Thesis (M.A.)--Georgia State University, 2008. / Title from file title page. Jeremy Diem, committee chair; Jeremy Crampton, John Allensworth, committee members. Electronic text (126 p. : col. maps) : digital, PDF file. Description based on contents viewed July 17, 2008. Includes bibliographical references (p. 110-121).

Ph.D. in Marine Environmental Science. Includes bibliographical references (145-158).

Thesis (M.A.)--Rice University, 1976. / Includes bibliographical references (leaves 71-77).

Thesis (Ph.D.) - University of St Andrews, March 2008.

Thesis (M.S.) OGI School of Science & Engineering at OHSU, June 2007. / Includes bibliographical references (leaves 136-140).

No description available.

Intertidal cohesive sediment systems are found throughout the world in areas of low hydrodynamic energy. These systems are ecologically and economically important but are under pressure from global warming, sea level rise and other anthropogenic influences. To protect and conserve these systems it is important to understand the sediment dynamics, especially the erosional properties of the sediment. The study of sediment erosion and transport is complex, encompassing biological, chemical and physical properties of the ecosystem. This thesis contributes towards this area of research, firstly in regard to the methods used to measure sediment erosion on exposed and submerged sediments and secondly with respect to assessing influences upon sediment stability through changes in the ecosystem, comprising of both the sediment environment and the macrofaunal community. Chapter 3: In partnership with Sediment Service a thorough re-evaluation of the Cohesive Strength Meter (CSM), a commercially available device used to measure surface sediment strength, was performed. New components, deployment method and calibration protocol were devised and tested. The new design was not effective, but the deployment and calibration have improved the ease of use and interpretation CSM data. Chapter 4: The study of intertidal sediment stability was conducted during the submerged period of the tidal cycle. Protocols and methods were devised or modified to sample submerged sediments with the aim to determine how sediment properties are affected by submersion and the resulting effect on sediment stability. Sediment stability increased with submersion. The existence of a fine layer of sediment on the surface, similar to the fluff layer found in submerged sediments, is given as a suggested explanation as it may be removed by the incoming tide. However, no other changes in sediment properties were detected. This may be due to flaws in the methods used in detecting fine scale changes in the sediment surface. In situ and laboratory experiments revealed contrasting effects of submersion on sediment stability with disturbance from the sampling and movement of sediment from the field to the laboratory given as an explanation for this. Chapter 5: The influence of the ecosystem engineering polychaete Arenicola marina on sediment properties was examined with an exclusion experiment. A. marina was excluded from five 20m² plots on an intertidal mudflat on the German island of Sylt. A holistic approach was used to measure the ecosystem, including a range of biotic and abiotic sediment properties as well as the macrofauna community. It was hypothesised that A. marina’s exclusion would alter the macrofaunal community and increase sediment stability. However, there was no consistent change in the macrofauna community or sediment environment with the exclusion of A. marina and subsequently no change in sediment stability. Chapter 6: The impact of bait digging for A. marina was examined with six 5m² plots dug up and A. marina removed, the plots were then monitored over a three month period. Bait digging disturbance was expected to have an impact upon the sediment environment and macrofauna community, resulting in a reduction in both sediment stability and microphytobenthic abundance. However, bait digging had minimal impact on the macrofauna community and caused no change in the sediment environment, despite the removal of a large proportion of the A. marina population. No change was recorded in the sediment stability or biomass of the microphytobenthos, indicating that with the exception of removing A. marina, bait digging of this nature was not detrimental to the sediment ecosystem. However, the consequences of larger, longer term digging operations can not be determined from this work and further studies are suggested. The study of intertidal sediment stability was progressed with advances made in methods and protocols. The work highlighted the importance of studying sediment stability as an ecosystem function through a holistic ecosystem approach rather than isolating individual variables.

Plant interactions (e.g., competition, facilitation) are critical drivers in community development and structure. The Stress Gradient Hypothesis (SGH) provides a predictive framework for how plant species interactions vary inversely across an environmental stress gradient, predicting that facilitation is stronger with increasing levels of stress. The SGH has been supported in numerous ecosystems and across a variety of stress gradients, but recent research has demonstrated contradictory results. These discrepancies have led to SGH revisions that expand its conceptual framework by incorporating additional factors, such as other stressor types and variations in species life history strategies. In this dissertation, I examine a further modification of the SGH by proposing and testing a Multiple Stress Gradient Hypothesis (MSGH) that considers how plant interactions vary along a continuous gradient of two co-occurring stressors using mangrove and salt marsh communities as a case study. In Chapter 1, I outline the predictive framework of a MSGH, by creating a series of predictions of species interactions. The components of the MSGH predict that stressors of similar types (e.g., resource and nonresource) will have similar effects and be additive. On the other hand, varying species life history strategies and life stages will lead to extremes of plant interactions. In Chapter 2, I performed a series of experiments to test the various components of the MSGH. In Chapter 3, I performed a large-scale observational study to test whether multiple co-occurring stressors altered the cumulative effects on plant interactions, and if these stressors should be grouped (e.g., resource and non-resource, abiotic and biotic, etc.) to enhance predictability. From a series of studies conducted herein, I concluded that co-occurring stressors are important factors that control complex species interactions as shown in my MSGH modeling approach. Further, future theories need to incorporate species-specific and stressor specific grouping when modeling how species interactions shape communities. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2013.

The continental shelf on the western side of the Antarctic Peninsula is a region of substantial climate and ecosystem change. The Long Term Ecological Research project at Palmer Station has been sampling and studying the shelf ecosystem and physical environment since 1990. This dissertation seeks to improve our understanding of the subtidal and intraseasonal (hereafter defined together as 3-100 days) circulation on the neighboring continental shelf and is particularly motivated by the aims of the project to understand (1) how lateral transports of scalar parameters such as heat affect the vertical stratification and (2) how coastal canyon heads are linked to the larger-scale shelf circulation and why they are such ecologically productive environments. In this dissertation we study: (1) the origin and mixing of mesoscale eddies as agents of heat transport and stirring; (2) the spatial coherence of shelf-scale barotropic velocity fluctuations, their origin through flow-topography interaction with Marguerite Trough Canyon, and their associated heat transports; and (3) the wind-driven dynamics of the long-shore flow manifested through coastal trapped waves and their ability to both induce upwelling at a coastal canyon head and to modulate isopycnal depth at the continental shelf-break. This work takes an observational approach, utilizing the rare and expansive data set afforded by the long-term sampling program including shipboard CTD and ADCP profiles, moored current meter time series, and CTD profiles from an autonomous underwater vehicle.

As sea level rises, saltwater migration can threaten coastal ecosystems and beach-dune environments, which negatively impacts coastal flora. This study uses ground penetrating radar (GPR) to evaluate the spatiotemporal variability of saltwater migration in the near shore at high lateral resolution (i.e. cm) by using daily micro tidal cycles as analogs to infer saltwater migration. Time-lapse GPR profiles were collected at low and high tide capturing phase lags of the tidal flux through different substrates. GPR measurements were collected at two sites in Miami with contrasting lithologies: a) Crandon Park, composed of unconsolidated sand; and b) the Barnacle Historic State Park, composed of the Miami Limestone Formation. Laboratory-scale GPR measurements were collected over samples mimicking field conditions. The results may be helpful to identify regions vulnerable to saltwater migration in the near shore based on lithological variability, and to mitigate negative impacts for flora in beach-dune habitats during sea level rise. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection