Sediment resuspension effects on dissolved organic carbon fluxes and microbial metabolic potentials in reservoirs
Sediment resuspension can affect water quality in lakes and reservoirs. We investigated the effect of sediment resuspension on benthic fluxes of dissolved organic carbon (DOC), metals (Fe, Mn), and nutrients (N, P) in three drinking water reservoirs using sediment core incubations. Measurement of Fe and Mn fluxes, and of microbial potentials to degrade organic substrates (Biolog EcoPlates™) were employed to understand mechanisms regulating DOC exchange after sediment resuspension. Single sediment resuspension events resulted in DOC fluxes [−104 (into sediment) to 46 (release) mmol m−2 event−1] equal to 9–17 days of diffusive fluxes, making them a relevant process. Shallow reservoir sites were more likely to immobilize DOC after resuspension than deep sites. Sediment resuspension under anoxia always led to increases of DOC and metals in the overlying water. Resuspension did not necessarily mobilize nitrate or phosphorus even under anoxia, while ammonium was released after resuspension. Sediment resuspension increased hypolimnetic microbial potentials to utilize organic substrates in both spring and summer. However microbial cells counts and biomass either remained constant or decreased in summer. Adsorption to Fe minerals seemed to play a role in DOC immobilization as evidenced by a decrease in DOC:Fe molar ratios after resuspension in Fe limited sites and constant ratios in Fe rich sites. The results demonstrate a potential for DOC immobilization mainly by Fe minerals and to some extent by benthic microbes. Therefore, sediment resuspension can be beneficial for water quality in low nutrient, iron rich systems.
KeywordsSediment resuspension DOC Biolog EcoPlates™ Microbial metabolic potential
This work was financially supported by the TALKO project (BMBF 02WT1290A). We thank Corinna Völkner for assisting with field sampling and cell counts, Juliane Schmidt for assistance in the laboratory, and the UFZ GEWANA for sample analysis. We acknowledge the stimulating reviews of Jürg Bloesch and an anonymous reviewer which significantly improved the manuscript.
- Björnsen Beratende Ingenieure GmbH (2012) Fortschreibung der Potentialstudie für das Bodesystem Bestandsaufnahme (Updating the potential study for Bode System inventory). In German. Talsperrenbetrieb Sachsen-Anhalt: Anstalt des öffentlichen Rechts, Blankenburg, KoblenzGoogle Scholar
- Eikebrokk B, Vogt RD, Liltved H (2004) NOM increase in Northern European source waters: discussion of possible causes and impacts on coagulation/contact filtration processes. Water Sci Technol 4:47–54Google Scholar
- Friese K, Schultze M, Boehrer B, Buettner O, Herzsprung P, Koschorreck M, Kuehn B, Roenicke H, Tittel J, Wendt-Potthoff K et al (2014) Ecological response of two hydro-morphological similar pre-dams to contrasting land-use in the Rappbode reservoir system (Germany). Int Rev Hydrobiol 99(5):335–349. doi: 10.1002/iroh.201301672 CrossRefGoogle Scholar
- Guizien K, Dupuy C, Ory P, Montanie H, Hartmann H, Chatelain M, Karpytchev M (2014) Microorganism dynamics during a rising tide: disentangling effects of resuspension and mixing with offshore waters above an intertidal mudflat. J Marine Syst 129:178–188. doi: 10.1016/j.jmarsys.2013.05.010 CrossRefGoogle Scholar
- Søndergaard M, Jeppesen E, Mortensen E, Dall E, Kristensen P, Sortkjær O (1990) Phytoplankton biomass reduction after planktivorous fish reduction in a shallow, eutrophic lake: a combined effect of reduced internal P-loading and increased zooplankton grazing. Hydrobiologia 200–201:229–240. doi: 10.1007/BF02530342 CrossRefGoogle Scholar
- Stumm W, Morgen JJ (1996) Aquatic chemistry: chemical equilibria and rates in natural waters. 3rd edn. Wiley, New YorkGoogle Scholar