumeration of nitrate-dependent Fe(II)-oxidizing microbial community at given depths (B) for Campus Lake sediment. (A) ▪, Fe(II); □, FeT; ▴, SO₄²⁻; bars, NO₃⁻. The absence of bars denotes nitrate concentrations below the detection limit. For panel B, error bars associated with MPN enumeration are 95% confidence limits calculated by the Most Probable Number Calculator version 4.05 (Albert J. Klee, Risk Reduction Engineering Laboratory, United States Environmental Protection Agency, Cincinnati, Ohio, 1996; freeware available at http://www.epa.gov/nerlcwww/other.htm).