Impact of storm‐flow on electron transport system activity in river biofilms

Abstract

SUMMARY 1. The effect of storm‐flow on light‐ and dark‐grown biofilms from a North Wales river was monitored using electron transport system (ETS) activity and epifluorescence cell counts. 2. Artificial substrata were colonized in the river, exposed to ambient‐flow (60 cms −1 ) or storm‐flow (235 cms −1 with suspended sediment addition) for 12h in a laboratory flow tank, and returned to the river to monitor the recovery period. 3. Total cell densities decreased in both the light‐ and dark‐grown biofilms as a result of storm‐flow. In addition, storm‐flow ETS activity per cell increased significantly in the light‐grown samples (2.7 times) but did not increase significantly in the dark‐grown samples (1.6 times). 5. Within 48 h, storm‐flow total cell densities and ETS activity levels had returned to ambient‐flow levels in both light‐ and dark‐grown biofilms. 6. Within each light regime, despite their different histories, both ambient and storm‐flow samples responded the same to daily changes in the river environment, including a second disruption by natural causes, for the remainder of the 24‐day experiment.