Tesis profesional--Universidad Nacional Autonoma de Mexico, 1965. / Includes bibliographical references ([final 3 leaves ]).

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: James J. O'Brien, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 15, 2006). Document formatted into pages; contains ix, 78 pages. Includes bibliographical references.

Thesis (M.S.) in Computer Engineering--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 55-57).

Sediment transport and slope stability are fundamental organizing agents of the geological record. These processes have been extensively studied along the northern margin of the Gulf of Mexico basin for both basic and applied purposes, but our knowledge of them is limited by the spatial and temporal sampling capabilities of traditional geologic oceanographic surveying tools such as coring, single-beam echosounders, and sidescan sonar. This dissertation seeks to update the state of knowledge regarding northern Gulf of Mexico sediment transport and slope stability from annual to millennial timescales, primarily using relatively high-resolution acoustic geophysical tools such as swath bathymetric echosounders and swept-frequency subbottom echosounders. There are three primary findings of this dissertation: (1) the subaqueous Mississippi River Delta Front is a zone of active downslope sediment flux in lieu of major hurricane passage, and the volume of sediment transported downslope during major hurricane and non-major hurricane containing intervals is comparable, (2) mud-capped dredge pits used for coastal restoration projects in Louisiana can be used as proxies for sediment deposition and slope stability along the Inner Continental shelf, and highlight the important role resuspension and slope failure play in decadal and longer-scale sediment accumulation in this environment, and (3) a drowned forest of age > 40,000 years before present found offshore Gulf Shores, Alabama likely represents a unique or at least fairly localized depositional environment that preserved entire tree stumps during geologic periods that favor destruction of sedimentary fabric, including sea level lowstand and transgression.

Coastal marshes can have high rates of carbon (C) accumulation associated with high primary productivity and sedimentation rates, and low rates of microbial decomposition. Mitigation for the loss of saline marshes by restoration and creation is becoming widespread; however, a greater understanding of the timescale and capacity for these new sites to function as C sinks is needed. For this study, we examined a chronosequence of six created coastal marshes ranging from 0 to 32 years old and two adjacent natural marshes in Sabine National Wildlife Refuge in the Chenier Plain of Louisiana. We collected soil cores in created and natural marshes (n = 6) and measured bulk density, total organic C and nitrogen (N), particle size, organic matter content, and fatty acid methyl ester relative abundances in all cores. To calculate longer-term carbon accumulation rates (LCAR), we used the known age of created marshes and measured Cesium-137 in natural marsh cores. Short-term carbon accumulation rates (SCAR) were measured using feldspar marker horizon plots. Relationships among soil C accumulation, microbial communities, and environmental factors, including vegetation, salinity, hydrology, and elevation, were also examined. Created marshes LCAR ranged from 18 to 99 g C m-2 yr-1, and did not significantly differ among marshes of different ages (p > 0.05). We observed high spatial variability of both SCAR and LCAR within created marshes, with stem density contributing the most to the variability in created marsh LCAR (p = 0.01). All marshes contained distinct microbial community compositions (p < 0.001), with soil C to N ratio associated with higher total microbial abundance, and plant species, elevation, and marsh age associated with shifts in dominant microbial groups. The data suggest that the establishment of vegetation with high stem densities, such as Distichlis spicata and Spartina patens, may facilitate higher LCAR in created marshes, which may be of interest for project planning in relation to C credits. This study also provides foundational information regarding microbial community dynamics in created wetland soils, which will support future research on the links between community composition and ecological processes such as blue C accumulation.

