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Articles 1 - 7 of 7
Full-Text Articles in Life Sciences
Neodymium Isotopic Signature Of The Deep Western Boundary Current And The Distribution Of Neodymium Isotopes And Concentrations Across Line W, Brian Daniel Duggan
Neodymium Isotopic Signature Of The Deep Western Boundary Current And The Distribution Of Neodymium Isotopes And Concentrations Across Line W, Brian Daniel Duggan
Theses and Dissertations
The capacity of the neodymium (Nd) 143Nd/144Nd ratio to trace modern ocean circulation accurately allows for the assumption that the ratio can also accurately trace paleo ocean circulation. Therefore, a complete understanding of Nd cycling and its effect on the isotopic composition in the oceans is vital. Traditionally, Nd isotopic composition (Nd IC) is considered a conservative property in the open ocean, while coastal and margin environments tend to be dictated by nonconservative exchange processes. However, Nd concentrations ([Nd]) in the open ocean typically display a nutrient like profile, increasing with depth. Such a discrepancy between Nd IC and [Nd] …
Climatic Controls On Organic Matter Decomposition In Boreal Peatlands, Michael J. Philben
Climatic Controls On Organic Matter Decomposition In Boreal Peatlands, Michael J. Philben
Theses and Dissertations
Boreal peatlands currently contain 550 Pg C and are located at high latitudes where mean annual temperatures are expected to increase by as much as 7°C by the end of the century. There is growing concern that warming will stimulate decomposition, transforming peatlands from a sink to a source of atmospheric carbon dioxide and accelerating climate change. A primary goal of this dissertation was to evaluate the effect of climate change on organic matter decomposition in peatlands. This was achieved by developing and employing biochemical tracers to indicate the extent of peat decomposition across a range of naturally occurring climatic …
Geochemical Analysis Of Eolian Fluxes During The Transition From Greenhouse To Icehouse Conditions In Equatorial Pacific., Daniel Nicholas Miller
Geochemical Analysis Of Eolian Fluxes During The Transition From Greenhouse To Icehouse Conditions In Equatorial Pacific., Daniel Nicholas Miller
Theses and Dissertations
To assess the atmospheric conditions during times of differing pole to equator thermal gradients through the middle Eocene to early Oligocene, 42 to 30 Ma, samples from deep-sea sediment cores U1331, U1332, U1333 from IODP Expedition 320/321 in the eastern equatorial Pacific (EEP) have been chemically leached to isolate the operationally defined eolian dust (ODED; <63 μm fraction). The ODED was analyzed for neodymium (Nd) isotopic compositions and rare earth element (REE) concentrations in order to determine the provenance of the ODED fraction and to elucidate the environmental conditions (e.g. predominant wind patterns) during deposition over the interval of study. The variations in the ODED fraction are expected to be controlled by changes in sources delivered via eolian input. However, negative cerium anomalies in the Post Achaean Australian Shale (PAAS) normalized rare earth element profiles of the ODED show a biasing geochemical seawater phase to the ODED signature. It is found that εNd values and cerium anomalies (Ce/Ce*) of ODED are consistent with fossil fish teeth values that record bottom water signatures from the same location and time period until ~36-37 Ma; around the Priabonian/Bartonian boundary marked by increased thermal gradients due to the emplacement of high elevation glaciers on Antarctica (Scher et. al., 2014). Moreover, the more negative cerium anomalies correlate to more radiogenic εNd values. The geochemical seawater signature in the ODED samples is believed to be caused by a change in sedimentary phase regulated by the spatial paleoposition of the sites relative to the biological high productivity zone and/or the depth of the CCD. Subsequently these regulators on the sedimentary phases of the ODED were investigated for biasing the geochemical signatures of the ODED, assumed to be changes in sources thereby provenance. Together, the Nd and REE results from the study temporally indicate that the ODED fraction may be a mixing between two sources, that of a biasing biogenic and/or authigenic source that records seawater conditions, and that of an older, less radiogenic continental source, inferred as Asian loess, as an increased thermal gradient prevails over the course of the study. Further research needs to be performed to make more robust and conclusive linkages between sources, mixing of sources, and atmospheric eolian delivery patterns, highlighting the necessity for a better understanding of atmospheric conditions during important climatic events throughout the history of the Earth.
The Effects Of Aeration On Phytoplankton Community Composition And Primary Production In Stormwater Detention Ponds Near Myrtle Beach, Sc, Lauren Hehman
Theses and Dissertations
Stormwater detention ponds are a common approach to managing stormwater runoff in coastal South Carolina. While effective at preventing flooding, they can be sites of intense phytoplankton blooms that result from excess nutrients inputs. This can lead to water quality degradation within ponds from oxygen depletion, fish kills, health concerns from harmful algal blooms (HABs), and water quality deterioration in adjacent coastal waters when pond discharges. The most common management practice to rid the ponds of excess phytoplankton biomass is the addition of copper-based algaecides. While temporarily effective, these algaecides require regular re-application and lead to artificial cycles of productivity …
A Study On Atmospheric And Oceanic Processes In The North Indian Ocean, Clifford Steven Felton
A Study On Atmospheric And Oceanic Processes In The North Indian Ocean, Clifford Steven Felton
Theses and Dissertations
Studies on oceanic and atmospheric processes in the Indian Ocean are an active and important area of scientific research. Understanding how intraseasonal and interannual variations impact both the ocean and atmosphere will aid in delineating potential feedback mechanisms and global teleconnections. Thanks to recent efforts focused on expanding observational capabilities and developing models for this region, researchers have been able to begin investigating atmospheric and oceanic processes in the Indian Ocean. This study focuses on the impact of the El Niño Southern Oscillation (ENSO) on tropical cyclone activity over the Bay of Bengal (BoB) and on developing a method for …
The Composition And Downward Vertical Transport Of Particulate Phosphorus In The Cariaco Basin, Venezuela, Anne S. Opseth
The Composition And Downward Vertical Transport Of Particulate Phosphorus In The Cariaco Basin, Venezuela, Anne S. Opseth
Theses and Dissertations
In order to understand the biogeochemical cycling of phosphorus (P) in a coastal marine ecosystem, the chemical composition and the sinking flux of particulate P was analyzed within sediment trap particles collected in the Cariaco Basin, Venezuela. Total, inorganic and organic P composition was examined across the time series (1995-2010) using a modified Aspila method and sequential extraction techniques. Particulate inorganic P (PIP) dominated the total particulate P (TPP) pool (~52%) when averaged over the entire water column. Relationships between particulate nitrogen (PN) and particulate organic carbon (POC) fluxes versus TPP fluxes followed expected canonical Redfield ratios except for a …
Reproductive Success In Hatchery-Produced Eastern Oyster, Crassostrea Virginica (Gmelin), April Piggott
Reproductive Success In Hatchery-Produced Eastern Oyster, Crassostrea Virginica (Gmelin), April Piggott
Theses and Dissertations
The eastern oyster (Crassostrea virginica Gmelin 1791) has great ecological and economic importance but populations have declined, especially in Chesapeake Bay, to historically low numbers. Hatcheries strive to produce oysters with beneficial characteristics for supplementation and commercial purposes, both natural and stimulated mass spawning. Unequal contribution of parents in mass spawnings potentially can lead to high levels of inbreeding and a loss of beneficial characteristics in offspring. In this study, we determined microsatellite genotypes for parents (n^parents =24, 49, and 77 parents) and progeny (n=96 each) of three hatchery-produced families and used the data for parental assignment. We observed the …