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Alves, J. O. S. "Open-ocean deep convection : understanding and parametrization." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262034.
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Back, Larissa. "Towards an improved understanding of deep convection patterns over the tropical oceans /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10062.
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Makowski, Jessica. "Understanding Transport Variability of the Antarctic Circumpolar Current Using Ocean Bottom Pressure." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4915.
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Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). The OBP observations from the Gravity Recovery and Climate Experiment (GRACE) are used to calculate transport along the choke point between Antarctica and Australia. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set.
There has been some evidence to suggest that Southern Hemisphere winds and the Southern Annular Mode (SAM) or the Antarctic Oscillation (AAO) play a significant role in accelerating/decelerating ACC transport, along with some contribution from buoyancy forcing. We will examine whether average zonal wind stress, wind stress curl, local zonal winds, or the SAM are representative of the low frequency zonal mass transport variability.
Preliminary studies suggest that seasonal variation in transport across the Australia-Antarctica choke point is driven by winds along and north of the northern front of the ACC, the Sub Tropical front (STF). It also appears that interannual variations in transport are related to wind variations centered south of the Sub Antarctic Front (SAF). We have observed a strong negative correlation/positive correlation across the STF of the ACC in the Indian Ocean, which suggests wind stress curl may also be responsible for transport variations.
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Bates, Stephanie. "Barium uptake by foraminifera : understanding past and present ocean processes." Thesis, University of Bristol, 2016. http://hdl.handle.net/1983/c12eed98-50c4-421f-8a79-af2f292fa971.
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Oceanic barium can provide multiple insights into the marine environment, an important facet of the climate system. Dissolved barium is removed from near-surface seawater in association with biological productivity and is returned at depth via remineralisation and barite dissolution, imparting a nutrient-like profile similar to that of carbonate alkalinity and silica. Due to the similarity in their distributions, seawater barium and alkalinity display a positive linear relationship globally and different water masses have distinct barium-alkalinity compositions. Benthic foraminiferal Ba/Ca ratios can thus be used as a proxy for past ocean circulation and alkalinity, but this may be complicated by additional environmental influences, particularly in non-pelagic settings. In addition, a specific barium partition coefficient may be required for each individual species. Glacial-interglacial changes have been successfully measured using benthic Ba/Ca ratios but many possible applications have yet to be explored to the same extent, such as comparisons between interglacial periods. Barium isotope ratios (δ138Ba) can also be used to enhance our understanding of the marine environment, but because this is a relatively new technique there is still much to be learned regarding the oceanic distribution of barium isotopes and the relationship between seawater and foraminifer δ138Ba is not yet known. An essential prerequisite to measuring either Ba/Ca or δ138Ba ratios in foraminifera is the removal of particulate barite from their inner and outer surfaces. Although a cleaning technique has been established, this has sometimes increased foraminiferal Ba/Ca ratios, perhaps due to the preferential dissolution of low-barium calcium carbonate. During this project these topics were investigated using sediment cores from the southeast and southwest Atlantic Ocean dated to the Holocene and Marine Isotope Stage 5e (MIS 5e, part of the last interglacial period), as well as seawater and foraminifer samples of modern age from the tropical North Atlantic. Ba/Ca ratios in a continental shelf sediment core remain approximately constant despite apparent fluctuations in primary productivity, suggesting that the Ba/Ca proxy can reliably be used as a proxy for ocean circulation even in relatively shallow and productive regions. The effect of dissolution on Ba/Ca could not be assessed due to the absence of dissolution effects in this sediment core. New barium partition coefficients are presented for the benthic foraminifer species Melonis barleeanus, Oridorsalis umbonatus and Uvigerina peregrina. These are offset from one another, highlighting the potential importance of using species-specific partition coefficients. In other sediment cores from the southwest Atlantic, MIS 5e Ba/Ca ratios are on average significantly higher than those of the Holocene. This may be due to a ‘stagnation event’ in Antarctic Bottom Water (AABW) formation during MIS 5e which led to a build-up of dissolved barium in AABW. In samples from the tropical North Atlantic Ocean, seawater δ138Ba appears to be controlled by conservative mixing at depths below ~500 m, with additional non-conservative controls in the upper ~500 m. δ138Ba ratios in the planktic foraminifer Orbulina universa are consistently isotopically lighter than seawater, but the magnitude of this offset is variable. This variability may be due to morphotype-specific vital effects on δ138Ba ratios. Although cleaning tests provide indirect evidence for barite removal, the impact of cleaning on Ba/Ca ratios remains variable and the cause of this variability remains an open question. Collectively, the findings presented here have implications for the uses of Ba/Ca and δ138Ba ratios as palaeoceanographic proxies, as well as for the possible mechanisms of climatic variability in MIS 5e and the Holocene.
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Kim, Jong-Mun. "Connecting children to the ocean : understanding elementary students' changes in ocean literacy during a marine aquarium summer camp experience." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/47054.
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Relatively little research has been carried out on how to increase ocean literacy among students from diverse sociocultural backgrounds in both formal and informal educational contexts. To contribute to the pressing need for research in this important area, this study employed a mixed methods approach and examined changes in elementary students’ (Grades 3 to 5) ocean literacy during a five-day summer camp (AquaCamps) experience provided by the Vancouver Aquarium. A specially developed survey questionnaire, interview protocol, in-camp observations, and document analysis methods were used to collect data on the characteristics of changes in students’ ocean literacy as well as the influences of AquaCamps and other life experiences on the changes in their marine science knowledge and orientations (naturalistic, aesthetic, recreational, utilitarian, and negativistic).
Quantitative analysis of the survey data revealed appreciable changes in students’ marine science knowledge and in their orientations. In particular, students’ marine science knowledge and naturalistic, aesthetic, and recreational orientations increased while utilitarian and negativistic orientations decreased after participating in AquaCamps.
Qualitative data analysis elucidated AquaCamps program components that influenced these changes. The analysis also revealed additional sources including family members and multimedia, which affected changes in students’ ocean literacy. A noteworthy finding of this study is students’ limited understanding of their connections to the ocean and marine organisms as a whole.
This study highlights the need for marine education to focus on building individual student’s ocean literacy by (1) helping individual students to explicitly understand how they are connected to ocean/marine organisms and (2) providing individual students with opportunities to build emotional connections to ocean/marine organisms through direct encounters.
This study’s findings have implications for theory and practice in the field of marine education and provide a basis for offering suggestions on ways marine aquarium education might foster students’ ocean literacy.
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Liu, Wei [Verfasser], and Nico [Akademischer Betreuer] Sneeuw. "Understanding ocean tide aliasing in satellite gravimetry / Wei Liu ; Betreuer: Nico Sneeuw." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1192305272/34.
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Cockrell, Kevin L. "Understanding and utilizing waveguide invariant range-frequency striations in ocean acoustic waveguides." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65275.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), February 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 163-170).<br>Much of the recent research in ocean acoustics has focused on developing methods to exploit the effects that the sea surface and seafloor have on acoustic propagation. Many of those methods require detailed knowledge of the acoustic properties of the seafloor and the sound speed profile (SSP), which limits their applicability. The range-frequency waveguide invariant describes striations that often appear in plots of acoustic intensity versus range and frequency. These range-frequency striations have properties that depend strongly on the frequency of the acoustic source and on distance between the acoustic source and receiver, but that depend mildly on the SSP and seafloor properties. Because of this dependence, the waveguide invariant can be utilized for applications such as passive and active sonar, time-reversal mirrors, and array processing, even when the SSP or the seafloor properties are not well known. This thesis develops a framework for understanding and calculating the waveguide invariant, and uses that framework to develop signal processing techniques for the waveguide invariant. A method for passively estimating the range from an acoustic source to a receiver is developed, and tested on experimental data. Heuristics are developed to estimate the minimum source bandwidth and minimum horizontal aperture required for range estimation. A semi-analytic formula for the waveguide invariant is derived using WKB approximation along with a normal mode description of the acoustic field in a rangeindependent waveguide. This formula is applicable to waveguides with arbitrary SSPs, and reveals precisely how the SSP and the seafloor reflection coefficient affect the value of the waveguide invariant. Previous research has shown that the waveguide invariant range-frequency striations can be observed using a single hydrophone or a horizontal line array (HLA) of hydrophones. This thesis shows that traditional array processing techniques are sometimes inadequate for the purpose of observing range-frequency striations using a HLA. Array processing techniques designed specifically for observing range-frequency striations are developed and demonstrated. Finally, a relationship between the waveguide invariant and wavenumber integrations is derived, which may be useful for studying range-frequency striations in elastic environments such as ice-covered waveguides.<br>by Kevin L. Cockrell.<br>Ph.D.
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Takano, Yohei. "Understanding the mechanisms of dissolved oxygen trends and variability in the ocean." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54994.
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A widely observed tracer in the field of oceanography is dissolved oxygen (O2). A tracer crucial to ocean biogeochemical cycles, O2 plays an active role in chemical processes, marine life, and ecosystems. Recent advances in observation and numerical simulation have introduced opportunities for furthering our understanding of the variability and long-term changes in oceanic O2. This work examines the underlying mechanisms driving O2 variability and long-term changes. It focuses on two distinct time-scales: intra-seasonal variability (i.e., a time scale of less than a month) and centennial changes in O2. The first half of this work analyzes state-of-the-art observations from a profiling float in an investigation of the mechanisms driving the intra-seasonal variability of oceanic O2. Observations from the float show enhanced intra-seasonal variability (i.e., a time scale of about two weeks) that could be driven by isopycnal heaving resulting from internal waves or tidal processes. Observed signals could result from aliased signals from internal waves or tides and should be taken into account in analyses of the growing observational dataset. The methods proposed in this study may be useful for future analyses of high-frequency tracer variability associated with mesoscale and sub-mesoscale processes. Using outputs from state-of-the-art earth system models and a suite of sensitivity experiments based on a general circulation and biogeochemistry ocean model, the second half of this work focuses on investigating mechanisms regulating centennial changes in O2. It explores the aspect of anthropogenic climate change (e.g., changes in the sea surface temperature and wind stress fields) that significantly impacts oceanic O2, focusing specifically on tropical oxygen minimum zones. Results suggest that ocean heating induces a water mass shift, leads to decrease apparent oxygen utilization (AOU) in the tropical thermocline. The AOU decrease compensates the effect of decrease in oxygen saturation due to the ocean warming. Our sensitivity experiments show that both physically (i.e., age) and biologically (i.e., the oxygen utilization rate) driven AOU will contribute almost equally to controlling changes in oceanic O2 in the next century. However, additional sensitivity experiments indicate that physically and biologically driven AOU balance has regional characteristics. We need to address the unanswered question of how varying large-scale oceanic circulations regulate this balance and answer fundamental questions that lead to a more comprehensive understanding of the mechanisms that control the variability and the future evolution of oceanic O2.
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Cooper, Rachel. "OCEAN ACIDIFICATION: UNDERSTANDING THE COASTAL CARBON PUMP IN A HIGH CO2 WORLD." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/420.
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Since the 1800s, carbon dioxide emissions due to human activities have contributed significantly to the amount of carbon in the atmosphere. Approximately a third of this carbon is absorbed by the ocean, through air-sea fluxes at the ocean surface (Sabine, 2004). Increased CO2 has changed the carbon chemistry of the ocean and hence the pH. pH is expected to drop by 0.4 by the year 2100. It is unclear how this lower pH will affect carbon cycling and sequestration with respect to the biological carbon pump. Most studies have focused on open ocean phytoplankton or bacterial communities in large, stationary mesocosms. Few studies have coupled both phytoplankton and bacterial processes and even fewer have investigated coastal communities, where pH and pCO2 can vary drastically. This study focused first on developing and evaluating a mesocosm and alternative method for elevating pCO2. The second goal was to determine how potential changes in phytoplankton DOC release and community structure and the resulting carbon pool may affect bacterial secondary production and ectoenzyme activity in a natural coastal community. Mesocosms aimed to mimic natural pCO2 fluctuations by maintaining CO2 concentration of 1250 ppm in the headspace, as aqueous pCO2 may change with biological processes. Six mesocosms were filled with 40L of water from the Chesapeake Bay (three ambient pCO2 and three 1250 ppm) and monitored over 15 days. Chlorophyll a, DOC, bacterial respiration, bacterial production, and enzyme activity were measured. Bacterial production and respiration were used to calculate bacterial growth efficiency (BGE). Results showed that there was no significant difference between the ambient and elevated groups with respect to chlorophyll a, DOC, BGE and enzymes activity. However, differences in bacterial respiration and bacterial production during the first four days of the experiment may suggest that bacteria require time to acclimate to elevated pCO2. Phytoplankton and bacteria in coastal areas are exposed to a wide range of abiotic factors such as seasonal temperature variations, salinity, mixing, and terrestrial inputs. The pH of the Chesapeake Bay ranges between 7.5 and 8.3, and it is possible that the phytoplankton and bacteria are adapted to cope with a wide range of pH (Wong, 2012). This study suggests that the biological carbon pump may not be significantly altered in our future ocean.
