Measurement of bacterial production in stream-bed sediments via leucine incorporation

Abstract: The leucine incorporation technique was evaluated and optimised for measuring bacterial production in stream-bed sediments. The original procedure was modified in order to obtain reliable production estimates in this habitat. This included the use of higher leucine concentrations (50 μmol l⁻¹) for obtaining substrate saturation, and an enhanced protein extraction procedure after sample fixation. The leucine method was combined with a perfused core technique. Water containing ¹⁴C-labelled leucine was perfused up through sediment cores, enabling the measurement of bacterial production in an experimental situation resembling natural conditions in the stream bed. Bacterial production in the Breitenbach, a small upland stream in Central Germany, showed a high degree of spatial variability in the sandy stream bed. It was related closely to sediment organic matter content, whereas varying perfusion rates had less influence. Annual bacterial production was estimated at about 200 g C m⁻², demonstrating the potential for bacteria to act as a food resource for benthic fauna in this stream.