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Free keywords:
bacterial carbon production; stream microbiology; sediment; Breitenbach; leucine incorporation
Abstract:
Bacterial carbon production (BCP) was measured in the upper 7 cm of the streambed sediments of a central German upland stream, the Breitenbach, monthly over one year by applying the leucine uptake technique. The two most common substrata were considered: sandy deposits and coarse deposits (gravel and pebble). Mean annual BCP was 7.8 µg (mL sediment)⁻¹ d⁻¹ in the sandy sediment and 3.6 µg (mL sediment)⁻¹ d⁻¹ in the coarse sediment (ranges: 4.8 to 11.3 µg mL⁻¹ d⁻¹ and 1.5 to 5.8 µg mL⁻¹ d⁻¹, respectively). BCP per streambed surface area varied from 0.34 to 0.79 g m⁻² d⁻¹ (average 0.55 g m⁻² d⁻¹) in the sandy deposits and from 0.10 to 0.41 g m⁻² d⁻¹ (average 0.25 g m⁻² d⁻¹) in the coarse deposits. Factors influencing the variability over time were mainly temperature and discharge. Effects of discharge were especially distinct after a spate in April, Total BCP for the streambed as a whole was 162 g m⁻² a⁻¹, which is in the medium range of the few studies on other streams and rivers. The coarse sediments contributed only 27 g m⁻² a⁻¹ to the total BCP because of its smaller and nearly constantly diminishing proportion during the investigation period. The amount of BCP is similar to total net primary production and much less than allochthonous organic matter inputs (>1100 g C m⁻² a⁻¹). Thus sufficient resources are available for maintaining BCP.