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Levine, Naomi Marcil. "Understanding the ocean carbon and sulfur cycles in the context of a variable ocean : a study of anthropogenic carbon storage and dimethylsulfide production in the Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57553.
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Thesis (Ph.D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student submitted PDF version of thesis.<br>Includes bibliographical references.<br>Anthropogenic activity is rapidly changing the global climate through the emission of carbon dioxide. Ocean carbon and sulfur cycles have the potential to impact global climate directly and through feedback loops. Numerical modeling, field and laboratory studies are used to improve our mechanistic understanding of the impact of natural variability on carbon and sulfur cycling. Variability in ocean physics, specifically changes in vertical mixing, is shown to significantly impact both cycles. The impact of interannual variability on the detection and attribution of anthropogenic carbon (Canthro) and the storage of Canthro in the Atlantic Ocean is analyzed using a three-dimensional global ocean model. Several regions are identified where empirical methods used to estimating Canthro are not able to correct for natural variability in the ocean carbon system. This variability is also shown to bias estimates of long term trends made from hydrographic observations. In addition, the storage of Canthro in North Atlantic mode waters is shown to be strongly influenced by water mass transformation during wintertime mixing events. The primary mechanisms responsible for seasonal variability in dimethylsulfoniopropionate (DMSP) degradation and dimethylsulfide (DMS) production in the oligotrophic North Atlantic are investigated using potential enzyme activity and gene expression and abundance data. Vertical mixing and UV radiative stress appear to be the dominant mechanisms behind seasonal variability in DMS production in the Sargasso Sea. This thesis demonstrates the importance of and dynamics of bacterial communities responsible for DMSP degradation and DMS production in oligotrophic surface waters. These findings suggest that modifications to current numerical models of the upper ocean sulfur cycle may be needed. Specifically, current static parameterizations of bacterial DMSP cycling should be replaced with a dynamic bacterial component including DMSP degradation and DMS production.<br>by Naomi Marcil Levine.<br>Ph.D.
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Scales, Kylie Lisa. "The application of ocean front metrics for understanding habitat selection by marine predators." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3319.
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Marine predators such as seabirds, cetaceans, turtles, pinnipeds, sharks and large teleost fish are essential components of healthy, biologically diverse marine ecosystems. However, intense anthropogenic pressure on the global ocean is causing rapid and widespread change, and many predator populations are in decline. Conservation solutions are urgently required, yet only recently have we begun to comprehend how these animals interact with the vast and dynamic oceans that they inhabit. A better understanding of the mechanisms that underlie habitat selection at sea is critical to our knowledge of marine ecosystem functioning, and to ecologically-sensitive marine spatial planning. The collection of studies presented in this thesis aims to elucidate the influence of biophysical coupling at oceanographic fronts – physical interfaces at the transitions between water masses – on habitat selection by marine predators. High-resolution composite front mapping via Earth Observation remote sensing is used to provide oceanographic context to several biologging datasets describing the movements and behaviours of animals at sea. A series of species-habitat models reveal the influence of mesoscale (10s to 100s of kilometres) thermal and chlorophyll-a fronts on habitat selection by taxonomically diverse species inhabiting contrasting ocean regions; northern gannets (Morus bassanus; Celtic Sea), basking sharks (Cetorhinus maximus; north-east Atlantic), loggerhead turtles (Caretta caretta; Canary Current), and grey-headed albatrosses (Thalassarche chrysostoma; Southern Ocean). Original aspects of this work include an exploration of quantitative approaches to understanding habitat selection using remotely-sensed front metrics; and explicit investigation of how the biophysical properties of fronts and species-specific foraging ecology interact to influence associations. Main findings indicate that front metrics, particularly seasonal indices, are useful predictors of habitat preference across taxa. Moreover, frontal persistence and spatiotemporal predictability appear to mediate the use of front-associated foraging habitats, both in shelf seas and in the open oceans. These findings have implications for marine spatial planning and the design of protected area networks, and may prove useful in the development of tools supporting spatially dynamic ocean management.
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Ansorge, I. J., Pierre William Froneman, J. R. E. Lutjeharms, et al. "An interdisciplinary cruise dedicated to understanding ocean eddies upstream of the Prince Edward Islands." South African Journal of Science, 2004. http://hdl.handle.net/10962/d1007566.
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A detailed hydrographic and biological survey was carried out in the region of the South-West Indian Ridge during April 2004. Altimetry and hydrographic data have identified this region as an area of high flow variability. Hydrographic data revealed that here the Subantarctic Polar Front (SAF) and Antarctic Polar Front (APF) converge to form a highly intense frontal system. Water masses identified during the survey showed a distinct separation in properties between the northwestern and southeastern corners. In the north-west, water masses were distinctly Subantarctic (>8.5°C, salinity >34.2), suggesting that the SAF lay extremely far to the south. In the southeast corner water masses were typical of the Antarctic zone, showing a distinct subsurface temperature minimum of <2.5°C. Total integrated chl-a concentration during the survey ranged from 4.15 to 22.81 mg chl-a m[superscript (-2)], with the highest concentrations recorded at stations occupied in the frontal region. These data suggest that the region of the South-West Indian Ridge represents not only an area of elevated biological activity but also acts as a strong biogeographic barrier to the spatial distribution of zooplankton.
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Gregor, Luke. "Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25320.
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The Southern Ocean plays an important role in mitigating the effects of anthropogenically driven climate change. The region accounts for 43% of oceanic uptake of anthropogenic carbon dioxide (CO₂). This is foreseen to change with increasing greenhouse gas emissions due to ocean chemistry and climate feedbacks that regulate the carbon cycle in the Southern Ocean. Studies have already shown that Southern Ocean CO₂ is subject to interannual variability. Measuring and understanding this change has been difficult due to sparse observational data that is biased toward summer. This leaves a crucial gap in our understanding of the Southern Ocean CO₂ seasonal cycle, which needs to be resolved to adequately monitor change and gain insight into the drivers of interannual variability. Machine learning has been successful in estimating CO₂ in may parts of the ocean by extrapolating existing data with satellite measurements of proxy variables of CO₂. However, in the Southern Ocean machine learning has proven less successful. Large differences between machine learning estimates stem from the paucity of data and complexity of the mechanisms that drive CO₂. In this study the aim is to reduce the uncertainty of estimates, advance our understanding of the interannual drivers, and optimise sampling of CO₂ in the Southern Ocean. Improving the estimates of CO₂ was achieved by investigating: the impact of increasing the gridding resolution of input data and proxy variables, and Support vector regression (SVR) and Random Forest Regression (RFR) as alternate machine learning methods. It was found that the improvement gained by increasing gridding resolution was minimal and only RFR was able to improve on existing error estimates. Yet, there was good agreement of the seasonal cycle and interannual trends between RFR, SVR and estimates from the literature. The ensemble mean of these methods was used to investigate the variability and interannual trends of CO₂ in the Southern Ocean. The interannual trends of the ensemble confirmed trends reported in the literature. A weakening of the sink in the early 2000's, followed by a strengthening a strengthening of the sink into the early 2010's. Wind was the overall driver of dominant decadal interannual trends, being more important during winter due to the increased efficacy of entrainment processes. Summer interannual variability of CO₂ was driven primarily by chlorophyll, which responded to basin scale changes in drivers by the complex interaction with underlying physics and possibly sub-mesoscale processes. Lastly CO₂ sampling platforms, namely ships, profiling floats and moorings, were tested in an idealised simulated model environment using a machine learning approach. Ships, simulated from existing cruise tracks, failed to adequately resolve CO₂ below the uncertainty threshold that is required to resolve the seasonal cycle of Southern Ocean CO₂. Eight high frequency sampling moorings narrowly outperformed 200 profiling floats, which were both able to adequately resolve the seasonal cycle. Though, a combination of ships and profiling floats achieved the smallest error.
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Li, Lingwei. "Understanding Antarctic Circumpolar Current Transport at the LGM Using an Isotope-enabled Ocean Model." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555594394056462.
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Page, Tessa. "Understanding the Molecular and Physiological Responses of Tropical Coralline Algae to a Changing Ocean." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/406520.
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Coral reefs are amongst the most biologically diverse ecosystems on our planet, supporting the livelihoods of millions of people globally. Despite their economic and ecological importance, human-driven global change is posing a major threat to the integrity of coral reefs worldwide. Ocean warming (OW) and ocean acidification (OA), both brought on by increased atmospheric CO2, are adversely affecting coral reefs and the organisms that inhabit them, particularly those organisms that calcify. Crustose coralline algae (CCA) are calcifying red macroalgae that provide essential ecosystem functions to coral reefs worldwide. CCA help to build and stabilise the coral reef framework and contribute to reef resilience and recovery by inducing the settlement of coral larvae to the reef. Previous research has shown CCA to be vulnerable to OW and OA, with resulting changes to their physiology and biology (i.e., reductions in calcification, abundance, survival). However, research on CCA lags behind other coral reef organisms, particularly in terms of their acclimatisation potential and knowledge of molecular, cellular, and metabolic processes. Given the known vulnerability of CCA, urgent research is required to understand how CCA will respond across molecular and physiological levels to global change drivers and this could directly aid in reef restoration efforts.
The first data chapter of my thesis (Chapter 2) provides previously missing molecular information for CCA. De novo transcriptomes were compiled for four species, Porolithon cf. onkodes, Sporolithon cf. durum, Lithophyllum cf. insipidum, and Lithothamnion proliferum, that commonly occur in Australia’s Great Barrier Reef (GBR). Analyses of orthologous genes were conducted between CCA species and two noncalcifiying red algae, Chondrus crispus and Gracilariopsis chorda. Functional enrichment analysis of CCA orthologous proteins revealed a higher-than-expected number of sequences in categories relating to regulation of biological and cellular processes, such as actin related proteins, heat shock proteins, and adhesion proteins. This study allowed me to create reference transcriptomes that can be used in future studies investigating molecular responses of CCA to OW and OA and offered insight into the evolution of coralline algae.
In Chapter 3 I investigated the differential physiological and transcriptomic responses of two species of CCA, P. cf. onkodes and S. cf. durum, to global change drivers (OW and OA). Previous literature investigating the responses of CCA species to global change drivers found variable results and these have been largely speciesspecific. The two species used in this study have been documented to have contrasting responses to OW and OA. Species-specific responses were seen in both the metabolic rate measurements and in the number of differentially expressed genes (DEGs) detected, indicating resilience in one species and not in the other. This study was also the first to reveal pathways and proteins that are differentially regulated in response to global change drivers. This work will help to predict the fate and functioning of different CCA species in future ocean conditions.
Early life history stages of organisms are thought to be more impacted by climatic stressors than their adult stages, therefore, I investigated the responses across different life history stages of the CCA species S. cf. durum to varying levels of temperature and pCO2 (Chapter 4). In this study, I used adults and germlings of their first generation (F1). The findings suggest that adult stages of S. cf. durum are largely robust to end of century levels of temperature and pH, in terms of their survival and metabolic rates, and indicate that adult stages may be able to acclimatise to global change. On the other hand, the data show early life history stages of this species are highly sensitive to global change stressors with reductions in their survival and growth. This could impact the persistence of this species in future oceans.
How an acclimation history to predicted, future levels of temperature and/or pH affects the physiological responses to chronic and acute thermal stress was investigated in the last chapter of my thesis (Chapter 5). P. cf. onkodes was acclimated to chronic, varying levels of temperature and pH for 6 weeks and then subjected to an acute, increasing temperature experiment (+ 4 – 6 ºC). The findings from this study suggest that an acclimation history to elevated temperature will reduce the thermal tolerance of P. cf. onkodes to withstand anomalous temperature events, which are projected to increase in number and severity within this century.
Overall, the findings of the work described in this thesis have: 1) Made available the first comprehensive and annotated de novo transcriptomes for any species of CCA; 2) shown that physiological and transcriptomic response to global change drivers is species specific, with some CCA being more resilient and others not, and identified proteins relating to physiological processes that are differentially expressed in response to stress; 3) supported the hypothesis that early life history stages of CCA will be more impacted by global change drivers than adults of the same species, with possible plasticity being seen in adults in response to sustained exposure to stress; and 4) determined an acclimation history of elevated temperature will reduce thermal tolerance and productivity in CCA. My thesis also provides evidence that more anciently diverged genera (e.g., Sporolithon) are physiologically more robust and molecularly less responsive to global change drivers. My thesis demonstrates the strength of incorporating molecular, life history stage, and acclimation type approaches to more holistically understand the future of a critical group of reef-building organisms under global climate change and will ultimately contribute to conservation efforts that are currently being made into saving coral reefs worldwide.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Environment and Sc<br>Science, Environment, Engineering and Technology<br>Full Text
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張健緯 and Kin-wai Cheung. "Understanding and forecasting interannual variability of tropical cyclone activity in the Western North Pacific Ocean." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31215105.