Salt marshes in the northern Gulf of Mexico provide critical habitat for many species, including those of economic and ecological interest. However, it remains both a critical and challenging task to quantify the carbon flow from various primary producers to higher trophic levels in such a complex system. Trophic biomarkers, which are measurable tracers of an organisms diet, are used to study energy flow in food webs. In the first part of this thesis, three trophic biomarker techniques (bulk stable isotope analysis of C and N, compound-specific stable isotope analysis (CSIA) of amino acids, and fatty acid analysis) were compared in the characterization and quantification of different carbon sources that support the salt marsh consumer, the seaside sparrow (Ammodramus maritimus). The results of this study show that, while fatty acids can provide qualitative information about an organisms carbon sources, only the stable isotope methods can quantitatively estimate them. Further, CSIA provides more precise estimates than bulk SIA. However, all three trophic biomarker techniques indicated that both terrestrial and aquatic carbon was important to the seaside sparrow. In the second part of this thesis, CSIA of amino acids was used to quantify carbon sources for a variety of terrestrial and aquatic salt marsh taxa in order to determine how terrestrial primary production may support aquatic consumers and vice versa in the salt marshes of Barataria Bay, Louisiana. The results of this study indicate that terrestrial and aquatic consumers rely on different carbon source profiles, with plant carbon found almost exclusively in terrestrial taxa and phytoplankton carbon found almost exclusively in aquatic taxa. Carbon from detritus and from benthic microalgae was found in both terrestrial and aquatic consumers, suggesting that these sources provide important links between the terrestrial an aquatic sectors of the marsh food web. Quantifying the carbon source pools of marsh consumers will help constrain models of energy flow which aim to predict how changes in primary production or food web structure will affect populations of interest.

Wetlands provide an abundance of ecosystem services, including valuable habitats for wildlife, water quality improvement through biogeochemical cycling, flood protection, high rates of primary productivity, and sequestration of carbon and nitrogen. Louisiana contains 40% of the lower 48 United States coastal and estuarine wetlands and also has the highest rates of wetland loss, ~ 80% of the nations total loss. Approximately 4900 km2 of coastal land in Louisiana has been lost since 1930. In the first project the study location, Barataria Bay, has one of the highest coastal wetland loss rates in the nation and therefore is a high priority for wetland restoration. Sediment dredged from the bed of the Mississippi River was placed at targeted locations in Barataria Bay and we sought to determine how comparable these dredged river-sediment marsh soils are to those of the surrounding natural marshes. Percent organic matter in the created marsh was 11.6% of the natural marsh. In the created marsh, the β-glucosidase enzyme activity was 10.3% and soil oxygen demand was 11.2% of the natural marsh, reflecting significantly less soil microbial processes within the created marsh sites. These data provide a baseline for monitoring and eventual determination of the trajectory for development of microbial-driven ecosystem services of created wetlands using dredged river sediment. Nitrogen loading from the Mississippi and Atchafalaya Rivers leads to an area of hypoxia each summer in the Northern Gulf of Mexico. Riparian wetlands within the Mississippi-Atchafalaya watershed could play an essential role in the reduction of nitrate released into the Gulf each year. However, much river-riparian wetland connectivity has been reduced through the building of levees. In an effort to restore these riparian systems, projects are focused on reestablishing the hydrologic connection of the river channel and riparian systems. The second project study location is located within the Atchafalaya River Basin, where these riparian wetlands will be reestablished with the Atchafalaya River. Results suggest that potentially 107 metric tons of N could be removed from the ~2023 hectare Atchafalaya Nature Preserve over a 3 month flooding period.

Fish experiencing blooms of the cyanobacteria genera Microcystis and Anabaena acquire microcystin and saxitoxin through ingestion of contaminated food and absorption of dissolved toxin. Even low chronic doses induce sensory and motor impairmentthe impact of which is unquantified in wild populations. Here, I introduce Lagrangian particle models for cyanobacteria and fish which test the hypotheses that impairment symptoms suppress movement and growth. This is implemented within the Finite-Volume Coastal Ocean Model (FVCOM). Cyanobacteria particles move vertically according to mixing and buoyancy (a function of cellular reservoirs). Fish navigate the horizontal domain, foraging in high growth areas, and fleeing when toxin increases. The framework is demonstrated here for the case of juvenile fish encountering <i>Microcystis aeruginosa</i> in an idealized Louisiana estuary. Self-shading reduces bloom growth, and causes algae to collect at the surface. Turbulent diffusivity is insufficient to break up this layer, so dissolved toxin becomes surface-intensified. Fish seek high growth areas in this environment, and dietary uptake increases. This triggers flight and swimming impairment. As cyanobacteria excrete microcystin, absorption forces fish to become intoxicated even in areas of lower toxic risk. Repeated flight means fish spend more time in suboptimal areas, with final growth reduced up to 6.6%. <i>In vivo</i>, this would be exacerbated by physiological stress and the metabolic cost of toxin removal. Collective movement (group diffusivity) is suppressed nearly 50% during wide-spread intoxication. Simulations show that within a certain parameter space, both movement and growth are suppressed relative to the control case as expected. However, additional experiments resulted in higher growth, indicating the methods are sensitive to model parameterization. Ultimately, these are sandbox cases, which will require carefully-designed lab and field experiments before predictive capability can be assumed.

