Effect of light regimes on the utilisation of an exogenous carbon source by freshwater biofilm communities

Abstract

Biofilms are a major source of ‘in stream’ primary production, exhibiting high population density, and being an important source of carbon for microbial heterotrophs. Changing patterns of land-use within freshwater catchment areas may greatly impact on stream biofilm microbial community structure, which in turn may influence the speed and extent with which full ecosystem recovery may occur. This study reports how freshwater biofilm communities respond to additions of acetate, used as a proxy for organic matter, the primary source of carbon within shaded forests and headwater streams. The use of [ 13C] acetate and subsequent isolation of 13C-labelled nucleic acids from the metabolically active fraction of the bacterial community enabled substrate assimilating organisms to be identified. In addition, biofilms were exposed to varied levels of incident light to assess the relative contribution of phototrophic and heterotrophic nutrition.