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Mongwe, Ndunisani Precious. "Understanding modelled sea-air CO2 flux biases in the Southern Ocean through the seasonal cycle." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29260.
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The Southern Ocean forms a vital component of the earth system as a sink of CO2 and heat, taking over 40% of the annual oceanic CO2 uptake (75% of global heat uptake), slowing down the accumulation of CO2 in the atmosphere and thus the rate of climate change. However, recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth System Models (ESMs) show that CMIP5 ESMs disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation estimates in the Southern Ocean. Notwithstanding these differences, the seasonal cycle is a dominant mode of CO2 variability in the Southern Ocean, and hence this is an important bias. Previous studies suggest that these biases of FCO2 in ESMs might be a significant limitation to the long-term simulation of CO2 characteristics in the Southern Ocean. Consequently, this study has three primary objectives: first, to develop a process-based diagnostic method to analyze and isolate key biases and their underlaying mechanisms in the model-observations seasonal cycle of FCO2 differences for forced ocean models and ESMs. Second, to use this framework to examine sources of biases responsible for the limited skill of CMIP5 models in simulating the seasonal cycle of FCO2 with respect to observed estimates. Thirdly, to investigate how these present-day biases in the seasonality and drivers of CO2 in CMIP5 ESMs affect modelled longterm changes in the mechanisms of CO2 uptake in the Southern Ocean. In the first part of the dissertation, an objective diagnostic framework was established to analyze model-observation biases in the seasonal scale of FCO2 using the NEMO PISCES ORCA2LP model output, and Takahashi et al. (2009) observed estimates. The diagnostic framework focuses on examining the relative contributions of the competing drivers (SST and DIC) and related processes (solubility, biological and mixing) to instantaneous monthly changes in surface pCO2 (and FCO2) at the seasonal scale. In the second part of the dissertation, this approach is applied to 10 CMIP5 models in the Southern Ocean, to investigate the mechanistic basis for the seasonal cycle of FCO2 biases. It was found that FCO2 biases in CMIP5 models can be grouped into two main categories, i.e. group-SST and group-DIC. Group-SST models are characterized by an exaggeration of the seasonal rates of change of Sea Surface Temperature (SST) in autumn and spring during the cooling and warming peaks, respectively. These faster-than-observed rates of change of SST tip the control of the seasonal cycle of pCO2 and FCO2 towards SST and result in divergence between the observed and modelled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM2-ES and MPI-ESM, collectively the group-DIC models) compensate the solubility bias because of their exaggerated primary production, such that biologically-driven DIC changes become the regulators of the seasonal cycle of FCO2. It was also found that despite significant differences in the spatial characteristics of the mean annual fluxes, CMIP5 models show a zonal homogeneity in the seasonal cycle of FCO2 at the basin-scale in contrast to observed estimates. In the final third of the dissertation, using five CMIP5 ESMs from the RCP8.5 scenario, it was found that CMIP5 models present climate biases in the seasonality and drivers of FCO2 are fundamental to how models simulate long-term changes in the mechanisms of CO2 uptake in the Southern Ocean. Although all five analyzed models show an increased annual mean CO2 uptake by the end of the century, they show significant differences in the mechanisms. The present-day temperature biased models (group-SST) generally maintain the dominance of the temperature driver in the seasonal variability of FCO2 to end of the century. But show enhanced CO2 uptake due to increased anthropogenic atmospheric CO2 and decreased surface CO2 buffering capacity but they display a weak to null role of biological activity in the increased CO2 sink. On the other hand, the increased CO2 uptake at the end of the century in group-DIC models is explained increased biological driven CO2 uptake in spring, linked to increased Revelle factor and solubility driven CO2 uptake in winter. Increased Revelle factor at the end of the century enhance pCO2 changes for even smaller DIC changes.
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Cheung, Kin-wai. "Understanding and forecasting interannual variability of tropical cyclone activity in the Western North Pacific Ocean /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2036488X.
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Borile, Federica <1991>. "Towards a broader understanding of the effects of tidal forcing on the global ocean circulation." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10329/1/PhD_THESIS_Borile_def.pdf.
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The study of tides and their interactions with the complex dynamics of the global ocean represents a crucial challenge in ocean modelling. This thesis aims to deepen this study from a dynamical point of view, analysing what are the tidal effects on the general circulation of the ocean. We perform different experiments of a mesoscale-permitting global ocean model forced by both atmospheric fields and astronomical tidal potential, and we implement two parametrizations to include in the model tidal phenomena that are currently unresolved, with particular emphasis to the topographic wave drag for locally dissipating internal waves.
An additional experiment using a mesoscale-resolving configuration is used to compare the simulated tides at different resolutions with observed data. We find that the accuracy of modelled tides strongly depends on the region and harmonic component of interest, even though the increased resolution allows to improve the modelled topography and resolve more intense internal waves.
We then focus on the impact of tides in the Atlantic Ocean and find that tides weaken the overturning circulation during the analysed period from 1981 to 2007, even though the interannual differences strongly change in both amplitude and phase. The zonally integrated momentum balance shows that tide changes the water stratification at the zonal boundaries, modifying the pressure and therefore the geostrophic balance over the entire basin.
Finally, we describe the overturning circulation in the Mediterranean Sea computing the meridional
and zonal streamfunctions both in the Eulerian and residual frameworks. The circulation is characterised by different cells, and their forcing processes are described with particular emphasis to the role of mesoscale and a transient climatic event. We complete the description of the overturning circulation giving evidence for the first time to the connection between meridional and zonal cells.
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Mei, M. Jeffrey(Ming-Yi Jeffrey). "Morphological approaches to understanding Antarctic Sea ice thickness." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129062.
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Thesis: Ph. D., Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Department of Aeronautics and Astronautics; and the Woods Hole Oceanographic Institution), 2020<br>Cataloged from student-submitted PDF of thesis.<br>Includes bibliographical references (pages 181-198).<br>Sea ice thickness has long been an under-measured quantity, even in the satellite era. The snow surface elevation, which is far easier to measure, cannot be directly converted into sea ice thickness estimates without knowledge or assumption of what proportion of the snow surface consists of snow and ice. We do not fully understand how snow is distributed upon sea ice, in particular around areas with surface deformation. Here, we show that deep learning methods can be used to directly predict snow depth, as well as sea ice thickness, from measurements of surface topography obtained from laser altimetry. We also show that snow surfaces can be texturally distinguished, and that texturally-similar segments have similar snow depths. This can be used to predict snow depth at both local (sub-kilometer) and satellite (25 km) scales with much lower error and bias, and with greater ability to distinguish inter-annual and regional variability than current methods using linear regressions. We find that sea ice thickness can be estimated to <20% error at the kilometer scale. The success of deep learning methods to predict snow depth and sea ice thickness suggests that such methods may be also applied to temporally/spatially larger datasets like ICESat-2.<br>by M. Jeffrey Mei.<br>Ph. D.<br>Ph.D. Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Department of Aeronautics and Astronautics; and the Woods Hole Oceanographic Institution)
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Schlegel, Robert William. "Coastal marine heatwaves: Understanding extreme forces." University of the Western Cape, 2017. http://hdl.handle.net/11394/6445.
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Philosophiae Doctor - PhD (Biodiversity and Conservation Biology)<br>Seawater temperature from regional to global scale is central to many measures of biodi-
versity and continues to aid our understanding of the evolution and ecology of biolog-
ical assemblages. Therefore, a clear understanding of the relationship between marine
biodiversity and thermal structures is critical for effective conservation planning. In the an-
thropocene, an epoch characterised by anthropogenic forcing on the climate system, future
patterns in biodiversity and ecological functioning may be estimated from projected climate
scenarios however; absent from many of these scenarios is the inclusion of extreme thermal
events, known as marine heatwaves (MHWs). There is also a conspicuous absence in knowl-
edge of the drivers for all but the most notorious of these events.
Before the drivers of MHWs along the coast of South Africa could be determined, it was first
necessary to validate the 129 in situ coastal seawater temperature time series that could be
used to this end. In doing so it was found that time series created with older (longer), lower
precision (0.5 Degrees Celsius) instruments were more useful than newer (shorter) time series produced
with high precision (0.001 Degrees Celsius) instruments. With the in situ data validated, a history of the
occurrence of MHWs along the coastline (nearshore) was created and compared against
MHWs detected by remotely sensed data (offshore). This comparison showed that the
forcing of offshore temperatures onto the nearshore was much lower than anticipated,
with the rates of co-occurrence for events between the datasets along the coast ranging
from 0.2 to 0.5. To accommodate this lack of consistency between datasets, a much larger
mesoscale area was then taken around southern Africa when attempting to determine
potential mesoscale drivers of MHWs along the coast. Using a self organising-map (SOM), it
was possible to organise the synoptic scale oceanographic and atmospheric states during
coastal MHWs into discernible groupings. It was found that the most common synoptic
oceanographic pattern during coastal MHWs was Agulhas Leakage, and the most common
atmospheric pattern was anomalously warmoverland air temperatures.With these patterns
known it is now necessary to calculate how often they occur when no MHW has been
detected. This work may then allow for the development of predictive capabilities that could help mitigate the damage caused by MHWs.
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Wang, Faming. "Toward understanding predictability of climate: a linear stochastic modeling approach." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1147.
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This dissertation discusses the predictability of the atmosphere-ocean climate system on interannual and decadal timescales. We investigate the extent to which the atmospheric internal variability (weather noise) can cause climate prediction to lose skill; and we also look for the oceanic processes that contribute to the climate predictability via interaction with the atmosphere.
First, we develop a framework for assessing the predictability of a linear stochastic system. Based on the information of deterministic dynamics and noise forcing, various predictability measures are defined and new predictability-analysis tools
are introduced. For the sake of computational efficiency, we also discuss the formulation
of a low-order model within the context of four reduction methods: modal, EOF, most predictable pattern, and balanced truncation.
Subsequently, predictabilities of two specific physical systems are investigated within such framework.
The first is a mixed layer model of SST with focus on the effect of oceanic advection.Analytical solution of a one-dimensional model shows that even though advection can give rise to a pair of low-frequency normal modes, no enhancement in the predictability is found in terms of domain averaged error variance. However, a Predictable Component Analysis (PrCA) shows that advection can play a role in redistributing the predictable variance. This analytical result is further tested in a more realistic two-dimensional North Atlantic model with observed mean currents.
The second is a linear coupled model of tropical Atlantic atmosphere-ocean system. Eigen-analysis reveals that the system has two types of coupled modes: a decadal meridional mode and an interannual equatorial mode. The meridional mode, which manifests itself as a dipole pattern in SST, is controlled by thermodynamic feedback between wind, latent heat flux, and SST, and modified by ocean heat transport. The equatorial mode, which manifests itself as an SST anomaly in the eastern equatorial basin, is dominated by dynamic feedback between wind, thermocline, upwelling, and SST. The relative strength of thermodynamic vs dynamic feedbacks determines the behavior of the coupled system, and enables the tropical Atlantic variability to be more predictable than the passive-ocean scenario.
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Ksibe, Amira Z. "Zinc on the move : insights towards understanding zinc homeostasis in the open ocean cyanobacterium Synechococcus sp. WH8102." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/89711/.
