FIG. 3.
(a and b) Microprofiles of NO3−, NO2−, redox potential (RP), and pH in NA and control biofilms grown in situ on carbon steel coupons for 4 months. (c and d) The situation 4 days after biofilm exchange to opposite NO3− conditions, designated NA(−) and control(+) biofilms. H2S, H2, and N2O were not detected in any biofilm. Zero depth indicates the biofilm-water boundary; dashed lines represent the estimated metal coupon surface position. Averages and standard deviations were calculated from three profiles measured across the biofilm.