Freshwater diversions are a relatively recently utilized tool in wetland loss mitigation that stimulate an organic accretion response in marsh vegetation, which is based in root production and thus belowground biomass. The effectiveness of freshwater diversions in slowing marsh loss probably varies across a gradient of the factors they supply: decreased salinity, increased nutrient concentrations, and increased inundation. Flooding stress is commonly thought to be the overriding factor limiting wetland vegetation growth, however its influence may vary across salinity and nutrients. Therefore, plugs of Spartina patens were planted in four marsh organs consisting each of 36 sediment-filled PVC pipes of incremental heights that created a range of growth elevation and thus flooding stress. The organs were located in mean salinities from 2.6-14.7 ppt and two of them fertilized at 22 g N m-2, 11 g P m-2, and 5.5 g K m-2. Twice during the growing season below- and aboveground biomass was harvested, sorted, dried, weighed, and analyzed for relationships between variables. Flooding stress was found to be primary, with a secondary interactive effect between salinity and fertilization that suggests fertilization may help plants resist relatively higher salinity levels. Variations in salinity and nutrient concentrations associated with freshwater diversions, which can differ in intensity and extent, might also be linked to increased nutria herbivory. Therefore, nutria preference for fertilized versus unfertilized vegetation was also tested in a controlled setting on Panicum hemitomon, Sagittaria lancifolia, and S. patens, representative dominant plant species of fresh, fresh-brackish, and brackish marsh. Nutria showed a significant preference for fertilized vegetation within species. It is therefore possible that benefits derived from nutrient-rich fresh floodwater could potentially be negatively impacted by increased preferential herbivory.

Research on blue crab diseases, parasites, and symbionts has been sporadic in the Gulf of Mexico. Understanding the prevalence of diseases, parasites, and symbionts is important for managers to set informed regulations for the commercial industry and to understand the impacts of environmental disasters on aquatic animal health. The objective of this research was to determine the prevalence of Lagenophrys callinectes, Urosporidium crescens, Hematodinium perezi, Loxothylacus texanus, reo-like virus (RLV), shell rot, and Vibrio spp. in crabs collected from four coastal locations and four shedding facilities in 2013 and the beginning of 2014. Additionally, I determined the prevalence of white spot syndrome virus (WSSV) in the wild populations. I also recorded infections by non-Vibrio bacteria and by Ameson michaelis. H. perezi, L. texanus, WSSV, and RLV were detected by polymerase chain reactions. Shell rot and U. crescens were detected by gross visual detection. L. callinectes and A. michaelis were identified by microscopy and Vibrio spp. and non-Vibrio spp. bacteria were detected by standard microbiological culture techniques and biochemical testing. No samples were infected with H. perezi, L. texanus, or WSSV. Based on the low salinities sampled, these results were expected for H. perezi and L. texanus. Shell rot and Vibrio spp. were moderately prevalent in the wild and captive crabs, but infections were more common in the captive crabs. U. crescens was never found in crabs from Lake Pontchartrain, the lowest salinity field site. It was also rare in crabs from the low salinity shedding facilities, indicating that this hyperparasite may be limited to moderate to high salinities. L. callinectes was ubiquitous with over 90% prevalence in wild and captive crabs. Reo-like virus infections were found in wild and captive crabs in the summer of 2013, and A. michaelis was present in two shedding facility pre-molt crabs. Overall, Louisianas blue crab nearshore populations appear to be healthy with no parasitization by the two most ecologically and economically detrimental parasites, H. perezi and L. texanus. However, in the future, RLV needs to be extensively studied because it is also capable of decimating blue crab populations.