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Since the discovery of zinc as an essential element for living organisms including humans, animals, plants, fungi and bacteria, much has been learnt about zinc in biological systems, ranging from its effects at the whole organism level, including the uptake/efflux of zinc, identification of important zinc-regulator proteins, down to structural, thermodynamic, and kinetic details of zinc-protein interactions. One of the most exciting fields to work on, currently, is understanding the importance of zinc “on the move” - in particular the “acquisition and homeostasis” of this micronutrient element by the organisms. In this wider context, zinc homeostasis by open ocean cyanobacteria, which occupy variable ecosystems with an erratic nutrient supply, has become of recent interest. In an attempt to resolve how open ocean cyanobacteria persist in regions where the zinc concentration is thought to be limited, we hypothesised that the cyanobacterium Synechococcus sp. WH8102 might provide an extracellular zinc scavenger for the acquisition of this essential element. Therefore, the current study developed a method to isolate and purify the putative biogenic zinc-binding ligand (zincophore) using polystyrene-divinylbenzene resin and liquid chromatographies. However, it seems likely Synechococcus sp. WH8102 produce ligands that can bind to zinc only under zinc-depleted conditions. Then, we performed zinc limitation and repletion experiments on axenic cultures of marine Synechococcus sp. WH8102, and data determined that this strain mounted an adaptive response for zinc under depleted and replete conditions, resulting in the induction and/or repression of a number of proteins. As a homologue to the Fur family, Zur from Synechococcus sp. WH8102 was sub-cloned and purified in the absence of zinc ions in the cultures. Synechococcus sp. WH8102 Zur protein at neutral pH (~pH 7.8), in mass spectrometry, presented as a mixture of species including a monomer with two zinc ions bound Zn2Zur, a dimer with four zinc ions bound, and another well folded Zn4Zur2 dimer. The complementary technique, ICP-OES, confirmed that the zinc binding stoichiometry was in agreement with mass spectrometric findings, 2.1±0.2 Zn(II) ions per monomer. Mimicking a drop in available cellular zinc as may be expected in zinc-deplete conditions, it was found that only one of the two metal ions bound per monomer was removed by EDTA from Synechococcus sp. WH8102 Zur protein, giving 0.9 ± 0.3 Zn(II) atoms per monomer, with shifting in the monomer/dimer equilibrium toward Zn1Zur species. No large difference in the secondary structure between the metallo-species of the SynZur protein was found in CD spectroscopy. Moreover, Synechococcus sp. WH8102 Zur protein was found to behave in a similar manner to previously studied Fur family proteins, where zinc removal from the sensory site is fully reversible and has the ability to re-establish a (2:1) Zn(II):protein ratio in less than 15 min with 1.9 ± 0.4 Zn(II) atoms per monomer. Similarly, Synechococcus sp. WH8102 Zur was found to act as a transcriptional factor in the presence of zinc ions and bind specifically to 23 AT-rich DNA sequence. The “free” cytosolic zinc concentrations that Zur protein trigger transcription of znuABC and smtA found to be in femtomolar range ~ 1.78 ×10-15, with the dissociation constant ~ 62.65±1.47 nM and 61.76 ± 2.42 nM for Zur-PznuA promoter and SynZur-PsmtA promoter, respectively.
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Freytes-Ortiz, Ileana M. "An Interdisciplinary Approach to Understanding Predator-Prey Relationships in a Changing Ocean: From System Design to Education." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7673.
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Climate change is ecologically and socially complex, deemed the most important issue of our generation. Through this dissertation I have approached climate change research through an interdisciplinary perspective, investigating how this phenomenon will affect marine ecological systems, how we can better develop experimental systems to answer ecological questions, and how we can effectively educate about this issue.
In Chapter 2, I provided accessible alternatives for researching the effects of climate change (elevated temperatures and pCO2) on marine ecosystems. I designed, built, and troubleshooted two accurate and inexpensive climate-controlled experimental systems capable of maintaining target conditions: a temperature-controlled system and an ocean acidification system. The temperature-controlled system was designed to manipulate experimental tank temperatures indirectly by controlling the temperature in a surrounding water bath, which buffered fluctuations and resulted in a high level of control. The ocean acidification experimental system was designed to elevate normally fluctuating pCO2 levels by a constant factor, which allowed pCO2 to fluctuate as expected in natural environments and made it more ecologically relevant than active pCO2-controlled systems.
In Chapter 3, I experimentally tested the morphological responses of southern ribbed mussels Geukensia granosissima to two simultaneous stressors (elevated temperatures and the presence of water-borne predation cues from blue crab Callinectes sapidus) and if any effects of these treatments led to differences in handling times by predatory crabs. Bivalves may become more susceptible to predation as increased temperatures decrease the protection afforded by their shells, but few studies have tested the effects of elevated temperatures on inducible defenses in bivalves. Results showed that chronic heat stress can have detrimental morphological effects on intertidal mussels. Mussels reared in elevated temperatures manifested elongated shell shapes, exhibited a disruption of the predator effect on inducible defenses, and experienced decreased predator handling times. The observed responses to elevated temperatures could make southern ribbed mussels more vulnerable to predation.
In Chapter 4, I experimentally tested the morphological responses of southern ribbed mussels to elevated pCO2 levels and the presence of water-borne predation cues from blue crabs, and if these effects led to differences in handling times by predatory crabs. Elevated pCO2 can have negative effects on bivalves’ morphology and physiology, but the consequences of these effects on predator-prey interactions are still unclear. I found that adult southern ribbed mussels’ inducible defenses were not affected by a medium-term exposure to elevated pCO2. Mussels grew more in shell length and width as a response to predation cues, independent of pCO2 conditions. However, and unexpectedly, mussels reared under elevated pCO2 exhibited greater growth in shell width independent of predator treatment, driving mussels reared in the presence of a predator under elevated pCO2 conditions to develop rounder shapes. On average, these effects on mussel morphometrics did not affect crab handling times, but mussels reared in the presence of a predator under elevated pCO2 conditions had highly variable handling times. It is important to consider the complexity of animal physiology, morphology, and interspecies relationships when making deductions on predator-prey relationships in a changing ocean.
In Chapter 5, I analyzed the effectiveness of using an interdisciplinary approach to climate change education. Literature suggests that an interdisciplinary instructional framework in an outdoor setting, using tools from the experiential, active, and inquiry- and place-based learning approaches, as well as the socioscientific issues pedagogical framework, would be an excellent approach for climate change education. I found that students: increased their content knowledge on climate change causes and consequences, exhibited a deeper understanding of climate change through the words they used to describe it, and corrected common climate change misconceptions. This work can serve as an example for the development of effective climate change programs that uses already available instructional materials with intentional interdisciplinary goals.
Our search to understand how marine ecosystems will cope with a changing climate has emphasized emerging issues in the way we gather data, the questions we seek to answer through research, and how we translate science of social importance to the public. Through this dissertation I strove to seek the answers to some of these questions and provide feasible solutions to some of the problems in climate change research and education through an interdisciplinary approach. As science continues to move towards answering questions of concern for both science and society, science research is moving towards more interdisciplinary approaches. This dissertation is an example of how this can be an efficient and comprehensive approach.
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Kaeli, Jeffrey W. "Computational strategies for understanding underwater optical image datasets." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85539.
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Thesis: Ph. D. in Mechanical and Oceanographic Engineering, Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 117-135).<br>A fundamental problem in autonomous underwater robotics is the high latency between the capture of image data and the time at which operators are able to gain a visual understanding of the survey environment. Typical missions can generate imagery at rates hundreds of times greater than highly compressed images can be transmitted acoustically, delaying that understanding until after the vehicle has been recovered and the data analyzed. While automated classification algorithms can lessen the burden on human annotators after a mission, most are too computationally expensive or lack the robustness to run in situ on a vehicle. Fast algorithms designed for mission-time performance could lessen the latency of understanding by producing low-bandwidth semantic maps of the survey area that can then be telemetered back to operators during a mission. This thesis presents a lightweight framework for processing imagery in real time aboard a robotic vehicle. We begin with a review of pre-processing techniques for correcting illumination and attenuation artifacts in underwater images, presenting our own approach based on multi-sensor fusion and a strong physical model. Next, we construct a novel image pyramid structure that can reduce the complexity necessary to compute features across multiple scales by an order of magnitude and recommend features which are fast to compute and invariant to underwater artifacts. Finally, we implement our framework on real underwater datasets and demonstrate how it can be used to select summary images for the purpose of creating low-bandwidth semantic maps capable of being transmitted acoustically.<br>by Jeffrey W. Kaeli.<br>Ph. D. in Mechanical and Oceanographic Engineering
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Petiteau, Louis. "In situ observations of microbial remineralization in the mesopelagic ocean at spatial and temporal scales : towards a better mechanistic understanding." Electronic Thesis or Diss., Sorbonne université, 2025. http://www.theses.fr/2025SORUS019.
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La quantité de carbone séquestrée par la pompe biologique est en partie contrôlée par les microbes, qui reminéralisent le carbone organique particulaire (COP) transporté vers l'océan profond. Dans la zone mésopélagique, les facteurs de contrôle de la reminéralisation et leur hiérarchie demeurent incompris. Dans le cadre de cette thèse, des régions et saisons contrastées ont été échantillonnées avec le piège à particules / incubateur C-RESPIRE, dans le but d'approfondir notre compréhension de certains de ces facteurs de contrôle sur les taux de dégradation et l'atténuation verticale des flux de COP. Les eaux subantarctiques et polaires de l'océan Australe révèlent des systèmes d'export contrastés suite au bloom printanier malgré des atténuations de flux de COP relativement similaires. On montre que la zone subantarctique est caractérisée par une dominance de particule d'origine fécale et une importante reminéralisation microbienne. Les eaux polaires sont caractérisées par une dominance de phyto-détritus reminéralisés lentement dont l'atténuation est principalement due à la dégradation du zooplancton. La température et le type de particules pourraient expliquer les différentes contributions des microbes aux deux pompes biologiques à carbone régionales. En s'affranchissant des variations de température et à travers la variabilité saisonnière, la reminéralisation in situ de particules exportées par voies gravitationnelle, biologique (i.e., migration du necton) et physique ont été mesurées en mer Méditerranée. Cette série temporelle d'un an est la première à mettre en évidence une forte saisonnalité de la reminéralisation mésopélagique. Nous montrons que les taux de reminéralisation des microbes attachés aux particules sont étroitement liés à la voie d'export prédominante. Ces résultats suggèrent qu'en cas d'export de particules par voies gravitationnelle et physique, les taux de reminéralisation associés diminuent avec la profondeur, tandis que les migrations nycthémérales injectent en profondeur de la matière hautement labile. En Atlantique nord, deux méthodes de mesure des taux de reminéralisation microbien ont été utilisées sur deux classes de taille de particules distinctes. Ces méthodes, mises en œuvre pour la première fois au cours d'une même campagne, montrent des tendances verticales distinctes de taux de reminéralisation, suggérant des dynamiques d'exports différentes entre les deux groupes de particules. Finalement, nous avons rassemblé, l'ensemble des données de reminéralisation microbienne mesurées avec le C-RESPIRE que notre travail a permis de doubler, dans le but d'explorer la hiérarchie d'une partie des facteurs de contrôle identifiés dans la littérature et dans nos travaux. A l'échelle de l'océan global, aucune tendance claire n'émerge, indiquant que les facteurs de contrôle de la reminéralisation sont étroitement interconnectés. Ce résultat interpelle nos méthodes d'observation et souligne l'absence notable de la prise en compte de la diversité des communautés microbiennes comme facteur de contrôle<br>The amount of carbon sequestered by the biological pump is partially regulated by microbes, which remineralize particulate organic carbon (POC) transported to the deep ocean. In the mesopelagic zone, the controlling factors of remineralization and their relative importance remain poorly understood. In this thesis, contrasting regions and seasons were sampled using the particle interceptor/incubator C-RESPIRE to deepen our understanding of some drivers of the remineralization rates and the vertical attenuation of POC fluxes. Following the spring bloom, subantarctic and polar waters of the Southern Ocean reveal contrasting export systems, despite relatively similar POC flux attenuation. We show that the subantarctic zone is characterized by fecally-dominated particles and important microbial remineralization. Polar waters are dominated by slowly remineralized phyto-aggregates and attenuation was primarily driven by zooplankton degradation. Temperature and particle type could explain the different contributions of microbes to the two regional biological carbon pumps. Through seasonal variability, in situ remineralization of particles exported by gravitational, biological (i.e., nekton migration) and physical pathways were measured at approximately constant temperature in the Mediterranean mesopelagic zone. This one-year time-series is the first to demonstrate strong seasonality in mesopelagic remineralization. We show that the remineralization rates of particle-attached microbes are closely linked to the predominant export pathway. These results suggest that when particles are exported by gravitational and physical pathways, their associated remineralization rates decrease with depth, while diurnal migrating zooplankton inject highly labile matter at depth. In the North Atlantic, two methods were used to measure microbial remineralization rates on distinct particle size classes. These methods, implemented for the first time during the same cruise, show distinct vertical trends in remineralization rates, suggesting different export dynamics between the two size classes. Finally, we have gathered all microbial remineralization rates measured with C-RESPIRE, doubled during this thesis, in order to explore the hierarchy of some of the controlling factors identified in the literature and in this work. At the global ocean scale, no clear trends emerge, indicating that the drivers of remineralization are intricately interwoven. This result challenges our observational approaches and highlights the absence of the microbial community diversity as a driver of remineralization
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Cristofari, Robin. "Structure and dynamics of the penguin synnomes : understanding seabird life history and response to climate change through population genomics." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ005/document.
