Abstract
We studied the potential release of phosphorus from the surface sediments of two shallow eutrophic lakes, plankton-dominated Lake Kaiavere and calcareous macrophyte-dominated Lake Prossa, in relation to phosphorus forms and anoxic-oxic conditions. The distribution of phosphorus forms was determined before and after six-week-long incubation of the sediments in oxic and anoxic (H2S enriched) conditions. The phosphorus fractionation scheme of Psenner et al. (1988) was basically followed. Summarising the release from all considered fractions, the L. Kaiavere sediment lost two times more phosphorus in anoxic than in oxic conditions while no significant difference between these oxygen conditions was found in the L. Prossa sediment. NH4Cl-RP and NaOH-RP showed similar release patterns in both sediments. In NaOH-NRP (the dominant fraction in both sediments), BD-RP and HCl-RP differences between lakes occurred. About half of the HCl-RP pool in L. Prossa sediment was released during the incubation whereas the phosphorus content in this fraction remained comparatively stable in L. Kaiavere sediments. Calcium-bound phosphorus compounds measured in this fraction seem to have a variable potential mobility. The results of this study indicate that the potential phosphorus release from a single sediment phosphorus fraction may differ between lakes despite similar oxygen conditions.
Published Version
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