The processes that control species composition and structure in wetland ecosystems are complex and controlled by many factors including seasonality, depth and duration of flooding, and nutrient dynamics. Catahoula Lake is a floodplain lake that has existed with seasonally fluctuating water levels for at least 4,000 years. The herbaceous vegetation that attracts these waterfowl is slowly being outcompeted by woody vegetation, most notably water-elm (Planera aquatica). Our general goal is to understand the processes that cause this shift, focusing on the role of sediments. Our first objective was to use historical aerial imagery to detect historical changes in plant communities at Catahoula Lake, focusing on timing and rates of expansion of woody vegetation. Aerial imagery indicated woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased 249% since major hydrologic alterations in the 1960s. There are three local patterns to this expansion: continuous expansion of woody vegetation, long-term stability of the tree line, and complex patterns of tree establishment. Second, we used 137Cs in lakebed sediments to calculate rates of sedimentation. Results indicated sedimentation was 0.26 cm yr-1, which is increased 225% from the pre-settlement rate of 0.08 cm yr-1. Peaks of 137Cs were muted and deposition rates were similar around the lake, suggesting redistribution of sediments is common. Third, we investigated elemental concentrations in sediment which revealed little spatial variation in recent sediment, but a shift from mixed coastal-plain and Mississippi Alluvial Valley sediments to dominance by acidic, coastal-plain sediments in the past ~60 yr. Sediments are low in organic matter, and carbon and nitrogen concentrations decrease with depth and are being sequestered at low rates (840 t yr-1 and 120 t yr-1, respectively). Compared to its condition prior to hydrologic alterations beginning in the 1920s, Catahoula Lake is about 15 cm shallower and the chemical composition of sediments is more acidic. Although these results are not sufficient to link these differences directly to ecological changes, it is likely the altered sedimentary and hydrologic environment is contributing to the increased dominance of woody vegetation.

Changes in the timing and interaction of seasonal high temperatures and low salinity as predicted by climate change models could dramatically alter oyster population dynamics. Little is known explicitly about how low salinity and high temperature combinations affect spat (<25 mm), seed (26-75 mm), and market (>75 mm) oyster growth and mortality. Using lab and field studies, this project quantified the combined effects of extremely low salinities (< 5) and high temperatures (>30 oC) on growth and survival of spat, seed, and market-sized oysters. In 2012 and 2013, hatchery-produced oysters were placed in open and closed bags at three sites in Breton Sound, LA, along a salinity gradient which typically ranges from 5 to 20. Growth and mortality were recorded monthly. Regardless of size class, oysters at the lowest salinity site (annual mean = 4.8) experienced significantly higher mortality and lower growth than oysters located in higher salinity sites (annual means = 11.1 and 13.0); furthermore, all oysters in open bags at the two higher salinity sites experienced higher mortality, likely due to predation. To explicitly examine oyster responses to extreme low salinity and high temperature combinations, a series of laboratory experiments were conducted. Oysters were placed in 18 tanks in a fully crossed temperature (25oC, 32oC) by salinity (1, 5, 15) experiment with 3 replicates, and repeated twice for each oyster size class. Regardless of temperature, seed and market oysters held in low salinity tanks (salinity 1) experienced 100% mortality within seven days. In contrast, at salinity 5, temperature significantly affected the mortality rate; all size class oysters experienced > 50% mortality at 32 oC, and < 40% mortality at 25 oC. In higher salinity tanks (15), only market-sized oysters held at 32 oC experienced significant mortality (>60%). These experiments demonstrate that high water temperatures (> 30 oC) and low salinities (< 5) negatively impact oyster growth and survival, and that high temperatures alone may negatively impact market-sized oysters. It is critical to understand the potential impacts of climate and anthropogenic changes on oyster resources in order to better adapt and manage for long-term sustainability.

The population of Bald Eagles (Haliaeetus leucocephalus) nesting in Louisiana reached precariously low numbers in the early 1970s, and although the population has since increased markedly, resident eagles remain a species of conservation concern in Louisiana. Using statewide aerial nest survey data from 19752008, I documented the history and quantified the recovery of the nesting population in Louisiana. Known active nests increased exponentially from 7 to 387 during this period, exhibiting a mean annual rate of increase of 11.1 ± 0.3% per year with no indications of slowing. By 1990, the nesting population in Louisiana had exceeded all goals of the Southeastern States Bald Eagle Recovery Plan. I used nest location and status data from the most recent year (20072008) of the nest monitoring program to examine landscape level nest site selection and success. Success of a nest was not greatly influenced by the physical characteristics around a site, whereas the initial selection of a nest site was most influenced by distance to the historical nest centroid and the proportion of open water and agricultural land within 3 km. Bald Eagles nest during the winter in Louisiana, but they are rarely observed in the state during summer. Therefore, I used satellite GPS transmitters to provide evidence of their undocumented summer migrations and examined parameters such as timing of departure and arrivals, stopover use, routes used, and seasonal and annual variations in these parameters. Marked eagles flew relatively direct routes, exhibiting high route fidelity going between Louisiana and their summering areas, which were spread out across much of Canada and south to Illinois. Using locations from their winter and summering areas, I estimated home range and core area size. Home ranges varied from 19.71,997.7 km2, but nesting Bald Eagles had smaller home ranges, on average, than did non-nesting birds. The sex of an individual can play an important role when considering variations in movements, home ranges, and habitat use. Accordingly, I evaluated the published field technique for sex determination of Bald Eagles, and upon documenting misclassifications, I developed a new formula applicable to Louisiana and other southern regions.

