Phosphorus Entrainment Due to Resuspension in a Lowland River, Spree, NE Germany – A Laboratory Microcosm Study |
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Authors: | Andreas Kleeberg Michael Hupfer Giselher Gust |
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Affiliation: | 1. Leibniz Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587, Berlin, Germany 2. Ocean Engineering 1, Hamburg University of Science and Technology, Schwarzenbergstr. 95, 21073, Hamburg, Germany
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Abstract: | Resuspension of benthic phosphorus (P) often constitutes a high percentage of the annual P flux in lowland rivers. To study P entrainment at controlled shear velocity (u*) sediment from lowland River Spree of slower flowing (0.1–0.3 m s?1) stretch Kossenblatt (KOB) and of faster flowing (0.5–0.7 m s?1) stretch Freienbrink (FRB) was incubated in a microcosm at incrementally enhanced u* (0.34–1.9 cm s?1). Particle and P entrainment rates as well as the number of particle-associated bacteria of fine-grained mud-like KOB sediment were much higher (16.7 g m?2 h?1, 104.9 mg P m?2 h?1, 15.47 106 cells ml?1) than those (4.3 g m?2 h?1, 2.1 mg P m?2 h?1, 3.06 106 cells ml?1) of coarser sandy FRB sediment. The microcosm used so far in marine research is suited to compare riverine resuspension suggesting the lower u* the more particles are deposited and the more P can be retained (KOB ? FRB). Conversely, correspondingly more and easier particulate P and bacteria can again be remobilised (KOB ? FRB) if u* increases. The general relationship found for u* and the entrainment of particulate P and bacteria as well as their decelerated and selective deposition where bacteria may stay longer in the water implies a temporarily enhanced P bioavailability, turnover and subsequent P transformations. |
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