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Variations in the nonreactive P content of lake sediments as a consequence of changing redox conditions suggest that microorganisms may contribute to uptake and release of P. In this study, 31–50% of the nonreactive P was identified as polyphosphate (poly‐P) in NaOH extracts of sediments from eutrophic Lake Baldegg and oligo‐mesotrophic Lake Lucerne by means of 31 P NMR spectroscopy. Poly‐P was present in surface sediments but not in deeper sediment layers. In samples where poly‐P was detected, analysis under a scanning transmission electron microscope equipped with energy‐dispersive X‐ray spectroscopy indicated the presence of sediment bacteria containing P‐rich granules. Although poly‐P is stable in pure NaOH solution, it partially hydrolyzes during and after sediment extraction with NaOH. Cracking of poly‐P molecules to shorter fragments is, however, much slower if the sediment is pre‐extracted with EDTA and NaOH is replaced by a mixture of NaOH/EDTA to extract nonreactive P from sediments.
Hupfer et al. (Mon,) studied this question.