title: Internal phosphorus loading across a cascade of three eutrophic basins: A synthesis of short- and long-term studies.
abstract: Ascertaining the phosphorus (P) release processes in polymictic lakes is one of the methodologically most complex questions in limnology. In the current study, we combined short- and long-term investigations to elucidate the role of sediments in the P budget in a chain of eutrophic lake basins. We quantified the internal loading of P in three basins of Lake Peipsi (Estonia/Russia) for two periods characterized by different external P loadings using radiometrically dated sediment cores (long-term studies). The relationships between different water quality variables and the internal P loading, and the external P loading were studied. Our short-term studies aimed at elucidating the possible mechanisms behind variations in internal P loading included examination of the surficial sediments, i.e., seasonal measurements of redox potential, sediment pore water P concentrations and diffusive fluxes. Our results provided evidence for a potentially high importance of internal P loading in regulating water quality. The sediment core analyses revealed an increase in the internal P loading during the period of lower external P loading coinciding with the general deterioration in the lake water quality (i.e, higher concentrations of soluble reactive phosphorus, total phosphorus and biomass of cyanobacteria). Increase in wave action between the two studied periods appeared to cause more frequent sediment resuspension, and thus be the most likely reason for the variations in internal P loading. Our short-term measurements indicated that resuspension events can be followed by a considerable increase in the diffusive fluxes.
authors: Department of Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland; Centre for Limnology, Estonian University of Life Sciences, 61117 Rannu, Tartumaa, Estonia. Electronic address: olga.tammeorg@helsinki.fi.
authors: Olga
authors: O
authors: Tammeorg
authors: Department of Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland. Electronic address: horppila@mappi.helsinki.fi.
authors: Jukka
authors: J
authors: Horppila
authors: Department of Agricultural Sciences, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland. Electronic address: priit.tammeorg@helsinki.fi.
authors: Priit
authors: P
authors: Tammeorg
authors: Centre for Limnology, Estonian University of Life Sciences, 61117 Rannu, Tartumaa, Estonia. Electronic address: marina.haldna@emu.ee.
authors: Marina
authors: M
authors: Haldna
authors: Department of Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland. Electronic address: juha.niemisto@helsinki.fi.
authors: Juha
authors: J
authors: Niemistö
mesh_terms: D018533:Biomass; D000458:Cyanobacteria / Q000378:metabolism*; D004784:Environmental Monitoring; D004957:Estonia; D005068:Eutrophication; D019015:Geologic Sediments / Q000032:analysis*; D060106:Lakes / Q000737:chemistry* / Q000382:microbiology; D010758:Phosphorus / Q000032:analysis*; D017553:Phosphorus Compounds / Q000032:analysis; D012426:Russia; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D017553:Phosphorus Compounds; D014874:Water Pollutants, Chemical; D010758:Phosphorus
keywords: Diffusion; Internal phosphorus loading; Phosphorus retention; Redox potential, resuspension