Nutrient inputs from productive marine environments have been shown to directly and indirectly subsidise primary producers and consumers in terrestrial ecosystems (e.g. Polis and Hurd 1995; 1996; Anderson and Polis 1998; 1999). But does this theory hold true on islands surrounded by oligotrophic waters, which account for a significant proportion of the marine environment? The aim of the present study was to examine the applicability of the spatial subsidisation hypotheses proposed by Polis and his co-authors to an oligotrophic system in south-western region of Western Australia. These aims were achieved by comparing soil and plant nutrients, and the nitrogen stable isotope signatures of soil, plants, detritus and invertebrates in areas with (islands) and without (mainland sites) inputs from seabirds. In addition, the responses of plant nutrients and vegetation assemblages to guano additions were examined in a controlled field experiment.

This thesis investigates stable isotope signals (i.e. δ18O and δ2H) in various information carriers such as lake water and lacustrine sediments, aiming to develop and refine the use of isotope tracers in hydrology and paleohydrology studies. Located at the confluence of the Peace and Athabasca Rivers at the western end of Lake Athabasca, the PAD is a key node in the Mackenzie River Drainage system, the single large freshwater source discharging into the Arctic Ocean from continental Northern America. The delta is one of the world’s largest freshwater deltas, has hundreds of shallow lakes and wetlands, and has been regularly monitored for isotopic composition in surface water bodies over a 7-year period. Because of the hydrological significance of the delta, as well as the availability of a wealth of ancillary information collected by previous studies, the PAD serves as a natural laboratory to develop and refine the application of stable isotopes in understanding landscape hydrological conditions in present and past. The outcomes also provide critical information for the development of scientifically informed management strategies for water resources in the delta. In the study of modern processes, a novel coupled isotope tracer method was developed to characterize the isotopic composition of input water to lakes. The method is based on coupling the well-known Craig-Gordon model, which describes the evaporative enrichment process for both isotopes, with the Local Meteoric Water Line to constrain the isotopic composition of input water to lakes. The application of this method in two sampling campaigns (2000 and 2005) demonstrated significant temporal changes in source water to PAD lakes at landscape scale. The results also revealed the previously underestimated role of snowmelt to the northern part of the delta. In a laboratory culture experiment, effort was undertaken to understand the constant fractionation between aquatic cellulose and environmental water, which is routinely observed in field studies. This led to the development of a new conceptual characterization of the apparent cellulose-water relation that reconciles discrepancies among previous observations. This new interpretation supports the notion that oxygen in cellulose is fully inherited from CO₂during photosynthesis, but that aquarium studies may incorporate an unintended artefact from CO₂that has not undergone complete biochemically mediated exchange with water. The variable slope of the cellulose-water δ18O relation observed in culture experiments is attributed to varying degree of exchange, related to the residence time of CO₂in the water. This is in contrast to natural systems where long residence time of CO₂is likely to ensure full exchange, thus supporting the application of a constant apparent cellulose-water oxygen isotope fractionation in paleoenvironmental studies. Insights gained from these studies were applied in a multiproxy paleolimnological investigation of a shallow lake in the central part of the delta near the shoreline of Lake Athabasca. The Craig-Gordon modelling approach was applied to quantitative interpretation of a cellulose d18O record from lake sediments. Constraints provided by interpretation of other proxies allowed the development of a semi-quantitative assessment of changes in lake water balance over the past one thousand years. The inferred hydrological history indicated significant shifts in the source of water to the lake, including persistent influence from Lake Athabasca during the Little Ice Age (~ AD 1540-1880), as well as rapid change during the last century that is unprecedented in the last millennium. Overall, the thesis demonstrates our improved understanding of hydrological conditions based on various isotopic archives such as lake water and aquatic cellulose. New information acquired from these studies concerning the range and rate of hydrological variability in the present and past provides a fundamental baseline for evaluating the potential impacts of future climate change and human disturbance in the Peace-Athabasca Delta.

