Development and initial application of δ18Op to understand phosphorus cycling in river, lake and groundwater ecosystems.

Variation in the stable isotope composition of oxygen within dissolved phosphate (δ18Op) represents a novel and potentially powerful environmental tracer. In freshwater, marine and terrestrial ecosystems, δ18Op can act as an inherent label for the sources of phosphorus and the extent to which phosphorus from different sources is metabolised. This paper focuses on the methodological development and initial application of δ18Op across a range of freshwater ecosystems. Initially, we report modifications to the analytical protocol for δ18Op that are designed to minimise incorporation of contaminant oxygen in the final silver phosphate precipitate prior to pyrolysis. This is critical given the range of possible sources of contaminant oxygen within freshwater matrices. Subsequently, we consider the potential utility of δ18Op through application of the technique within a range of freshwater ecosystems in England, UK. Firstly, we characterise δ18Op in river water and effluents from Sewage Treatment Works (STW), and examine the opportunity to use the 18Op of STW effluents to trace the entry and downstream fate of phosphorus from these point sources in rivers. Secondly, we analyse δ18Op to gain insights into variations in the sources and biological cycling of phosphorus in a seasonally stratified lake ecosystem. Thirdly, we characterise δ18Op in shallow and deep groundwater samples, considering whether δ18Op might provide evidence for variation in source and extent of metabolism for phosphorus in groundwater ecosystems. Taken together, these data extend the catalogue of δ18Op in freshwater ecosystems, and further the scope of δ18Op as a tool to better understand phosphorus biogeochemistry

A multi-stable isotope framework to understand eutrophication in aquatic ecosystems

Eutrophication is a globally significant challenge facing aquatic ecosystems, associated with human induced enrichment of these ecosystems with nitrogen (N) and phosphorus (P). However, the limited availability of inherent labels for P and N has constrained understanding of the triggers for eutrophication in natural ecosystems and appropriate targeting of management responses. This paper proposes and evaluates a new multi-stable isotope framework that offers inherent labels to track biogeochemical reactions governing both P and N in natural ecosystems. The framework couples highly novel analysis of the oxygen isotope composition of phosphate (δ18OPO4) with dual isotope analysis of oxygen and N within nitrate (δ15NNO3, δ18ONO3) and with stable N isotope analysis in ammonium (δ15NNH4). The River Beult in England is used as an exemplar system for initial evaluation of this framework. Our data demonstrate the potential to use stable isotope labels to track the input and downstream fate of nutrients from point sources, on the basis of isotopic differentiation for both P and N between river water and waste water treatment work effluent (mean difference = +1.7‰ for δ18OPO4; +15.5‰ for δ15NNH4 (under high flow); +7.3‰ for δ18ONO3 and +4.4‰ for δ15NNO3). Stable isotope data reveal nutrient inputs to the river upstream of the waste water treatment works that are consistent with partially denitrified sewage or livestock sources of nitrate (δ15NNO3 range = +11.5 to +13.1‰) and with agricultural sources of phosphate (δ18OPO4 range = +16.6 to +19.0‰). The importance of abiotic and metabolic processes for the in-river fate of N and P are also explored through the stable isotope framework. Microbial uptake of ammonium to meet metabolic demand for N is suggested by substantial enrichment of δ15NNH4 (by 10.2‰ over a 100 m reach) under summer low flow conditions. Whilst the concentration of both nitrate and phosphate decreased substantially along the same reach, the stable isotope composition of these ions did not vary significantly, indicating that concentration changes are likely driven by abiotic processes of dilution or sorption. The in-river stable isotope composition and the concentration of P and N were also largely constant downstream of the waste water treatment works, indicating that effluent-derived nutrients were not strongly coupled to metabolism along this in-river transect. Combined with in-situ and laboratory hydrochemical data, we believe that a multi-stable isotope framework represents a powerful approach for understanding and managing eutrophication in natural aquatic ecosystems

Genetic complexity of miscanthus cell wall composition and biomass quality for biofuels

BACKGROUND: Miscanthus sinensis is a high yielding perennial grass species with great potential as a bioenergy feedstock. One of the challenges that currently impedes commercial cellulosic biofuel production is the technical difficulty to efficiently convert lignocellulosic biomass into biofuel. The development of feedstocks with better biomass quality will improve conversion efficiency and the sustainability of the value-chain. Progress in the genetic improvement of biomass quality may be substantially expedited by the development of genetic markers associated to quality traits, which can be used in a marker-assisted selection program. RESULTS: To this end, a mapping population was developed by crossing two parents of contrasting cell wall composition. The performance of 182 F1 offspring individuals along with the parents was evaluated in a field trial with a randomized block design with three replicates. Plants were phenotyped for cell wall composition and conversion efficiency characters in the second and third growth season after establishment. A new SNP-based genetic map for M. sinensis was built using a genotyping-by-sequencing (GBS) approach, which resulted in 464 short-sequence uniparental markers that formed 16 linkage groups in the male map and 17 linkage groups in the female map. A total of 86 QTLs for a variety of biomass quality characteristics were identified, 20 of which were detected in both growth seasons. Twenty QTLs were directly associated to different conversion efficiency characters. Marker sequences were aligned to the sorghum reference genome to facilitate cross-species comparisons. Analyses revealed that for some traits previously identified QTLs in sorghum occurred in homologous regions on the same chromosome. CONCLUSION: In this work we report for the first time the genetic mapping of cell wall composition and bioconversion traits in the bioenergy crop miscanthus. These results are a first step towards the development of marker-assisted selection programs in miscanthus to improve biomass quality and facilitate its use as feedstock for biofuel production

