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Showing 1 to 20 of 28 for “"Nitrogen isotopes"”.
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Nitrogen isotopes in chlorophyll and the origin of Eastern Mediterranean sapropels
… to establish methods for the determination of nitrogen and carbon isotope ratios in marine particulate and sedimentary chlorophyll derivatives; (2) to establish chlorophyll δ15N and δl3C as proxies for the nitrogen and carbon isotopic composition of marine phytoplankton; and (3) to use …
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Nitrogen isotopes in chlorophyll and the origin of Eastern Mediterranean sapropels
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.
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A paleoenvironmental reconstruction of the Elands Bay area using carbon and nitrogen isotopes in tortoise bone
This study explores the utility of stable light isotopes in Chersina angulata (angulate or bowsprit tortoise) bone collagen as a paleoenvironmental proxy, to augment the limited range of proxies preserved in Southern Africa. δ¹³C and δ¹⁵N were measured in 76 archaeological tortoises from Elands Bay …
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Stable Carbon and Nitrogen Isotopes of Shell Bound organic Matter, Implications for Modern and Ancient Food Web Dynamics
<p>Stable isotopes are an important tool for solving biogeochemical problems and have been increasingly applied in ecosystem studies because of their utility as source-to-sink tracers and for ecological information. Elements like C and N have more than one stable isotope, and their isotopic …
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Identifying long term patterns and drivers of vegetation structure in an African savanna using stable carbon and nitrogen isotopes
… This study aims to investigate vegetation and Nitrogen cycling changes over time in a diverse patch mosaic landscape in Hluhluwe-iMfolozi Park to identify drivers of vegetation structure and their dynamism over time. Sediment from a 150cm core (taken using a Russian corer) was analyzed for …
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Nitrogen cycling in the subtropical southeast Atlantic and southwest Indian Oceans as recorded by the nitrogen isotopes of modern planktic foraminifera
Despite the importance of nitrogen (N) for ocean productivity, and the long history of using fossil foraminifera to reconstruct past ocean conditions, it is only in recent years, due to methodological advances, that the nitrogen isotope ratio (δ15N) of foraminifera has become a viable proxy for …
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Can nitrogen isotopes be used to detect the effects of burning on nitrogen cycling? : a study on Pinus resinosa in Minnesota, USA
… and coarse roots from stands were analysed for nitrogen isotopes in an attempt to determine if fire effects nitrogen cycling. Fire increased the % nitrogen of coarse roots and changed the ratio of C: N. It may also decrease the depth of the A-horizon. It did not however affect the nitrogen …
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Can nitrogen isotopes be used to detect the effects of burning on nitrogen cycling? A study on Pinus resinosa in Minnesota, USA
… and coarse roots from stands were analysed for nitrogen isotopes in an attempt to determine if fire effects nitrogen cycling. Fire increased the % nitrogen of coarse roots and changed the ratio of C: N. It may also decrease the depth of the A-horizon. It did not however affect the nitrogen …
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Diet and subsistence patterns in the later iron age of South Africa : an analysis of stable carbon and nitrogen isotopes and the incidence of dental caries
Current archaeological perspectives on the change in Later Iron Age diet and subsistence patterns and the subsequent affect on the economy, are re-examined using isotopic and caries analyses. Existing perspectives have focused mainly on material archaeological evidence and are not reflective of …
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Early evolution of environments and metabolism: insights from nitrogen, selenium and sulfur isotopes
… this hypothesis through analyses of selenium isotopes and abundances. After establishing a new analytical technique, I show that selenium was mobilized by oxidative weathering in the late Archean, concurrently with sulfur. Because of selenium's high redox potential, these results confirm the …
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Stable isotope analysis as an indicator of tree and grass rooting depth in a mesic African savanna
… canopy cover and analysed by means of carbon nitrogen isotopes. While δ¹⁵N showed little pattern due to complexities in the fractionation process, δ¹³C revealed that tree and grass rooting depths did not adhere to separate niches as proposed by Walter (1971). Root material from both growth …
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Can the pathway of abalone aquaculture effluent be traced using carbon and nitrogen stable isotope analysis of kelp Ecklonia maxima and mussels Mytilus galloprovincialis?
… Jacobsbaai can be traced using stable carbon and nitrogen isotopes. Kelp (Ecklonia maxima) and blue mussels (Mytilus galloprovincialis) along the coast near the farm (in Jacobsbaai) were collected from 8 sites and used as tracers of the farms effluent. A ninth site was sample in another bay …
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Investigating Environmental Change Due To Hypoxic Conditions On The Louisiana Continental Shelf: A Geochemical Approach
… as well as a trend of increasingly enriched nitrogen isotopes, which is probably caused by a combination of large amounts of denitrification, either within the Mississippi watershed or on the continental shelf, increased primary productivity, compounded with relatively minor increases of …
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Monitoring the influx of marine derived Nitrogen and characterizing soil food webs of riparian zones of the Elwha River Watershed, WA, USA.
<p>Nitrogen is often the most limiting nutrient to productivity in terrestrial ecosystems, and can have large effects on ecosystem processes. Two sources of nitrogen to Pacific Northwest riparian areas are marine derived nitrogen (MDN) via anadromous pacific salmon and symbiotic nitrogen fixation …
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Development and application of isotopically-selective assays for nitric oxide metabolites.
… discrimination between the [14]N and [15]N isotopes, [15]N nitrite was detectable at isotopic ratios of greater than 1:20 [15]N : [14]N. The time of analysis, excluding derivatisation by the Griess assay, was approximately 5 minutes. The method will be useful in metabolic tracer studies …
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Investigating 1500 Years of Dietary Change in the Lower Ica Valley, Peru Using an Isotopic Approach
… A.D.) - have been analysed for stable carbon and nitrogen isotopes. The combination of multiple tissues has allowed analysis at the intra-individual as well as the intra- and inter-group levels creating a detailed and nuanced dietary reconstruction that incorporates dietary information about …
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An Ecological Approach to Feed Management in Fish Rearing Ponds
… through time (Chapter 2). Stable carbon and nitrogen isotopes further revealed that live prey entirely supported fish growth in all feeding treatments during weeks 1–3, and then live prey and the dry feed equally supported further fish growth in the fed ponds (Chapter 3). Although adding feed …
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Climate proxies in planktic foraminifera: Environmental or biomineralisation controls?
… past climate. Numerous trace elements and isotopes in foraminiferal fossils have been applied as proxies to reconstruct ocean environments over geological time. However, the proxy-environment correlations often vary among species and individuals, indicating different degrees of biological …
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Assessing Thule Inuit impacts on High Arctic lakes and ponds : a paleolimnological approach
… average for the High Arctic. Elevated levels of nitrogen and phosphorus were observed in the pond indicating the continuing influence of nutrient inputs centuries after the abandonment of the camp. Meanwhile, on Bathurst Island, the orientation of the Deblicquy site, such that the large majority …
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Changes in δ¹⁵N in pastoral soils under varying management intensity
In New Zealand, nitrogen (N) inputs and losses have increased dramatically following establishment (and subsequent intensification) of European style pastoral agriculture from the 1800s. An indicator that could identify soils which are most vulnerable to N loss would be useful to help target …
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