Hamilton Harbour, a semi-enclosed bay located at the western end of Lake Ontario, is listed as one of the most polluted systems in the Great Lakes. Anthropogenic influences such as four wastewater treatment plants, two steel mills and shoreline development have lead to degradation of this system. A Remedial Action Plan is in place to clean up the harbour by 2015. This study examined the food web dynamics of Hamilton Harbour including 21 species of fish, benthic invertebrates, plankton and macrophytes. Using carbon and nitrogen stable isotopes spatial and seasonal variability throughout the harbour was examined. Zooplankton and phytoplankton collected at three different sites in the harbour showed no significant difference spatially but did show seasonal trends, reaching the highest nitrogen values in early summer. Benthic invertebrates, when observed in δ13C: δ15N biplots, group together by sampling site in each season. Seasonally benthic invertebrates acquire higher nitrogen signatures in summer then decrease in fall at all sites. The fish community in the harbour do not have spatially distinct isotope signatures. Seasonally nitrogen signatures increased at all sites while carbon signatures remained between -25 ‰ and -26 ‰. Overall the plankton and benthic invertebrate nitrogen isotope signatures are higher than the fishes. This indicates that there is a recent change in nutrient source. The likely candidate for nutrient input is an anthropogenic source, such as the wastewater treatment plants discharging into the harbour. Isotope signatures show large variation in fish species collected indicating that the fishes are omnivore generalists that take advantage of available food sources throughout the harbour. Further remediation work, such as habitat modifications, can now be tailored towards generalist omnivores that move throughout the harbour.

This thesis investigates stable isotope signals (i.e. δ18O and δ2H) in various information carriers such as lake water and lacustrine sediments, aiming to develop and refine the use of isotope tracers in hydrology and paleohydrology studies. Located at the confluence of the Peace and Athabasca Rivers at the western end of Lake Athabasca, the PAD is a key node in the Mackenzie River Drainage system, the single large freshwater source discharging into the Arctic Ocean from continental Northern America. The delta is one of the world’s largest freshwater deltas, has hundreds of shallow lakes and wetlands, and has been regularly monitored for isotopic composition in surface water bodies over a 7-year period. Because of the hydrological significance of the delta, as well as the availability of a wealth of ancillary information collected by previous studies, the PAD serves as a natural laboratory to develop and refine the application of stable isotopes in understanding landscape hydrological conditions in present and past. The outcomes also provide critical information for the development of scientifically informed management strategies for water resources in the delta. In the study of modern processes, a novel coupled isotope tracer method was developed to characterize the isotopic composition of input water to lakes. The method is based on coupling the well-known Craig-Gordon model, which describes the evaporative enrichment process for both isotopes, with the Local Meteoric Water Line to constrain the isotopic composition of input water to lakes. The application of this method in two sampling campaigns (2000 and 2005) demonstrated significant temporal changes in source water to PAD lakes at landscape scale. The results also revealed the previously underestimated role of snowmelt to the northern part of the delta. In a laboratory culture experiment, effort was undertaken to understand the constant fractionation between aquatic cellulose and environmental water, which is routinely observed in field studies. This led to the development of a new conceptual characterization of the apparent cellulose-water relation that reconciles discrepancies among previous observations. This new interpretation supports the notion that oxygen in cellulose is fully inherited from CO₂during photosynthesis, but that aquarium studies may incorporate an unintended artefact from CO₂that has not undergone complete biochemically mediated exchange with water. The variable slope of the cellulose-water δ18O relation observed in culture experiments is attributed to varying degree of exchange, related to the residence time of CO₂in the water. This is in contrast to natural systems where long residence time of CO₂is likely to ensure full exchange, thus supporting the application of a constant apparent cellulose-water oxygen isotope fractionation in paleoenvironmental studies. Insights gained from these studies were applied in a multiproxy paleolimnological investigation of a shallow lake in the central part of the delta near the shoreline of Lake Athabasca. The Craig-Gordon modelling approach was applied to quantitative interpretation of a cellulose d18O record from lake sediments. Constraints provided by interpretation of other proxies allowed the development of a semi-quantitative assessment of changes in lake water balance over the past one thousand years. The inferred hydrological history indicated significant shifts in the source of water to the lake, including persistent influence from Lake Athabasca during the Little Ice Age (~ AD 1540-1880), as well as rapid change during the last century that is unprecedented in the last millennium. Overall, the thesis demonstrates our improved understanding of hydrological conditions based on various isotopic archives such as lake water and aquatic cellulose. New information acquired from these studies concerning the range and rate of hydrological variability in the present and past provides a fundamental baseline for evaluating the potential impacts of future climate change and human disturbance in the Peace-Athabasca Delta.