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L’Océan austral est l’un des pivot des écosystèmes et du climat de notre planète, qui concentre plus de 20% de la productivité primaire marine mondiale. La complexité de ses réseaux trophiques et son inaccessibilité rendent plus encore qu’ailleurs nécessaire l’utilisation d’espèces bio-indicatrices. Plusieurs espèces de manchots (comme le Manchot Royal et le Manchot Empereur) sont ainsi l’objet de programmes de suivi à long terme. Dans cette étude, nous utilisons les données offertes par la génomique des populations (« RAD-sequencing » couvrant le génome de centaines d'individus issus couvrant la distribution de ces deux espèces) et les représentations numériques du climat de l’IPCC-CMIP5 pour calibrer dans le temps long les analyses démographique plus précises réalisées à l'échelle de quelques générations dans le cadre de suivis démographiques, et mieux comprendre la réponse des manchots au changement climatique. Au-delà de ses conséquences immédiates pour l’étude des Manchots en tant que sentinelles de l’Océan Austral, cette étude montre l’intérêt d’une plus forte intégration de la génomique des populations dans les études démographiques et comportementales<br>The Southern Ocean plays a central role in the regulation of the Earth’s climate and ecosystems, and accounts for more than 20% of the world’s marine productivity. The complexity of its trohpic networks and its sheer inaccessibility make the use of bioindicator species more necessary there than anywhere else. Several penguin species (such as the King and the Emperor penguin) are therefore the focus of long-term monitoring programs.In this study, we use the information from population genomics (« RAD-sequencing » data covering the genome of hundreds of individuals from the two species’ full distribution) and from IPCC-CMIP5 numerical climate models to calibrate in the long time the more precise demographic analyses realised in the framework of field surveys, and understand penguin responses to cliamte change. Beyond its implications for the study of penguins as sentinels of the Southern Ocean, our work demonstrates the interest of a stronger integration of population genomics in demographic and behavioural investigation
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Wang, Liping. "The dynamic role of ridges in a β-plane channel : towards understanding the dynamics of large scale circulation in the Southern Ocean". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/57741.
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Lucey, Noelle Marie. "Improving our understanding of evolutionary persistence in an increasingly high CO2 world : insight from marine polychaetes at a low pH vent system." Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/6531.
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The main aim of this thesis was to determine how marine metazoans might persist as ocean acidification (OA) conditions intensify. This was done using a combination of field surveys, field transplants and laboratory experiments with polychaetes from a site where volcanically-derived CO2 gas bubbles through the seafloor and drives the seawater pH down, resulting in a marine ecosystem representative of global OA projections for, or before, the year 2100. My first objective was to identify phenotypes, or traits, associated with OA tolerance (Chapter 2 and 5). To do this, I characterized the distribution of dominant calcifying polychaetes along natural pH gradients and used a comparative species recruitment trial to investigate life history traits underlying species’ OA tolerance, or vulnerability. I first found two dominant, closely related species of polychaete: Pileolaria militaris Claparède, 1870 and Simplaria sp. (Serpulidae, Spirorbinae). I then found that increased fecundity and rapid settlement are important traits in determining species’ abilities to persist in low pH environments (Chapter 2). Afterwhich, I investigated the life history traits of the non-calcifying polychaete, Platynereis dumerilii (Audouin & Milne Edwards, 1834), of one of the few species from the low pH site known to have broadcasting, pelagic development. I performed breeding experiments on P. dumerilii collected in both ambient and low pH sites and found that specimens from the low pH site were actually the direct developing brooder sister species, Platynereis massiliensis (Moquin-Tandon, 1869). By reanalayzing the distributions of both species at each site using genetic barcoding, I found clear evidence that direct development and brooding are dominant traits at low pH site, and for OA persistence (Chapter 5). My second objective was to use reciprocal transplant experiments to compare the relative importance of local adaptation and/or plasticity as potential mechanisms responsible for the differential tolerances of populations of the polychaete species Simplaria sp. to low pH. Laboratory transplants indicate that a local adaptation response occurred through genetic accommodation in the Simplaria sp. population from the low pH site. However, neither local adaptation nor plasticity appeared responsible for this species natural low pH persistence when assessed in situ (Chapter 3 & 4). My final objective was to create a framework using the polychaete vent model to identify other types of marine metazoans that are likely to be able to adapt to, and survive, under the predicted environmental conditions (Chapter 5). I overviewed the life history strategies of all dominant polychaetes in the low pH sites, and related trends in their life history strategies to those of other marine invertebrates. Brooding and direct development appear to be key traits for species likely to persist in future oceans pH. I conclude by summarizing how research regarding evolutionary responses may be advanced to add confidence to our projections of future marine metazoan responses.
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Forrer, Heather. "Toward an improved understanding of the Southern Ocean's biological pump: phytoplankton group-specific contributions to nitrogen and carbon cycling across the Subantarctic Indian Ocean." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33675.
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Iron (and silicate) (co-)limitation of phytoplankton is considered a primary cause of the Southern Ocean's inefficient biological pump. However, the role of phytoplankton community structure and response to nutrient cycling remains poorly understood. In a mass balance sense, phytoplankton consumption of new nitrogen (N; e.g., allochthonous nitrate) is proportional to net carbon (C) export, while growth fueled by recycled N (e.g., ammonium) yields no net C flux. The N isotope ratio (δ15N) of surface biomass has long been used as an integrative tracer of new versus regenerated uptake. This approach is rendered more accurate by coupling either fluorescence-activated cell sorting (FACS; of nano- and picophytoplankton; 0.4-20 μm) or microscopy (for microphytoplankton; >20 um) with groupspecific δ15N measurements. Samples were collected for the analysis of nutrients and nitrate-, FACS-, and microscopy-δ15N on a mid-summer transect of the Subantarctic Indian basin during the 2016/17 Antarctic Circumnavigation Expedition (ACE) cruise. The data show that all phytoplankton populations preferentially utilize nitrate (≥55%) across the Indian Sector of the Subantarctic, potentially driving higher C export potential than previously estimated. Indeed, near the Subantarctic islands, 72% of microand >80% of nano- and picophytoplankton growth is supported by nitrate. This is likely due to the partial alleviation of phytoplankton iron and silicate stress, largely as a result of bathymetric upwelling, which constitutes a manifestation of the island mass effect. C export potential is lower in the open ocean region away from the islands where iron stress has been shown to be higher; here, nitrate supports >55% of micro- and picophytoplankton and 7 to 79% of nanophytoplankton growth. In terms of relative abundance (RA), the open Subantarctic is dominated by picoeukaryotes (64%), although there exists a large disconnect between relative abundance and potential contribution to C export. The three largest surface-ocean phytoplankton populations included in this study – microphytoplankton, cryptophytes, and nanoeukaryotes – each contribute ~30% to the total C export potential across the Subantarctic Indian sector while picophytoplankton contribute ~5%. Thus, as has been concluded previously, the larger phytoplankton size classes are disproportionately important drivers of the Subantarctic biological pump. Other interesting ecological findings include diatom-dominated microphytoplankton populations apparently fueled by a significant fraction of regenerated N, even in areas of iron supply, and Synechococcus relying near-exclusively on new N, in contrast to subtropical observations. Additionally, the abundance of Synechococcus appears to be controlled by the availability of iron across the Subantarctic, with silicate and temperature playing a supporting role.
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Kottmeier, Dorothee Marie [Verfasser], Björn [Akademischer Betreuer] Rost, Björn [Akademischer Betreuer] Rost, and Anya [Akademischer Betreuer] Waite. "Process understanding of photosynthetic fluxes underlying ocean acidification responses in the coccolithophore Emiliania huxleyi / Dorothee Marie Kottmeier. Betreuer: Björn Rost. Gutachter: Björn. Rost ; Anya Waite." Bremen : Staats- und Universitätsbibliothek Bremen, 2015. http://d-nb.info/1096391163/34.
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Lemkau, Karin Lydia. "Comprehensive study of a heavy fuel oil spill : modeling and analytical approaches to understanding environmental weathering." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77784.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>Driven by increasingly heavy oil reserves and more efficient refining technologies, use of heavy fuel oils for power generation is rising. Unlike other refined products and crude oils, a large portion of these heavy oils is undetectable using the traditional gas chromatography-based techniques on which oil spill science has been based. In the current study, samples collected after the 2007 M/V Cosco Busan heavy fuel oil spill (San Francisco, CA) were analyzed using gas chromatography (GC)-based techniques, numerical modeling and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to examine natural weathering of the oil over a one and a half year period. Traditional GC techniques detected variable evidence of evaporation/ dissolution, biodegradation and photodegradation. Petroleum hydrocarbon compounds smaller than -n-C 16 were rapidly lost due to evaporation and dissolution. Significant biodegradation was not detected until one month post spill while photodegradation was only observed at one field site. To further examine the processes of evaporation and dissolution, samples were analyzed with comprehensive two-dimensional GC (GCxGC) and a physiochemical model developed to approximate quantitative apportionment of compounds lost to the atmosphere and water. Model results suggest temperature is the primary control of evaporation. Finally, to examine the prominent non-GC amenable component of the oil, samples were analyzed with FT-ICR MS. Results showed expected clustering of samples, with those samples collected sooner after the spill having the most compositional similarity to the unweathered oil. Analysis of dominant heteroatom classes within the oil showed losses of high molecular weight species and the formation of stable core structures with time. These results highlight the susceptibility to weathering of these higher molecular weight components, previously believed to be recalcitrant in the environment. Research findings indicate that environmental weathering results in removal or alteration of larger alkylated compounds as well as loss of lower molecular weight species through evaporation/dissolution, biodegradation and photodegradation, with a resultant fraction of stable compounds likely to remain in the environment years after the spill. This research demonstrates the advantages of combining multiple analytical and modeling approaches for a fuller understanding of oil spill chemistry.<br>by Karin Lydia Lemkau.<br>Ph.D.
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Vogel, Nikolas [Verfasser], Christian [Akademischer Betreuer] Wild, and Kai [Akademischer Betreuer] Bischof. "Understanding individual and combined effects of ocean acidification, warming and coastal runoff on marine calcifying organisms on tropical coral reefs / Nikolas Vogel. Gutachter: Christian Wild ; Kai Bischof. Betreuer: Christian Wild." Bremen : Staats- und Universitätsbibliothek Bremen, 2015. http://d-nb.info/1072303817/34.
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Millan-Otoya, Juan Carlos. "Understanding Climate Change and Sea Level: A Case Study of Middle School Student Comprehension and An Evaluation of Tide Gauges off the Panama Canal in the Pacific Ocean and Caribbean Sea." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5995.
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The present study had two main objectives. The first was to determine the degree of understanding of climate change, sea level and sea level rise among middle school students. Combining open-ended questions with likert-scaled questions, we identified student conceptions on these topics in 86 students from 7th and 8th grades during 2012 and 2013 before and after implementing a Curriculum Unit (CU). Additional information was obtained by adding drawings to the open-ended questions during the second year to gauge how student conceptions varied from a verbal and a visual perspective. Misconceptions were identified both pre- and post-CU among all the topics taught. Students commonly used climate and climate change as synonyms, sea level was often defined as water depth, and several students failed to understand the complexities that determine changes in sea level due to wind, tides, and changes in sea surface temperature. In general, 8th grade students demonstrated a better understanding of these topics, as reflected in fewer apparent misconceptions after the CU. No previous study had reported such improvement. This showed the value of implementing short lessons. Using Piaget’s theories on cognitive development, the differences between 7th and 8th grade students reflect a transition to a more mature level which allowed students to comprehend more complex concepts that included multiple variables.
The second objective was to determine if the frequency of sea level maxima not associated with tides over the last 100 years increased in two tide gauges located on the two extremes of the Panama canal, i.e. Balboa in the Pacific Ocean and Cristobal in the Caribbean Sea. These records were compared to time series of regional sea surface temperature, wind speed, atmospheric pressure, and El Niño-Southern Oscillation (ENSO), to determine if these played a role as physical drivers of sea level at either location. Neither record showed an increase in the frequency of sea level maxima events. No parameter analyzed explained variability in sea level maxima in Cristobal. There was a significant correlation between the zonal component of the wind and sea level at Balboa for the early record (r=0.153; p-value0.05). There was a clear relationship between sea level maxima and ENSO. 70% of the years with higher counts of higher sea level events corresponded to El Niño years. A randomization test with 1000 iterations, shuffling the El Niño years, showed most of these randomizations grouped between 14-35% of the events occurring during a randomized El Niño year. In no iteration did the percentage of events that occurred during El Niño years rise above 65%. The correlation with zonal wind and the probable correlation with sea surface temperature can be linked via ENSO, since ENSO is associated with changes in the strength of the Trade Winds and positive anomalies in the sea surface temperature of the tropical Pacific Ocean.
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Sathyanarayanan, Anju [Verfasser]. "Understanding projected salinity changes in the global ocean of the MPI-Earth system model under a global warming scenario : Verständnis der projizierten Salzgehaltsänderungen im globalen Ozean des MPI-Erde-Systemmodells unter einem Szenario der globalen Erwärmung / Anju Sathyanarayanan." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1221276417/34.
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Grandquist, Joshua Ryan. "Progressing the understandings of sea spray aerosol through model systems and nem Methods of analysis." Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1845.
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Currently, there exists a great deal of uncertainty regarding atmospheric aerosols and the role that they play within the Earth’s atmosphere. It is known that atmospheric aerosols can play a role in the Earth’s climate by scattering and absorbing solar radiation or acting as a cloud condensation nuclei. The purpose of this work is to obtain an improved understanding of the chemistry of atmospheric aerosols to better determine their impacts the environment, air quality, and climate.
