Light and primary production shape bacterial activity and community composition in a mesocosm experiment

Metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon in the pelagial of aquatic environments. However, how changes in primary production affect bacterial activity and community composition remain largely unknown. For example, aerobic anoxygenic phototrophic bacteria are an important functional group involved in the utilization of phytoplankton derived dissolved organic carbon, but their coupling to phytoplankton primary production is still little understood. In the current study, primary production in a natural freshwater community was reduced either by lowering light intensity, or by inhibiting oxygenic photosynthesis to study the effects on the bacterial community composition and activity, in particular considering aerobic anoxygenic phototrophic bacteria.