Freshwater ecosystems, particularly streams and rivers, have been the subject of prodigious research. Unfortunately, in comparison to neighboring regions, the Gulf of Mexico coastal plain has not received as much attention. Therefore, I collected data on the macroinvertebrates of these streams to begin the understanding of the relationships between community structure and environmental characteristics. In contrast to the hypothesized ancestral streams of these macroinvertebrates, coastal plain streams are commonly devoid of rocks leaving only woody debris as usable hard substrates and are typically lower in dissolved oxygen. I examined habitat selection by colonization of woody debris with large and small surface areas. Secondly, given a similar surface area, I examined colonization in different levels of dissolved oxygen. Concurrently, I conducted biota and habitat surveys in three streams over four periods from August 2002 until April 2004 to collect baseline data for future investigations. The survey data included macroinvertebrate collections, microbial population estimations, water chemistry, and habitat descriptions. Finally, over the same time period, I collected macroinvertebrate, microbial, water chemistry, and habitat data in a stream with a potentially strong biotic disturbance, feral swine (Sus scrofa). All data were examined with appropriate multivariate statistics. The in-stream experiment suggested similar colonization of both sizes of woody debris for 20 of 21 taxa examined. Some potential high and low dissolved oxygen specialization was detected in the experiment, however, many macroinvertebrates (37%) appeared to be dissolved oxygen generalists. Further, survey data suggested more than 50% of collected macroinvertebrates also may be generalists with regard to other abiotic factors, but did demonstrate some affinity for woody debris. The single stream biotic disturbance appeared to significantly alter the macroinvertebrate community with a potential shift in favor of collecting organisms against scraping organisms. Therefore, in contrast with other regions, I suggest that coastal plain macroinvertebrates are tolerant to many abiotic factors, but are intolerant of some biotic disturbances.

Lake Pontchartrain and the drainage basin have experienced environmental degradation because of human settlement, land use and climate changes. A thorough understanding of hydrologic trends and variability associated with the changes is critical for sustainable water resources management and ecosystem restoration in the region. This study examined freshwater inflow (1940-2002) and suspended solids loadings (1978-2001) from three upper Lake Pontchartrain watersheds that contribute to the lake estuary: the Amite, Tickfaw, and Tangipahoa river watersheds. The relationships of freshwater inflow and suspended solids loadings with climate variables and population growth were investigated. Using observed daily discharge, a spatially-distributed hydrologic model (SWAT) was evaluated, and the model then was employed to assess hydrologic responses of the coastal watersheds to potential climate change. The study showed an annual freshwater inflow of 5 km3 yr-1 and average suspended solids inputs of 210,360 tons yr-1 entering Lake Pontchartrain. More than 69% of annual water yield and 66% of suspended solids occurred from December to May and from January to April, respectively. Over 80% of the variation in annual freshwater inflow could be explained by annual precipitation. A significant increase in freshwater inflow was found in the Amite River watershed over the past sixty years, coinciding with both climatic variation and population growth. The hydrologic modeling showed a good agreement between the simulated and observed daily discharge, with a relatively high Nash-Sutcliffe model efficiency (> 0.811) and low mean error (< 5.6%). The simulation further indicated that, unlike upland watersheds, calibration of the surface and channel routing parameters in the SWAT model became most critical for lowland coastal watersheds with gentle relief. The climate change assessment showed a significant influence of precipitation on annual freshwater yield with an increase of 19.3%-40.1% in response to a 10%-20% increase in annual precipitation. Potential air temperature increase would have only a marginal effect on freshwater yield as shown by a 1.4%-2.9% decrease in the annual freshwater yield for a 1.6 oC-3.3 oC increase in temperature. Warming, however, may pose risks of drought during spring and summer in this humid subtropical region.