This work revolves around one specific type of atmospheric aerosol, i.e. sea spray aerosol. Sea spray aerosol is generated via breaking waves, through wind-driven mechanisms. Ocean water covers roughly 71% of the Earth’s surface, and from this over 1300 Tg of sea spray aerosols is emitted into the atmosphere every year. However, until recently, the study of sea spray was very challenging and often inconclusive due to the inability to filter background particles out. In this work, the understanding of sea spray aerosol is progressed by taking a two-pronged approach. First, this work focuses on the study of model systems of simple ocean surfactants and NaCl and the change in chemistry that occurs when the two are in the presence of each other. Second, sea spray samples generated during a biological bloom are isolated and analyzed. Using this two pronged approach, it is shown that model systems can provide supporting evidence for hypotheses created from trends discovered in more complex samples. Finally, common aerosol generation, storage, and analysis techniques are studied in order to improve our understanding of their effects on aerosol particles.
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Font, Yvonne. "Contribution to the understanding of the westernmost Ryukyu subduction termination into the active arc-continent collision of Taiwan : new insights from seismic reflection analyses and earthquake relocation /." Montpellier : Institut des sciences de la terre, de l'eau et de l'espace de Montpellier, Université Montpellier II, 2002. http://catalogue.bnf.fr/ark:/12148/cb388580077.
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Th. doct.--Sci. de la terre et de l'eau--Montpellier 2, 2001.<br>Mention parallèle de titre ou de responsabilité : [@Contribution à l'étude de la terminaison ouest de la subduction des Ryukyus au niveau de la collision active arc-continent à Taiwan] : apports de la sismique réflexion et de la relocalisation hypocentrale. Bibliogr. p. 271-279. Résumés en français et en anglais.
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Woods, BL. "Understanding the energy pathways through Southern Ocean mesopelagic communities." Thesis, 2022. https://eprints.utas.edu.au/47527/.
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Mesopelagic fishes and squids play critical roles in mediating the transfer of energy through Southern Ocean pelagic food webs. However, the energy pathways comprised of mesopelagic fishes and squids remain understudied compared to those mediated by Antarctic krill Euphausia superba. In part, this has been due to the difficulty of sampling and observing taxa in the remote and harsh environment of Southern Ocean pelagic ecosystems. This has limited our understanding of mesopelagic fish and squid functional roles and baselines of community structure and function. Increasingly, evidence suggests that environmental change is likely to have effects on mesopelagic communities that may result in shifting food web dynamics. It is therefore essential to establish baseline understanding of the structure and function of mesopelagic groups to predict and assess the magnitude of future change.
This thesis examined the poorly studied trophic pathways mediated by mesopelagic fishes and squids across regional and circumpolar spatial scales. Specifically, biochemical tracer techniques were used to obtain new empirical knowledge of fish and squid functional roles and key food web linkages in the Southern Ocean. Additionally, I integrated survey data of mesopelagic fishes from seven national Antarctic research programs into a comprehensive circumpolar dataset. An ensemble modelling approach was then used to investigate key determinants of mesopelagic fish abundance and distribution, highlighting important geographic areas of mesopelagic fish occurrence.
Chapter 2 investigated the trophic role of mesopelagic fishes in the region of the southern Kerguelen Plateau in the Indian sector of the Southern Ocean and the role of body size on the trophic structure of the community. I used bulk carbon and nitrogen stable isotopes to quantify species’ isotopic niches and to examine the relationship between body size and trophic position. I found high overlap in the trophic niches among species although evidence indicated latitudinal variation in the trophic position estimates of taxa, broadly partitioned by the southern Antarctic Circumpolar Current Front; and a size-based trophic structure between species.
Chapter 3 provided the first cross-basin comparison of the trophodynamics of pelagic squids across two major oceanic sectors in the Southern Ocean (West Pacific and Indian sectors) using archived squid beaks collected from predator stomachs. I combined bulk nitrogen stable isotopes and compound specific stable isotopes to investigate the trophic role of species within each community and to assess body size relationships at the species, community, and ocean basin levels. This revealed similar trophic structuring between both locations characterised by almost three trophic levels, from mid-trophic levels to higher predators. Further, body size was not a strong determinant of trophic structure in either community suggesting that feeding mode and/or prey availability may be stronger determinants of trophic position.
Chapter 4 presents Myctobase, a circumpolar database of mesopelagic fishes from survey data. Here, I carried out the important step of integrating and standardizing published and unpublished survey data on the abundance, biomass, biodiversity, and methodological metadata for mesopelagic fishes of the Southern Ocean. Myctobase will enhance research capacity by providing the broadscale spatiotemporal perspective and baseline data necessary for international effort toward observing and modelling mesopelagic fish.
Chapter 5 showcases the utility of Myctobase by presenting important information on the key determinants of mesopelagic fish abundance. I used data from Myctobase to develop speciesspecific models of the abundance of eight key myctophid species and the genus Bathylagus. I used a set of environmental variables, previously correlated to myctophid occurrence records, to develop boosted regression tree models for each species. I then used these models to obtain a circumpolar prediction of abundance for each species. I found that abundance is predicted by meso- and sub-mesoscale oceanographic features, in particular the Polar Front was a major delimiting feature for the distribution of species. Furthermore, the interactions between depth and solar position were key predictors of abundance indicating diel vertical migratory behaviours in some species.
Overall, this thesis presents novel insights into the functional roles of mesopelagic fish and squid taxa and key determinants of mesopelagic fish abundance and distribution. Importantly, this thesis takes fundamental steps towards the development of baselines of community structure and function and the broadscale spatiotemporal perspective necessary for the holistic management and conservation of open-ocean pelagic ecosystems in the Southern Ocean.
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Matear, Richard J. "Understanding the CO₂cycle in the North Pacific Ocean using inverse box models." Thesis, 1993. http://hdl.handle.net/2429/1812.
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Tracer transports across 35°N were computed using the hydrographic data from a synoptic section (INDOPAC) and from the Levitus annual mean section. The tracer transports calculated from the INDOPAC section were better able to close the tracer budgets in the North Pacific than the Levitus section. The transport calculations showed that highly resolved hydrographic data are necessary to accurately determine the tracer transports, and pointed out the sensitivity of the calculation to errors in the Ekman transports and air-sea exchanges of fresh water. The inverse box model was applied to data generated from the Hamburg LSGOC-biogeochemical model. For this data, the mixing transports of the tracers were important for closing the tracer budgets. Applying the inverse box model to the temperature, salinity, total CO2, alkalinity, phosphate, oxygen, POC, calcite, and 14C fields produced poor results. With the addition of velocity shear information, the inverse box model extracted the correct velocity fields and produced air-sea exchanges and detrital rain rates consistent with the known values from the Hamburg model. A model of the nutrient and carbon cycles in the North Pacific north of 24°N is formulated, and water flow rates, eddy mixing coefficients, particle fluxes and air-sea exchange rates of fresh water, heat, CO2 and 02 are calculated. The model incorporates geostrophy, wind-driven Ekman transports and budget equations for a suite of seven tracers. Geostrophic transports are based on two highly resolved synoptic sections across the North Pacific at 24°N (Roemmich et al., 1991) and 47°N (Talley et al., 1991). Tracer distributions are obtained from historical station data. Budgets of mass, heat, salt, oxygen, phosphate, silicate, CO2 and alkalinity are satisfied simultaneously in the North Pacific. The water transports in the model are in agreement with other transport calculations for the Pacific. The calculated heat transport showed that the subtropical North Pacific transfers heat into the atmosphere while the subarctic ocean gains heat. The net heat lost by the North Pacific ocean was 0.12 ± 0.08 PW. The North Pacific Ocean was calculated to be a sink of 0.1 ± 0.1 Gt C yr-1 of atmospheric carbon. The calculated maximum values of new production for the subarctic and subtropical regions are 42 g C m-2 yr-1 and 12 g C m-2 yr-1respectively. The influence of the dissolved organic matter on the nutrient and carbon cycles is investigated using the data reported by Suzuki et al., (1985). The model showed that the dissolved organic matter had little influence on the carbon and nutrient cycles. More data for the dissolved organic matter should be collected to verify this result.
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Ansorge, I. J., P. W. Froneman, J. R. E. Lutjeharms, et al. "An interdisciplinary cruise dedicated to understanding ocean eddies upstream of the Prince Edward Islands." 2004. http://eprints.ru.ac.za/344/1/sajs_froneman_an_interdisc_cruise.pdf.
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A detailed hydrographic and biological survey was carried out in the region of the South-West Indian Ridge during April 2004. Altimetry and hydrographic data have identified this region as an area of high flow variability. Hydrographic data revealed that here the Subantarctic Polar Front (SAF) and Antarctic Polar Front (APF) converge to form a highly intense frontal system. Water masses identified during the survey showed a distinct separation in properties between the northwestern and southeastern corners. In the north-west, water masses were distinctly Subantarctic (>8.5°C, salinity >34.2), suggesting that the SAF lay extremely far to the south. In the southeast corner water masses were typical of the Antarctic zone, showing a distinct subsurface temperature minimum of <2.5°C. Total integrated chl-a concentration during the survey ranged from 4.15 to 22.81 mg chl-a m[superscript (-2)], with the highest concentrations recorded at stations occupied in the frontal region. These data suggest that the region of the South-West Indian Ridge represents not only an area of elevated biological activity but also acts as a strong biogeographic barrier to the spatial distribution of zooplankton.
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Chan, Neil Ching Siang. "Effect of ocean acidification on reef-building corals: understanding variability and projecting population-level impacts." Thesis, 2015. https://researchonline.jcu.edu.au/46527/1/46527-chan-2015-thesis.pdf.
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Understanding the long-term ecosystem level impacts of ocean acidification on marine environments is critical to informing national and international policies on carbon emission targets. However, key to understanding such long-term impacts is the ability of projection models to scale up short-term physiological responses to long-term ecosystem-level impacts. This thesis aims to improve upon previous models projecting the impacts of ocean acidification on coral reefs by incorporating the effects of ocean acidification on every stage of the coral life cycle, and also by deepening our understanding of how flow potentially influences the effects of ocean acidification on calcification.
Experimental studies investigating the effects of ocean acidification on calcification have produced a wide range of responses. However, as yet there have been no attempts to produce a summary response that can be used in projection models. Thus in Chapter 2, I use regression-based meta-analysis to produce a quantitative summary of the effect of ocean acidification on calcification from all existing experimental studies. I also test several factors that may explain significant amounts of variability in experimental results so far. The effect of ocean acidification on calcification was found to be less sensitive than originally thought, ~15% per unit change in aragonite saturation state (Ω(Arag)). I also found that studies employing buoyant weighting found significantly smaller decreases in calcification per unit Ω(Arag) (~10%), compared to studies using the alkalinity anomaly technique (~25%).
Despite recent studies suggesting that coral recruitment (when including the effects on crustose coralline algae) is very sensitive to ocean acidification, projection models to date have yet to take into account the effects of ocean acidification on pre- and post-settlement stages of corals. In Chapter 3, I used the quantitative summary from Chapter 2, combined with a similar meta-analysis of recruitment, in an integral projection model to evaluate the effects of ocean acidification on growth and recruitment on long-term population growth. I found that the effects of ocean acidification on recruitment potentially exert more influence on long-term population growth rate than the effects of ocean acidification on growth, although there is substantial uncertainty associated with recruitment-mediated effects, due to the comparative paucity of studies of effects of ocean acidification on this aspect of the life cycle.
The meta-analysis of the effects of ocean acidification on calcification also revealed that among-study variation is large. It had been suggested that interactions between ocean acidification and other factors might account for a proportion of the variability between experimental results. One potential interacting factor that has not received any attention is flow, despite its long recognized role in shaping reefs through its influence on mass-transfer rates. In Chapter 4, I show, using flume experiments, that flow, through its effects on photosynthesis, mediates the effect of ocean acidification on calcification of Acropora secale. The interactive effect is large, with the sensitivity of calcification to decreasing Ω(Arag) increasing by ~0.5% per cms⁻¹ increase in flow. To elucidate the mechanisms behind the flow-ocean acidification interaction, I then use an experimental micro-sensor study to parameterize a basic diffusion-reaction-uptake model (Chapter 5). The model predicted tissue surface pH well and showed that low flow, through thickening of the diffusive boundary layer, increases tissue surface pH. However, these elevations in tissue surface pH have been found at relatively low flows that are rarely encountered by corals in nature, suggesting that the DBL effect is unlikely to ameliorate the decreases in coral calcification under ocean acidification.
