Redox-related release of phosphorus from sediments in large and shallow Lake Peipsi: Evidence from sediment studies and long-term monitoring data |
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| Affiliation: | 1. Freshwater Research, 3421 Hwy 117, Baysville, ON P0B 1A0, Canada;2. Ontario Ministry of Natural Resources and Forestry, 300 Water Street, Peterborough, ON K9J 3C7, Canada;3. Ontario Ministry of the Environment and Climate Change, Dorset Environmental Science Centre, Dorset, ON P0A 1E0, Canada;1. Biogeochemistry Group, Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Ontario, Canada;2. Ecological Modeling Group, Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C 1A4, Ontario, Canada;3. Department of Biology University of Waterloo, Waterloo N2L 3G1, Ontario, Canada;4. Lower Trent Region Conservation Authority, 714 Murray Street, Trenton K8V 5P4, Ontario, Canada;5. Kingston Regional Office, Ontario Ministry of the Environment and Climate Change, Kingston K7M 8S5, Ontario, Canada;1. Department of Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland;2. Department of Agricultural Sciences, University of Helsinki, P.O. Box 27, FI-00014 Helsinki, Finland;3. Centre for Limnology, Estonian University of Life Sciences, 61117 Rannu, Tartumaa, Estonia |
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| Abstract: | In large and shallow lakes, the role of the redox-related release of phosphorus (P) from sediments has remained in the shadow of sediment resuspension. In the current study, we concentrated on this knowledge gap regarding factors controlling lake water quality. We combined long-term monitoring data with the studies on sediment P mobility in August 2018 by measuring redox potential, pore water concentrations of soluble reactive phosphorus (SRP), dissolved iron (Fe), sediment P fractions, and by calculating diffusive P flux. Using lake water total P (TP) concentrations for 21 years (1997–2018), we quantified internal P load based on water column summer increase of TP (ILin situ). Significant positive correlations were found between the diffusive P flux and the Fe-bound P concentration in the sediment for conditions of well-oxidized sediment surfaces. The analysis of long-term data showed that P mobilized in sediments is likely to be released via sediment disturbances. Sediment resuspension is favoured by decreased water level during late summer-early autumn. Additionally, the release of P from anoxic sediment surfaces is also possible, as was indicated by significant positive correlations of ILin situ with the anoxic factor (a measure of extent of anoxia) and August water temperature. The potential P release from anoxic sediment surfaces contributed about 80% to ILin situ in the northern basin, and about 280% in the more productive southern basin. Hence, the redox-related P release seems to sustain the high productivity of these large and shallow lake basins and is supported by sediment resuspension as a transport mechanism. |
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| Keywords: | Redox potential Iron Sediment resuspension Anoxic factor Phosphorus fractions |
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