Advances in Using Oxygen Isotope Ratios of Phosphate to Understand Phosphorus Cycling in the Environment

Jaisi, Deb P.; Blake, Ruth E.

doi:10.1016/b978-0-12-800137-0.00001-7

Cited by 52 publications

(52 citation statements)

References 172 publications

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“…As the exchange of oxygen between soil phosphate and water at 25°C must involve enzymatic reactions (Kolodny et al, 1983;Tudge, 1960), we conclude that the movement toward the steady-state value was mediated by biological processes. Previous studies (Angert et al, 2012;Jaisi & Blake, 2014;Tamburini et al, 2012) have shown that the main reaction that drives the soil δ 18 O P is equilibration with the soil water, probably mediated by intercellular pyrophosphatase activity. While extracellular pyrophosphatase activity that mineralize organic P compounds have diverse isotopic effects, which are enzyme and substrate dependent (Liang & Blake, 2009;von Sperber et al, 2015), their effect on soil δ 18 O P was found to be small, since equilibration quickly erase their signature .…”

Section: Discussionmentioning

confidence: 98%

Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes

et al. 2018

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Soil phosphate oxygen isotope analysis (δ18OP) emerges as an effective method to trace the cycling of phosphorus (P) in soils. This study uses δ18OP measurements to learn how the nutrient status (P and N) affects the biological turnover rates of P in the soil of a Mediterranean holm oak Savanna. Such ecosystems cover >3 × 106 ha at the Iberian Peninsula. The analysis was part of a large‐scale nutrient manipulation experiment, where N and P were added. We followed the changes in δ18O values of soil bioavailable P during incubation of soils with a pulse of P and in addition measured the δ18OP in soil sampled at the site. In the incubations, the δ18OP values changed from the original value of the added P and approached a steady state of 16.3‰, which is 3.8‰ higher than the isotopic equilibrium with water. The steady state was higher with 18O‐enriched incubation media water. The change in δ18OP values was more pronounced under trees, indicating a faster microbial P turnover rate. Incubation of soils fertilized with either P or N showed faster P turnover rate than control, implying N and P colimitation. Soil samples from P‐fertilized plots displayed higher δ18OP than the fertilizer, rather than the expected decrease toward steady‐state values, found at the control and N plots. The microbial P turnover rates during incubations were slower than the rates reported for lowland tropical forest with lower bioavailable P concentrations but resemble ecosystems with similar concentrations.

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Section: Discussionmentioning

confidence: 98%

Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes

et al. 2018

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“…Phosphate (PO 4 ) oxygen isotope ratios (δ 18 O P ) have been applied as a tool to investigate P cycling (P sources and biological transformations) in aquatic environments [ Colman et al ., ; Elsbury et al ., ; Goldhammer et al ., ; Gooddy et al ., ; Jaisi and Blake , ; McLaughlin et al ., , ; Paytan and McLaughlin , ; Paytan et al ., ; Young et al ., ]. The strong bonding between atoms of oxygen and phosphorus (P–O bond) in phosphate prevent oxygen exchange under most environmentally relevant conditions (Earth surface pressure, temperature (<80°C) and pH) [ Jaisi and Blake , ; Lécuyer et al ., ]. Therefore, a negligible isotopic effect is expected for abiotic processes such as sorption, desorption, precipitation, and transport [ Jaisi et al ., , ; Liang and Blake , ], which allows tracking of P sources [ Elsbury et al ., ; Gooddy et al ., ; McLaughlin et al ., ; Young et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Phosphorus availability and turnover in the Chesapeake Bay: Insights from nutrient stoichiometry and phosphate oxygen isotope ratios