The overarching aim of my thesis was to improve upon previous models projecting the impacts of ocean acidification on coral reefs. This is achieved both by incorporating the effects of ocean acidification (from all existing experimental studies) on every stage of the coral life cycle into projections, and also by deepening our understanding of an important interactive factor (flow) that is driving variability in sensitivity of calcification to ocean acidification. In a broader context, this thesis provides a template for quantitatively summarizing existing knowledge of how demographic rates change in response to a stressor, and a modelling framework that can be used to assess the impacts those changes on population growth and stability.
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Banavage, Meg Elise. "Phenomenology in a wetsuit : understanding biophilia in pacific coastal environments." 2013. http://hdl.handle.net/10170/590.
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To examine possible links between biophilia (love for living systems) and outdoor adventure training, this study explored various emotional relationships participants developed during Hooksum Outdoor School on Vancouver Island, British Columbia. Drawing from phenomenological psychology, ecopsychology, outdoor adventure training, and biophilia literature, I sought to answer the questions (1) if, and how, individuals develop emotional relationships with coastal environments; (2) what role the ocean plays in emotional change; (3) how individuals act in response to their relationships with the coast. Analysis included grouping themes from observation notes, questionnaires, and Interpretative Phenomenological Analysis of individual interviews. A focus was bringing the researcher into participants' lifeworlds as they experienced the program. Four individual participant stories demonstrate active relationship-building (1) within participants' inner selves; (2) between each other; (3) with the coastal environment. Findings contribute to recommendations for future research, providing insight into how program design can effectively address the biophilia tendency.
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Beaudoin, Simon. "Understanding the emergence of norms in world politics : the case of plastic pollution in the world ocean." Thesis, 2020. http://hdl.handle.net/1866/25044.
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This research provides a novel outlook on the emergence of norms in world politics. Guided by a constructivist theoretical framework and a process tracing methodology, it tests Martha Finnemore and Kathryn Sikkink's pioneering life cycle model of norms (1998) with an unexplored case study. By investigating the processes that led to the legally binding Plastic Waste Amendments of the Basel Convention, it evaluates the model’s main mechanisms and studies the question of ‘How can we explain the emergence of a norm on plastic pollution within the scope of the Basel Convention?’ To do so, it combines an in-depth analysis of the international relations literature, official reports, and carefully selected interviews with actors involved in the global governance of plastic and the World Ocean. This research shows that co-construction processes between ideas, agents, and structures are at play in the emergence of norms. It offers a detailed understanding of the processes of norm emergence in world politics, original insights for the global governance of plastic pollution in the World Ocean, and opportunities to answer the challenges brought by transnational environmental issues. The findings of this research will likely be of particular interest for global environmental governance scholars and to those looking for pathways to foster global cooperation.<br>Cette recherche offre une perspective nouvelle sur l’émergence des normes en politique mondiale. Guidé par un cadre théorique constructiviste et une méthodologie basée sur le traçage des processus, elle teste le modèle de cycle de vie des normes de Martha Finnemore et Kathryn Sikkink (1998) par l’entremise d’une étude de cas inexplorée. En étudiant les processus qui ont menés aux amendements juridiquement contraignants sur les déchets de plastique de la Convention de Bâle, elle évalue les principaux mécanismes du modèle de cycle de vie des normes et étudie la question suivante : « Comment expliquer l’émergence d’une norme sur la pollution des plastiques dans le cadre de la Convention de Bâle ? ». Pour ce faire, cette étude combine une analyse approfondie de la littérature des relations internationales, des rapports officiels et des entretiens soigneusement sélectionnés avec des acteurs œuvrant dans la gouvernance globale du plastique et de l'océan mondial. Cette recherche montre que des processus de co-construction entre idées, agents et structures contribuent à l'émergence des normes. Cette recherche offre une compréhension détaillée des processus d'émergence des normes en politique mondiale; des perspectives originales pour la gouvernance globale de la pollution plastique dans l'océan mondial; et des opportunités pour relever les défis posés par les enjeux environnementaux transnationaux. Les résultats de cette recherche seront probablement d’intérêt pour les spécialistes de la gouvernance environnementale globale et pour ceux qui cherchent des moyens pour renforcir la coopération mondiale.
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Higginson, Simon. "Mapping and understanding the mean surface circulation of the North Atlantic: Insights from new geodetic and oceanographic measurements." 2012. http://hdl.handle.net/10222/14866.
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The mean dynamic topography (MDT) of the ocean is closely related to the mean surface
circulation. The objective of this thesis is to produce estimates of the MDT for the North
Atlantic using newly available data from ocean and gravity observing systems, to evaluate
these new estimates and so improve our understanding of the circulation.
Oceanographic estimates of the MDT are based on the mean temperature and salinity
(TS) fields of the ocean. These are typically averages from sparse observations collected
over many decades. The ocean is a non-stationary system so it is more appropriate to define
the mean for shorter, specific periods. Whilst the Argo observing system has increased the
frequency and resolution of in situ oceanographic measurements, high frequency (eddy)
variability remains. A new technique is described for removing this variability using
satellite altimeter measurements of the sea surface height. A new TS mean is produced,
relating to the period from 2000 to 2007, and this is used to map a new oceanographic
estimate of the MDT using an ocean circulation model.
New geodetic estimates of the MDT are produced using geoid models that incorporate
gravity measurements from the ongoing GRACE and GOCE satellite missions. These
are compared with the new oceanographic estimate and validated against independent
observations such as drifter speeds. The geodetic method produces realistic estimates of
the mean surface circulation, thereby realizing the long time dream of oceanographers to
observe the ocean circulation from space. The new oceanographic estimates are not as
accurate, but the new TS mean contributes to improvements in the performance of ocean
models, a necessary step in understanding and predicting the oceans.
Coastal tide gauges can provide an accurate estimate of the alongshore tilt of the coastal
MDT and this has been used to evaluate the above estimates. Temporal variability of the tilt
along the coast of the South Atlantic Bight is used, with statistical methods and an ocean
circulation model, to identify the processes contributing to the tilt. A new opportunity to
use tide gauges as part of an observing system for the ocean circulation is discussed.
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Johnson, SC. "The geochemistry of metalliferous black shales : understanding primary enrichments, metamorphic processes, and the role of metal-rich black shales in archiving earth evolution." Thesis, 2017. https://eprints.utas.edu.au/23853/1/Johnson_whole_thesis.pdf.
Full textAbstract:
Black shales offer an important context to study the evolution of the oceans and atmosphere. As an archive of past climatic, evolutionary and geodynamic events in Earth history they offer the opportunity to further understand the nature of such events. Various redox sensitive and bio-essential trace metals can become enriched in black shales as a function of the nature of the environment in which they were deposited. Of particular interest are shales with high metal enrichment, as they may represent an important geochemical flux. In addition to archiving paleo-ocean and climatic conditions, metal-rich black shales offer important economic targets for hydrocarbon and mineral exploration. Previous work has shown that many important trace metals in black shales are hosted by diagenetic pyrite. Furthermore, metal-rich pyrite has been argued as a potential source for orogenic gold deposits where the metamorphic breakdown of pyrite to pyrrhotite releases gold and other trace metals.
This thesis presents a series of studies on aspects of black shale enrichment and mineralogy and offers greater insight as to the evolution of our oceans and atmosphere and how this may relate to secular metal enrichments. Each adopts a multi-proxy, geochemical approach, augmenting pyrite trace element chemistry with isotopic, and whole-rock geochemical or mineralogical data. In addition to addressing the nature of the depositional environment of black shales, mechanisms of ore genesis via the metamorphism of metal-rich shale sequences are also presented and evaluated. Four main aspects of the geochemistry of black shales are investigated in this thesis: 1) primary metal enrichment as a result of the changing nature of the water column during climatic perturbation, 2) the application of pyrite trace element chemistry along with other geochemical techniques to understand, and differentiate, primary metal enrichments and metamorphic overprint, 3) mechanisms by which pyrite may convert to pyrrhotite in black shale and what implications this may have for metal mobility, and 4) understanding of metal enrichments in black shale through geological time in the context of geodynamic and geochemical evolution.
The understanding of primary metal enrichments in black shales is critical in order to interpret the nature of the depositional environment. Chapters 2, 3 and 4 offer reviews of metal enrichment in sediments through time, as well as whole rock and pyrite trace element chemistry, as a means to record the chemical nature of the water column at the time of deposition. This is then applied in Chapter 5 to a metalliferous black shale section in NW Estonia of Cambrian to Ordovician age. This work contains a new detailed sedimentological study of the section to establish a depositional context. This is augmented by a high-resolution multi-proxy data and isotope geochemistry suggests that the section archives a major carbon isotope excursion (the Steptoean Positive Isotope Excursion; SPICE), not previously reported in these rocks, and allows the section to be placed in a global context. The high phosphorous content of the biograinstones deposited prior to the carbon isotope excursion suggests that phosphogenesis may have led to increased bio-productivity, affecting the carbon cycle. The high pyrite content and the geochemistry of this mineral in the lower portion of the black shale, which sits above the isotope excursion, suggests that the SPICE event may have led to the onset of low-oxygen conditions across the Baltica shallow shelf, and the deposition of metal-rich black shales.
In Chapter 6, the geodynamic and biochemical processes associated with metal enrichments in the formation metal-rich shales are reviewed and discussed together with a geochemical and mineralogical study of the Talvivaara deposit in Finland. As the world’s largest black-shale poly-metallic deposit it offers a context to evaluate the economic aspects of black shale enrichment. The Paleoproterozoic age of this deposit and the fact that there are no known analogues that match its size, suggests that there may have been unique environmental factors that played a role in its metal enrichment. Much like the Estonian example, Talvivaara was deposited in the immediate wake of a large, global carbon isotope excursion. The excursion (the Lomagundi- Jatuli event, ~2.1 Ga) is the largest carbon isotope excursion preserved in the rock record and is followed by the first, and largest, mass burial of organic carbon in Earth history. This suggests that there may be analogous processes operating, but on different scales, in order to facilitate such enrichments. The deposit has been metamorphosed to amphibolite facies with only some primary pyrite, zircon and bituminous organic matter preserved. In-situ δ\(^{34}\)S-isotopic values of the sulfide phases and LA-ICP-MS analyses of iron sulfide phases, shows that the earliest pyrite (interpreted to be of syn-sedimentary to early-diagenetic in origin) is trace metal rich. The δ\(^{34}\)S values in these pyrites suggest bacterial sulfate reduction from an open sulfate reservoir. The earliest pyrite is the most metal-rich, suggesting that the original depositional environment facilitated high metal concentrations. The shale package was then metamorphosed releasing trace elements and sulfur that then went on to form their own phases.
Chapter 7 presents new data and insights as to the nature of metamorphic reduction of pyrite to pyrrhotite in black shales. Often this transformation is only considered as proceeding at greenschist facies metamorphism (~300°C, and above). An experimental study, focusing on the magnetic character of pyrite, suggests that the transformation begins at ~177°C. The lower temperature proposed is supported by LA-ICP-MS studies of pyrite and pyrrhotite in Estonian oil shale and diagenetic to catagenetic sulfide concretions in sub-greenschist facies black shales from NW Russia. A model is presented suggesting that the degradation of organic matter during catagenesis is sufficient in producing enough reducing potential to facilitate the initial stages of the transformation to pyrrhotite.
Chapter 8 presents a synthesis of the geochemistry of metal-rich black shales. Some of the most metal-rich black shales worldwide are classified and compared to ‘normal’ black shales from throughout Earth history. In doing so, a new model is presented which suggests that during the Phanerozoic, plate collisional events led to increased detrital material into basins, leading to increased bio-productivity and atmospheric O\(_2\). With increasing O\(_2\) in the atmosphere, the processes of weathering and erosion became more vigorous leading to further influx of detritus and blooms of bio-productivity promoting the development of water column anoxia. Eventually, the cycle breaks when uptake by organisms exceeds input from the continents, leading to the return of ‘normal’ black shales and increasing carbon release to the atmosphere. This process is likely to have been the dominant process during the Phanerozoic, where supercontinent cycles are more dynamic and cover greater surface area. However, the Proterozoic also has some of the largest metalliferous, and organic-rich, sediments in the rock record and do not directly correlate to periods of supercontinent amalgamation. Instead, a discussion is presented that addresses the influence of widespread glaciations as a process to effectively erode, whilst simultaneously release oxygen, leading to increased oxidative weather and bio-productivity in their aftermath.
46
Bedford, M. "Prey-field use by top predators of the Southern Ocean: understanding foraging dynamics of macaroni penguin (Eudyptes chrysolophus) near Heard Island." Thesis, 2013. https://eprints.utas.edu.au/22465/1/Bedford_2013_Thesis.pdf.
Full textAbstract:
This study used data collected during the 2003/04 Heard Island Predator Prey Investigation and Ecosystem Study (HIPPIES project). It is the first study to directly compare diet, foraging, and prey-field dynamics with energetics of macaroni penguins (Eudyptes chrysolophus) around Heard Island.
