Ecosystem respiration increases with biofilm growth and bed forms: Flume measurements with resazurin

This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292169-8961/.In a set of streamside mesocosms, stream ecosystem respiration (ER) increased with biofilm\ud biomass and flow heterogeneity (turbulence) generated by impermeable bed forms, even though those\ud bed forms had no hyporheic exchange. Two streamside flumes with gravel beds (single layer of gravel) were\ud operated in parallel. The first flume had no bed forms, and the second flume had 10 cm high dune-shaped\ud bed forms with a wavelength of 1.0 m. Ecosystem respiration was measured via resazurin reduction to\ud resorufin in each flume at three different biomass stages during biofilm growth. Results support the\ud hypothesis that ER increases with flow heterogeneity generated by bed forms across all biofilm biomass\ud stages. For the same biofilm biomass, ER was up to 1.9 times larger for a flume with 10 cm high impermeable\ud bed forms than for a flume without the bed forms. Further, the amount of increase in ER associated with\ud impermeable bed forms was itself increased as biofilms grew. Regardless of bed forms, biofilms increased\ud transient storage by a factor of approximately 4