Bai

Bear

et al. 2017

JGR Biogeosciences

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Understanding phosphorus (P) availability and its control on eutrophication in the Chesapeake Bay is complicated by variable sources and biogeochemical reactions transforming P forms. We investigated seasonal and spatial variability in P limitation and biological utilization in the Bay using nutrient stoichiometry (of both dissolved and particulate forms), phosphate oxygen isotope ratios, and alkaline phosphatase activity at three sites along the salinity gradient. We demonstrate that particulate nutrient ratios can be used as indicators of nutrient limitation in the Bay and suggest strong seasonal and spatial variability in P availability: the surface water is P limiting in spring, but this condition is alleviated in summer and in the deeper waters. Variability in P limitation is well reflected in the trends of phosphate oxygen isotope composition (δ18OP), with values approaching isotopic equilibrium under P limiting conditions, suggesting rapid biological P turnover. Furthermore δ18OP values suggest multiple phosphate sources including remobilization of terrestrial inorganic P phases and remineralization of organic P and P from both sources is sufficiently cycled by microorganisms, suggested by the extensive equilibrium oxygen isotope exchange. Our results further suggest high P utilization in the deeper euphotic zone where nutrients are abundant, raising caution on studying nutrient availability and limitation only in the surface water.

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“…However, it would seem that the combination of organic material, faecal anions, and the anions within the solution itself significantly reduced the recovery of PO 4 on the resins in a way that did not occur in just the Ringer's solution alone. This interference raises questions about the validity of the δ 18 O PO4 values of PO 4 recovered in this solution due to potential unknown fractionations that might occur as a result of preferential adsorption/desorption of the lighter/heavier isotopologues . The microbiological analysis showed that cell lysis and rupture did not occur in either extraction (Table ).…”

Section: Discussionmentioning

confidence: 97%

“…This interference raises questions about the validity of the δ 18 O PO4 values of PO 4 recovered in this solution due to potential unknown fractionations that might occur as a result of preferential adsorption/desorption of the lighter/heavier isotopologues. 36 The microbiological analysis showed that cell lysis and rupture did not occur in either extraction (Table 3). Therefore, the results derived from the Ringer's solution extraction are not considered further in this discussion, as it apparent that the method for distinguishing microbial PO 4 from inorganic PO 4 (as defined earlier) requires further development.…”

Section: Resin-extractable Pomentioning

confidence: 99%

The stable oxygen isotope ratio of resin extractable phosphate derived from fresh cattle faeces

Granger

Yang

Pfahler

et al. 2018

Rapid Comm Mass Spectrometry

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RationalePhosphorus losses from agriculture pose an environmental threat to watercourses. A new approach using the stable oxygen isotope ratio of oxygen in phosphate (δ18OPO4 value) may help elucidate some phosphorus sources and cycling. Accurately determined and isotopically distinct source values are essential for this process. The δ18OPO4 values of animal wastes have, up to now, received little attention.MethodsPhosphate (PO4) was extracted from cattle faeces using anion resins and the contribution of microbial PO4 was assessed. The δ18OPO4 value of the extracted PO4 was measured by precipitating silver phosphate and subsequent analysis on a thermal conversion elemental analyser at 1400°C, with the resultant carbon monoxide being mixed with a helium carrier gas passed through a gas chromatography (GC) column into a mass spectrometer. Faecal water oxygen isotope ratios (δ18OH2O values) were determined on a dual‐inlet mass spectrometer through a process of headspace carbon dioxide equilibration with water samples.ResultsMicrobiological results indicated that much of the extracted PO4 was not derived directly from the gut fauna lysed during the extraction of PO4 from the faeces. Assuming that the faecal δ18OH2O values represented cattle body water, the predicted pyrophosphatase equilibrium δ18OPO4 (Eδ18OPO4) values ranged between +17.9 and +19.9‰, while using groundwater δ18OH2O values gave a range of +13.1 to +14.0‰. The faecal δ18OPO4 values ranged between +13.2 and +15.3‰.ConclusionsThe fresh faecal δ18OPO4 values were equivalent to those reported elsewhere for agricultural animal slurry. However, they were different from the Eδ18OPO4 value calculated from the faecal δ18OH2O value. Our results indicate that slurry PO4 is, in the main, derived from animal faeces although an explanation for the observed value range could not be determined.

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Advances in Using Oxygen Isotope Ratios of Phosphate to Understand Phosphorus Cycling in the Environment

Cited by 52 publications

References 172 publications

Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes

Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes

Phosphorus availability and turnover in the Chesapeake Bay: Insights from nutrient stoichiometry and phosphate oxygen isotope ratios

The stable oxygen isotope ratio of resin extractable phosphate derived from fresh cattle faeces

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