The potential control of benthic biofilm growth by macrophytes—A mesocosm approach

Abstract

Shallow lakes, ponds and wetlands are often colonized by high densities of photoautotrophic micro-organisms at their water–sediment interfaces. However, excessive growth of benthic biofilm may threaten ecosystem functioning. Under these conditions, ecological engineering solutions based on macrophyte introduction may be an efficient way to prevent biofilm development through biotic interactions (competition for light, nutrient and/or light, allelopathic effects). Therefore, the aim of this study was to evaluate the role of several macrophytes on biofilms developed at the water–sediment interface of sand filtration systems. Four species of allelopathic aquatic macrophytes common in European floodplains were selected: Vallisneria spiralis (L.), Berula erecta (Huds.) Coville, Ceratophyllum demersum (L.) and Chara globularis (L.). They were introduced in outdoor mesocosms filled with sandy sediments colonized by benthic biofilms. Monitoring was carried out for six weeks, with sampling of the 0–1cm layer in each mesocosm at the beginning and end of the experiment. Our results revealed a significant loss of biofilm algal biomass in treatments with V. spiralis and C. globularis. We also measured an inhibitory effect of C. globularis on the development of filamentous algae in the water column. These results demonstrate that the allelopathic activities of certain macrophytes could potentially prevent the excessive development of benthic biofilms in shallow lakes and wetlands.