Hamilton Harbour, a semi-enclosed bay located at the western end of Lake Ontario, is listed as one of the most polluted systems in the Great Lakes. Anthropogenic influences such as four wastewater treatment plants, two steel mills and shoreline development have lead to degradation of this system. A Remedial Action Plan is in place to clean up the harbour by 2015. This study examined the food web dynamics of Hamilton Harbour including 21 species of fish, benthic invertebrates, plankton and macrophytes. Using carbon and nitrogen stable isotopes spatial and seasonal variability throughout the harbour was examined. Zooplankton and phytoplankton collected at three different sites in the harbour showed no significant difference spatially but did show seasonal trends, reaching the highest nitrogen values in early summer. Benthic invertebrates, when observed in δ13C: δ15N biplots, group together by sampling site in each season. Seasonally benthic invertebrates acquire higher nitrogen signatures in summer then decrease in fall at all sites. The fish community in the harbour do not have spatially distinct isotope signatures. Seasonally nitrogen signatures increased at all sites while carbon signatures remained between -25 ‰ and -26 ‰. Overall the plankton and benthic invertebrate nitrogen isotope signatures are higher than the fishes. This indicates that there is a recent change in nutrient source. The likely candidate for nutrient input is an anthropogenic source, such as the wastewater treatment plants discharging into the harbour. Isotope signatures show large variation in fish species collected indicating that the fishes are omnivore generalists that take advantage of available food sources throughout the harbour. Further remediation work, such as habitat modifications, can now be tailored towards generalist omnivores that move throughout the harbour.

In this thesis, we are interested in using the Padé approximants and asymptotic series to approximate the density functions of the stable distributions. The paper specifically discusses the selection of the optimal degree and central point of Padé approximants as well as how to connect the Padé approximants and asymptotic series as a piecewise function. Based on such approximation, a computational algorithm is developed to estimate the maximum likelihood estimator with confidence interval of the parameters, using quasi-Newton method. Simulations are conducted to evaluate the performance of this algorithm, and comparisons are made to Nolan's integral method to show that the method introduced in the thesis is fast and reliable in approximation and estimation.

Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Spawning capelin (Mallotus villosus) provide a pulse resource of fish eggs and dead fish on the northeast Newfoundland coast, bringing an abundance of nutrients into the system that can be relied upon by numerous predatory and scavenging species. I investigated how this annual resource pulse influenced the diet and distribution of green sea urchins (Strongylocentrotus droebachiensis) at capelin spawning sites and the potential for urchins to impact capelin recruitment through egg predation. Urchin density was monitored using a remotely operated vehicle (ROV) during the summers of 2013 and 2014, and urchins were collected from capelin spawning sites in 2014 to assess diet using nitrogen and carbon stable isotopes. Urchins were distributed in higher densities in areas with dead capelin and were often clumped directly on dead fish. Conversely, the presence of capelin eggs negatively influenced urchin density. Stable isotope analysis revealed an increase in 15N when capelin resources became available, suggesting urchins were consuming capelin resources. Diet preference experiments also indicated that dead capelin were preferentially consumed over eggs. Overall, urchins appear to prefer and seek out dead capelin on spawning sites suggesting urchins may be important recyclers of capelin detritus and have little impact on capelin recruitment. / October 2015

No description available.