The blue crab (Callinectes sapidus) is a commercially, recreationally, and ecologically important species in Louisiana coastal waters. Louisiana landings account for more than 80% of Gulf of Mexico hard crab landings. In 2012, over 24 thousand metric tons of blue crab were landed in Louisiana with an economic value over $52 million. The blue crab fishery in the northern Gulf of Mexico relies heavily on Atlantic menhaden (Brevoortia tyrannus) for bait, which is a species with stock concerns resulting in approximately a 20% decrease in total allowable catch beginning in 2013. Decreased landings results in increased cost of B. tyrannus for industrial and bait uses, demonstrating a need for new cost-effective alternative bait. Large amounts of waste are produced from processing over 40 thousand metric tons of penaeid shrimp annually landed in Louisiana. Shrimp carapace accounts for approximately ¨ö to ¨ø of the total biomass and can be used an attractant in alternative bait. The objectives of this study are: 1) determine a feasible attractant utilizing seafood processing waste; 2) determine if alternative bait soak time, diffusion, and catch will perform similar to B. tyrannus; and 3) Determine fishermen opinions and preferences for an alternative bait. Crabs responded favorably to bait created with shrimp waste as the attractant in laboratory choice bioassays. Field trials in three temperature regimes demonstrate soak time of alternative bait is comparable to the current natural bait used by the industry. Additionally, the alternative bait diffuses proteins, which stimulate feeding in crabs, at levels similar to or higher than natural bait. Paired-trap field trails demonstrated alternative bait produces catch rates comparable to natural bait; shrimp alginate accounted for 41% of total catch. Additionally, reduced rates of bycatch were seen in traps baited with alternative bait. Interviews conducted with commercial fishermen indicate the industry is willing to use alternative bait. Current results show a bait created with a waste product as an attractant is feasible. Alternative bait would benefit blue crab fishermen, B. tyrannus stocks by reducing fishing pressure, and processors by creating a value added product.

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Wind is now established in Europe as a major 'renewable energy' resource, but its large scale exploitation is increasingly limited by environmental issues. Hence, on the way to a more sustainable development, it is desirable to seek ways to incorporate it into small scale embedded generation. As a first step, a prototype of a small scale Ducted Wind Turbine has been developed and tested, which seems to be feasible for integration into a conventional building. The wind flow around the building generates differential pressures which may cause an enhanced massflow through the turbine. This thesis is concerned with the investigation of the flow through building integrated duct configurations. Hence, pressure and wind speed measurements have been carried out on a wind tunnel model at different angles of incident wind. Different duct geometries with attached spoilers have been tested, and it was confirmed that wind speeds up to 30 % higher than in the approaching free stream are induced in the duct, in some cases tolerating an angle of incident wind up to 60°. The experimental work proceeded in parallel with Computational Fluid Dynamics modelling. Adaptive gridding of the complex full model geometry required a two dimensional approach, which was used to compare the predicted flow behaviour qualitatively. Three dimensional simulation of the flow field in the building integrated duct could be compared with experimental results. A new flow field mapping approach was initialised to form a two stage process in which conditions in the large-scale flow domain, modelled in a coarse three dimensional simulation, are used as boundary conditions for a localised simulation of the duct flow. Based on performance measurements of a free standing prototype in field trials and the experimentally determined wind speed in the duct, a power prediction model was developed. For the Scottish climate, the proposed device compares favorably with conventional small wind turbines and photovoltaics. The presented work evaluates the concept of harvesting wind energy in the built environment and provides outlines for the future design of a building integrated Ducted Wind Turbine module.

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