Stable carbon Isotope evidence for neolithic and bronze age crop water management in the eastern mediterranean and southwest asia

In a large study on early crop water management, stable carbon isotope discrimination was determined for 275 charred grain samples from nine archaeological sites, dating primarily to the Neolithic and Bronze Age, from the Eastern Mediterranean and Western Asia. This has revealed that wheat (Triticum spp.) was regularly grown in wetter conditions than barley (Hordeum sp.), indicating systematic preferential treatment of wheat that may reflect a cultural preference for wheat over barley. Isotopic analysis of pulse crops (Lens culinaris, Pisum sativum and Vicia ervilia) indicates cultivation in highly varied water conditions at some sites, possibly as a result of opportunistic watering practices. The results have also provided evidence for local land-use and changing agricultural practices

Low 15N/14N ratios for nitrate in snow in the High Arctic (791N).

We report on the 15N/14N and 18O/16O ratio analysis of nitrate in accumulated winter snowpack and fresh spring snow collected near Ny A( lesund, Svalbard (791N), in the early summers of 2001–2003. The presence of contaminant organic matter in the silver nitrate prepared for analysis must be carefully monitored to assess its effects on d15N, and particularly d18O results. d15N values ranged 18% to 7% (versus air N2) and d18O values +60 to +85% (versus VSMOW). The d18O values are in the reported range for atmospheric nitrate in other parts of the globe, and will tend to reflect the relationship between NOy oxygen and H2O þ O2 in the troposphere immediately prior to nitrate deposition. d15N values, however, are lower than those for atmospheric nitrate over most parts of the globe, but show similarities to 15N/14N ratios reported for atmospheric nitrate in the Antarctic. We discuss mechanisms for producing 15N-depleted nitrate in the troposphere, or the possibility that it reflects NOy nitrogen derived from the stratosphere

Comparison of two Late Quaternary interglacials using stable isotopes: the record from Lake Pamvotis, Ioannina, NW Greece

No description supplie

Isotopic fingerprint for phosphorus in drinking water supplies

Phosphate dosing of drinking water supplies, coupled with leakage from distribution networks, represents a significant input of phosphorus to the environment. The oxygen isotope composition of phosphate (δ18OPO4), a novel stable isotope tracer for phosphorus, offers new opportunities to understand the importance of phosphorus derived from sources such as drinking water. We report the first assessment of δ18OPO4 within drinking water supplies. Forty samples from phosphate-dosed distribution networks were analysed from across England and Wales. In addition, samples of the source orthophosphoric acid used for dosing were also analysed. Two distinct isotopic signatures for drinking water were identified (average = +13.2‰ or +19.7‰), primarily determined by δ18OPO4 of the source acid (average = +12.4‰ or +19.7‰). Depending on the source acid used, drinking water δ18OPO4 appears isotopically distinct from a number of other phosphorus sources. Isotopic offsets from the source acid ranging from -0.9‰ to +2.8‰ were observed. There was little evidence that equilibrium isotope fractionation dominated within the networks, with offsets from temperature-dependent equilibrium ranging from -4.8‰ to +4.2‰. Whilst partial equilibrium fractionation may have occurred, kinetic effects associated with microbial uptake of phosphorus or abiotic sorption and dissolution reactions may also contribute to δ18OPO4 within drinking water supplies

Using delta15N and delta18O to evaluate the sources and pathways of NO3 - in rainfall event discharge from drained agricultural grassland lysimeters at high temporal resolutions

The origin of NO yielded in drainage from agricultural grasslands is of environmental significance and has three potential sources; (i) soil organic mater (SOM), (ii) recent agricultural amendments, and (iii) atmospheric inputs. The variation in 15N-NO and 18O-NO was measured from the inter-flow and drain-flow of two 1 ha drained lysimeter plots, one of which had received an application of 21 m3 of NH-N-rich agricultural slurry, during two rainfall events. Drainage started to occur 1 month after the application of slurry. The concentrations of NO-N from the two lysimeters were comparable; an initial flush of NO-N occurred at the onset of drainage from both lysimeters before levels quickly dropped to <1 mg NO-N L-1. The isotopic signature of the 15N-NO and 18O-NO during the first two rainfall events showed a great deal of variation over short time-periods from both lysimeters. Isotopic variation of 15N-NO during rainfall events ranged between -1.6 to +5.2 and +0.4 to +11.1 from the inter-flow and drain-flow, respectively. Variation in the 18O-NO ranged from +2.0 to +7.8 and from +3.3 to +8.4. No significant relationships between the 15N-NO or 18O-NO and flow rate were observed in most cases although 18O-NO values indicated a positive relationship and 15N-NO values a negative relationship with flow during event 2. Data from a bulked rainfall sample when compared with the theoretical 18O-NO for soil microbial NO indicated that the contribution of rainfall NO accounted for 8% of the NO in the lysimeter drainage at most. The calculated contribution of rainfall NO was not enough to account for the depletion in 15N-NO values observed during the duration of the rainfall event 2. The relationship between 15N-NO and 18O-NO from the drain-flow indicated that denitrification was causing enrichment in the isotopes from this pathway. The presence of slurry seemed to cause a relative depletion in 18O-NO in the inter-flow and 15N-NO in the drain-flow compared with the zero-slurry lysimeter. This may have been caused by increased microbial nitrification stimulated by the presence of increased NH-N

∆¹³C results for cereals grains from Tell Brak samples grouped by chronological period.

<p>Bars indicate means and standard deviations. <b>○</b> = glume wheat and <b>◇</b> = barley.</p