The mangrove forest gap dynamic model, FORMAN, was the first individual-based model (IBM) to simulate the long-term successional dynamics of three Caribbean mangrove species, Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle. Assumptions under the spatially implicit approach of gap dynamic models limit their application to small-scale simulations. An expanded, spatially-explicit version of FORMAN was developed to allow for simulations of larger spatial grids, through the inclusion of localized soil conditions and neighborhood-based light resource competition. This expanded model was used to investigate the influence of localized interactions and disturbances of varying size on forest dynamics. A data-model comparison using field data from the Shark River Estuary in the Florida Coastal Everglades (FCE) tested the models ability to predict spatial relationships (inter-tree distances) based on tree size and species. The structure and function of the simulated mangrove forests were sensitive to complex interactions between localized soil and light competition based on neighboring trees. Under spatially varying soil conditions, neighborhood-based light competition limited tree growth (especially that of A. germinans and L. racemosa) in favorable soil zones, while allowing for sapling establishment in less optimal habitats. Forest recovery rates following disturbance were sensitive to both soil stress and disturbance size. L. racemosa experienced the greatest increase in annual productivity following disturbance, and exhibited a positive relationship between post-disturbance structure (biomass and basal area) and disturbance size. There was good agreement between the model and field data for frequencies of inter-tree distances and for the distribution of inter-tree distances when examined by size-class and by each species within sizes classes. However, there were no consistent differences or trends in inter-tree distance probability distributions observed across size-classes or for species within size-classes. The expanded FORMAN model, while still limited to the km2 scale in scope, is a very first step in increasing its spatial capability beyond the gap scale. This expansion potential is important in the context of climate change, as IBMs have been suggested as potentially useful tools in identifying and minimizing inaccuracies resulting from current methods of scaling biomass and productivity estimates from site to continental scales.

TOPEX/Poseidon (T/P) sea surface height (SSH) measurements along tracks 91 and 15 crossing the West Florida Shelf (WFS) are used to estimate seasonal across-shelf SSH gradients. These gradients and the knowledge that geostrophic flow approximately follows the isobaths enables an estimation of the seasonal along-isobath geostrophic flows. The seasonal geostrophic along-isobath flows are found to be highly correlated with the seasonal along-shore wind stress. Southeastward directed along-isobath flows are predicted in December, January, February, and March. Northwestward directed along-isobath flows are predicted in June, August, and September. The along-isobath geostrophic component of the flow is small in the remaining months. Karenia brevis, the Florida red tide organism, usually blooms on the south/central WFS in the summer and fall months. It is likely that the northwestward along-isobath flow in June, August, and September transports the red tide blooms northward to the Big Bend shelf region during these months. K. brevis blooms in 2005 and 2006 are used as a case study to examine the northward transport mechanism. Above average northwestward along-shore wind stress caused by hurricane activity in the Gulf of Mexico most likely resulted in the northward transport of K. brevis in 2005 while below average along-shore wind stress in 2006 suggests why a K. brevis bloom on the central WFS was not observed farther north. / A Thesis submitted to the Department of Oceanography in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2007. / February 2, 2007. / Satellite Oceanography, Harmful Algal Blooms, Red Tide, TOPEX/Poseidon, West Florida Shelf, Geostrophic Flow / Includes bibliographical references. / Allan J. Clarke, Professor Directing Thesis; Richard Iverson, Outside Committee Member; Doron Nof, Committee Member; William K. Dewar, Committee Member; Michael J. Sullivan, Committee Member.