Diet and foraging dynamics were evaluated for the guard and crèche stages of breeding macaroni penguins from Heard Island. Diet changed significantly between the two stages (p < 0.005), from a diet dominated by krill (83%) in the guard stage, to a more variable diet in the crèche stage (43% krill, 33% fish, 23% amphipods). The observed change in diet corresponded with a change in foraging behaviour. During the guard stage foraging trips were short (mean = 109.1 km ± se 7.2 km), but became significantly (p < 0.005) longer (mean = 660 km ± 139.2 km) in the crèche stage.
These changes lead to interesting questions regarding the relationship between diet, foraging and prey-field dynamics. The prey-field of macaroni penguins was sampled with nets and acoustic techniques, and showed that krill is available both close to the island and offshore. In contrast, fish are more abundant over deeper waters offshore. The observation that penguins choose to forage further offshore, where fish are more abundant (but the availability of krill is unchanged) suggests that macaroni penguins may prefer fish to krill.
This theory was analysed by examining energy contents of prey species, and energetic requirements of breeding penguins. Energetically, fish found in the stomach samples of the macaroni penguins have a higher value than krill (8.42 kJ/g and 5.05 kJ/g respectively). This suggests that when macaroni penguins at Heard Island are limited in the distances they can forage in the guard stage, they settle for lower-energy krill as their main food source. However, in the crèche stage when they are able to forage further, they preferentially feed on food with higher energy content.
By extrapolating from the energy and food requirement budgets for one breeding pair, the prey consumed for the entire study colony at Heard Island was estimated. This suggested another possibility for the observed changes between the two breeding stages; that of prey depletion. This appears to be a real possibility around the island, particularly when looking at the large number of land-based predator populations on Heard Island. Further analysis of predator diets, better estimates of available prey biomass, and species-specific energy budgets are required to confirm this suggestion.
47
Huang, Boyin. "Understanding the temperature trends in the upper-oceans." 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.
Full text
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Pożoga, Karolina. "Diagnozowanie i ocena logopedyczna przebiegu afazji w ostrej fazie niedokrwiennego udaru mózgu." Doctoral thesis, 2017. https://depotuw.ceon.pl/handle/item/2568.
Full textAbstract:
Temat prezentowanej pracy dotyczy przebiegu afazji w ostrej fazie niedokrwiennego
udaru mózgu – wiąże się z ogólnym pytaniem o dynamikę objawów afatycznych
w tzw. ostrym okresie zachorowania, o ich ustępowanie, utrzymywanie bądź nasilanie się
oraz związek z procesem zdrowienia po udarze mózgu, a także o czynniki mogące
determinować obraz afazji w ostrym stadium udaru mózgu. Kwestie te są ważne zarówno
z punktu widzenia badacza, jak i praktyka. Stanowią istotny problem w aspekcie
diagnostycznym i terapeutycznym.
Pacjenci objęci badaniem stanowili grupę 120 osób, u których po raz pierwszy w życiu
wystąpił udar niedokrwienny mózgu. Wszyscy hospitalizowani byli na Oddziale Neurologii
z Pododdziałem Udarowym Powiatowego Zakładu Opieki Zdrowotnej w Starachowicach.
Badania przeprowadzone zostały z wykorzystaniem testu FAST (Frenchay Aphasia Screening
Test). Jest to test przesiewowy, dzięki któremu stwierdzić można obecność cech afazji.
Ocena za pomocą testu FAST przeprowadzona została dwukrotnie: pierwszy raz w 2., a drugi
raz w 9. dobie pobytu pacjenta na oddziale. W badaniach oceniano dynamikę objawów afazji
w czterech obszarach zgodnie z zawartością testu: rozumienie mowy, mowa ekspresyjna,
czytanie i pisanie. Prowadzono obserwacje ukierunkowane na ustępowanie, utrzymywanie
bądź nasilanie objawów afazji oraz związek tego stanu rzeczy z procesem zdrowienia
po udarze mózgu. Analogicznie (również dwukrotnie w 2. i 9. dobie) pacjenci włączeni
do badań poddawani byli ocenie z wykorzystaniem skali NIHSS (National Institutes of Health
Stroke Scale) dokonywanej przez lekarzy. Skala ta ocenia stopień ciężkości udaru mózgu.
W odniesieniu do współczesnych teorii prezentowanych w literaturze polskiej
i zagranicznej, a także na podstawie prowadzonych badań i obserwacji własnych, przyjęto
założenie, że afazja w ostrej fazie udaru mózgu ma charakter zmienny, a jej objawy cechuje
niestabilność. Przyjęto więc hipotezę, że u pacjentów z rozpoznaną afazją w ostrej fazie udaru
mózgu zaburzenia mają charakter dynamiczny.
Do celów głównych pracy należała ocena przebiegu afazji w ostrej fazie udaru mózgu
–w warunkach leczenia szpitalnego z wykorzystaniem testu FAST, a także ocena rzetelności
testu FAST i jego przydatności w diagnozowaniu i monitorowaniu przebiegu afazji w ostrej
fazie udaru mózgu, jak również próba wskazania zalet oraz ograniczeń tego narzędzia
badawczego w zastosowaniu w ostrym stadium udaru. Celem pracy uczyniono również
analizę czynników, które mogą mieć wpływ na zachodzące zmiany w obrazie afatycznych
zaburzeń mowy w ostrej fazie udaru.
Wyniki badań własnych pozytywnie weryfikują przyjętą hipotezę dotyczącą
zmienności przebiegu afazji w ostrej fazie udaru mózgu. Analizując wyniki poszczególnych prób testu FAST, wyraźnie widać różnice w ich wykonaniu pomiędzy pierwszym a drugim
pomiarem. Zmienia się zarówno obraz afazji, jak i obraz kliniczny pacjenta, na co wskazują
zachodzące różnice w skali NIHSS pomiędzy pierwszym a drugim pomiarem.
Poprzez analizę ilościową i jakościową zebranego materiału badawczego
oraz na podstawie prezentacji wyników analiz w formie zbiorczych tabel, a także w postaci
graficznej i dzięki zastosowanym opisom, można zgodnie z przyjętą procedurą badawczą oraz
wedle zastosowanych narzędzi badawczych obserwować u badanych pacjentów przebieg
afazji, a także przebieg samego udaru.
W niniejszej pracy podjęto także próbę oceny wpływu takich czynników, jak: wiek,
wykształcenie, płeć na przebieg afazji i przebieg ogólnego zdrowienia w udarze. Potrzeba
w tym zakresie dalszych badań – zarówno ilościowych, jak i jakościowych –
uwzględniających te i inne czynniki jako potencjalne predykatory determinujące obraz afazji
i udaru.
Jak obrazują wyniki badań, test FAST stosowany jest z powodzeniem w ostrej fazie
udaru mózgu dzięki prostocie swojej konstrukcji i łatwości użycia. Zastosowanie testu FAST
i skali NIHSS umożliwia wykazanie ilościowych zmian, pozwala na uchwycenie przebiegu
afazji i przebiegu samego udaru oraz stanowi czytelne udokumentowanie tego procesu.
Takie oddziaływania diagnostyczne, świadomie i celowo podejmowane, a także właściwie
zorganizowane w krótkim czasie pobytu na oddziale leczenia udaru mózgu, wspomagają
wybór strategii oddziaływań terapeutycznych, zwiększając szansę chorego na odzyskanie
utraconych funkcji. Stanowią rodzaj pierwszych interwencji logopedycznych i stymulację
pacjenta do podejmowania współpracy zadaniowej.
Afazja w ostrej fazie udaru ewoluuje. Wyniki badań jednoznacznie pokazują,
że nie można poprzestać na jednorazowej ocenie pacjenta w ostrej fazie udaru mózgu,
ponieważ występująca dynamika objawów weryfikuje i często zmienia diagnozę wyjściową.
W świetle wyników badań obligatoryjne wydaje się przyjęcie założenia o konieczności
przeprowadzenia przynajmniej dwukrotnej weryfikacji oceny logopedycznej pacjentów
z afazją w ostrej fazie zachorowania udarowego. Praktyka taka pomaga obserwować objawy,
ułatwia ich różnicowanie, a w konsekwencji może prowadzić do rozstrzygnięć
diagnostycznych. W fazie ostrej nigdy nie wystarczy jednorazowe badanie logopedyczne
pacjenta, by wiarygodnie opisać jego zaburzenia oraz stopień ich nasilenia.
Można stwierdzić, że w przypadku oceny afatycznych zaburzeń mowy w ostrej fazie
zachorowania obserwacja przebiegu i kierunku zmian może być istotna w aspekcie
ich prognozowania. Wydaje się, że warto prowadzić dalsze badania w tym zakresie z wykorzystaniem
np. strategii badań podłużnych i obserwacji przebiegu afazji u badanych pacjentów
w dalszych odstępstwach czasowych po zakończeniu hospitalizacji.<br>The subject of the following work is connected with the course of aphasia in the acute
phase of ischemic stroke, which is associated with a general question about the dynamics
of aphasic symptoms in so-called acute phase of illness, regarding abatement, maintenance
or progression, and the connection with the post-stroke recovery process, as well as the
factors that may influence aphasia in acute stroke. These issues are important from the point
of view of the researcher and clinician. They are a significant problem in both diagnostic and
therapeutic aspects.
Patients included in the study group were a group of 120 people who had ischemic
stroke for the first time in their lives. All of them were hospitalized in the Neurology Ward
on the Stroke Subunit of the District Health Care Center in Starachowice. The study was
carried out using the FAST test (Frenchay Aphasia Screening Test), which is a screening test
that can identify the presence of aphasia traits. The FAST test was performed twice: the first
time on the 2nd day and the second time on the 9th day of the patient's stay in the ward.
The study examined the dynamics of aphasia symptoms in four areas according to the content
of the test: speech generation, speech understanding, reading and writing. Observations were
made aimed at relieving, maintaining or aggravating the symptoms of aphasia, and linking
this condition with post-stroke treatment. Similarly (also twice on the 2nd and 9th day)
patients included in the study were evaluated using a NIHSS scale (National Institutes
of Health Stroke Scale) performed by physicians. This scale assesses the severity of stroke.
Considering the contemporary theories presented in Polish and foreign literature
and on the basis of conducted research and individual observations, it was assumed
that aphasia in the acute phase of stroke is variable and its symptoms are instable. Therefore
a hypothesis was adopted saying that the disorder is developing dynamically in stroke patients
with diagnosed aphasia.
The research main task was the assessment of the course of acute aphasia in FASTbased
hospital treatment, as well as reliability of FAST test and its usefulness in diagnosing
and monitoring aphasia in initial stroke as well as an attempt to identify the benefits
and limitations of this research tool for acute stroke application. The purpose of the study was
also to investigate factors that may affect the onset of changes in the aphasia speech disorders
in acute stroke.
The results of individual studies validate the adopted hypothesis on the variability
of aphasia in the acute stroke. By analyzing the results of individual FAST tests, you can
clearly see differences in their performance between first and second measurements. Both the aphasia and the clinical picture of the patient change as the NIHSS varies between the first
and second measurements.
By quantitative and qualitative analysis of the collected test material and on the basis
of presented analysis results in the form of consolidated tables, graphical representation
and by descriptions used, one can observe the course of aphasia as well as stroke according
to the applied test procedure and the research tools used.
The following research study also attempts to assess the impact of factors such as age,
education, sex on the course of aphasia, and the course of general treatment in stroke.
There is a need for further quantitative and qualitative studies in this field taking into account
these and other factors as potential determinants of aphasia and stroke.
As the study results indicate, the FAST test is successfully used in acute stroke
diagnostics due to its simple design and ease of application. The use of FAST test and NIHSS
scale provides the opportunity to determine quantitative changes in order to capture the course
of aphasia and stroke itself, becoming a clear evidence of the occurring process. Such
diagnostic actions, performed in conscious and deliberate way as well as proper organization
in short-term treatment of strokes, which support the selection of a therapeutic strategy,
increase the chance of recovering lost functions of patients. They are a sort of initial speech
therapy that stimulate the patient to undertake task-based interventions.
Aphasia in the initial phase of stroke is evolving. The results of the study clearly show
that a single patient assessment in acute stroke is not enough, as the occurring symptom
dynamics verifies and often changes the initial diagnosis. The results highlight that it is
mandatory to assume that there is a need for at least double verification of the speech
functions of aphasia patients in acute stroke phase. This kind of practice helps to observe
the symptoms, facilitate their differentiation, and, consequently, can lead to diagnostic
solutions. Never in an acute phase it is sufficient enough to examine a patient only once
to reliably describe one's disorder and severity.
It can be stated that in case of evaluation of aphasic speech disorders in acute phase
of stroke, the observation of the course and direction of change may have a prognostic value.
It seems that it would be worth to conduct further research in this area using, for example,
longitudinal study strategies and aphasia patient follow-up observations after undergone
hospitalization.