Occurrence and ecological implications of pyrophosphate in estuaries

Loading of bioavailable phosphorus, traditionally measured as soluble react ive phosphorus (SRP), contributes to the eutrophication of aquatic ecosyste ms. However, polyphosphates. are also bioavailable but escape detection by the standard method used for measuring SRP. P-31 nuclear magnetic resonance spectrometric analysis of sediment extracts and enzymatic assay of surface waters reveal heretofore unreported presence of pyrophosphate (Ppi) in coa stal wetlands. We show that the accumulation of Ppi (the smallest chemical form of polyphosphate) in coastal wetlands is related to human impact and c an occur in quantities that exceed that of SRP. Vle further demonstrate tha t Ppi is readily utilized by microbes in coastal wetland sediments in the p resence of nitrogen and carbon and can serve as a reservoir of orthophospha te. Thus, Ppi accumulation in estuaries will subsidize the in situ biogeoch emical. phosphorus cycle. This has important ecological implications for tr ophic responses and estuarine productivity.