title: Effects of drying on phosphorus uptake in re-flooded lake sediments.
abstract: Sediment drying associated with large water level fluctuations is an increasingly common feature of temporary streams and lakes worldwide. Drying-induced sediment aeration and re-flooding periodically alter redox conditions, and therefore stimulate redox-sensitive processes influencing phosphorus (P) binding forms. We experimentally tested the effects of drying on P binding forms, and the P sorption potential, by drying and re-flooding lake sediments in the laboratory. Wet and dried fine sediments were re-flooded in columns, and the overlying water was continuously re-stocked to a constant P concentration. We measured changes in P forms, P uptake rates, and the pore water dynamics in each column over 36 weeks. Drying decreased the fraction of stable P, stimulated the mineralization of organic P, and increased the proportion of labile and reductant-soluble forms. Drying of sediment furthermore reduced its P sorption affinity and capacity by up to 32% in batch equilibrium experiments, and led to a fourfold increase in sediment compaction which increased P uptake rates by a factor of 1.7 in sediment column experiments. Compaction due to drying also induced the development of a sharp gradient below which P was mobilized. These results indicate that in fine sediments, a single drying event can result in the transformation of P components into more labile forms which accumulate in the uppermost sediment layer, therefore raising the potential for a pulsed P release under reducing conditions.
authors.affiliation: Department of Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587, Berlin, Germany. Daniela.Dieter@uba.de.
authors.forename: Daniela
authors.initials: D
authors.lastname: Dieter
authors.affiliation: Department of Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587, Berlin, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Herzog
authors.affiliation: Department of Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587, Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hupfer
mesh_terms: D003890:Desiccation; D055868:Floods; D019015:Geologic Sediments / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D010758:Phosphorus / Q000032:analysis*
chemical_list: D010758:Phosphorus
keywords: Desiccation and re-flooding; Phosphorus fractionation; Phosphorus sorption; Sediment compaction; Sediment pore water; Water level fluctuation