Louisiana black bears (Ursus americanus luteolus) exist in 3 isolated populations in Louisiana and are listed as a threatened subspecies under the United States endangered species act. In order to establish a population of black bears in central Louisiana and to promote connectivity among existing populations 11 adult females and 28 cubs were reintroduced to suitable habitat on Lake Ophelia National Wildlife Refuge. We captured and monitored females in the Tensas River Basin (TRB) in northeast Louisiana for use in these reintroduction efforts and to study their ecology. Specifically, I studied the food habits, space use, habitat selection, and denning behavior of female bears in the TRB and reintroduced populations. Within the TRB bears exist in 2 subpopulations (Tensas and Deltic) which inhabit highly variable landscapes. Bears on Tensas inhabit a large (>300 km²) contiguous block of bottomland hardwood forest, whereas bears on Deltic inhabit small (<7 km²) forest fragments surrounded by a matrix of agricultural fields. Bears in the TRB ate an omnivorous diet dominated by plant foods that shifted to exploit seasonally available foods. Important food items included: herbaceous vegetation, soft mast, corn, acorns, and beetles. Spring home ranges and core areas on Tensas differed between females with and without cubs. Ranges of females on Tensas were larger than those on Deltic, and ranges of reintroduced females were larger than both TRB subpopulations. Habitat selection patterns also differed as females on Tensas selected swamps and regenerating forests at most spatial scales and during most seasons, whereas Deltic females selected upland and lowland forests. Lake Ophelia females selected upland and lowland forests when establishing home ranges, but did not exhibit non-random habitat use within home ranges. In the TRB, parturient females used tree dens more frequently than ground dens, whereas non-parturient used tree and ground dens with similar frequency. Tensas den sites were closer than expected to swamps, water, and regenerating forests, whereas Deltic den sites were closer than expected to upland and lowland forests. I discuss the results in relation to fragmentation, forest management practices, and conservation.

Increasingly, attention is being paid to the role coarse woody debris (CWD) plays in forest ecosystems. CWD has been shown to provide valuable wildlife habitat, support food webs and contribute to nutrient storage and cycling, and mediate hydrological and geomorphic process. Timber management may be altering CWD dynamics by replacing aging stands with younger, more vigorous ones. The specific objectives of this study were 1) to quantify differences in coarse woody debris characteristics among bottomland hardwood forest stands with different management histories, and 2) to determine how differences in tree species composition and forest structure in bottomland hardwood forests influence coarse woody debris characteristics. Transects were established in ten forest stands with different management histories. Line intercept sampling was conducted to evaluate CWD characteristics, and point-centered-quarter sampling was used to compare characteristics in live vegetation. Large standard deviations were associated with most parameters measured, but results suggested that stands that have not been recently managed support more characteristics associated with structurally mature forest than stands that have been recently harvested. In particular, the Bayou Cocodrie NWR old growth natural area expressed characteristics such as relatively large volumes of CWD, a relatively high frequency of large diameter logs, snags, and trees, and a more stratified canopy and established mid-story. More research is needed to better understand the inherent variability in CWD and live vegetation characteristics among bottomland hardwood forests before explicit correlations between forest management and CWD dynamics can be inferred.

Louisiana is the leading state in number of river otters used in reintroduction programs in other states and in the production of pelts. However, habitat loss and degradation have prompted concern about the status of otter populations. This dissertation undertakes a spatial and temporal analysis of river otter harvest activity and examines environmental factors related to monitoring mercury levels in streams in Louisiana. Harvest data for 1957-2004 were analyzed to identify spatial and temporal trends in otter harvest activity. Changes have occurred in the last 20 years in the spatial dynamics of otter harvest in Louisiana, these include an increasing proportion of harvested otters coming from upland parishes in more recent years, and an increase in the proportion of trappers catching otters in that region. Spatial analysis indicated that this shift in harvesting activity has been gradual rather than abrupt. An explanation for this shift could be a greater interest of upland trappers in catching otters because of increasing otter pelt price and a decline in pelt price for other furbearer species. Analyses indicated that a management plan based on spatial control of harvest could be an option in Louisiana, with rice fields and protected areas playing an important role in the management/conservation plan. Temporal analysis suggested that the number of otters harvested 1 and 5 years ago has an impact on number of otters harvested at present time. An autoregressive model was developed to describe this association and to forecast number of otter pelts to be harvested 1 year in the future. The structure identified in the harvest data was used to develop a model to describe the dynamics of the otter populations. The simulation using 4-year and 8-year periods offered a reasonable approximation to the estimated cyclic dynamics of otter population in Louisiana. Mercury levels in otters were compared to levels in fish collected in different streams in Louisiana. Mercury levels in otters were higher than in fish. Otter samples also identified streams where mercury level in water may require further analysis. These results suggested that a mercury monitoring program based on river otters could be feasible in Louisiana.

Female wild turkeys (Meleagris gallopavo) were captured and radio-marked in a bottomland hardwood forest in south-central Louisiana. Turkeys were monitored using radio telemetry from fixed points on Sherburne Wildlife Management Area, Atchafalaya National Wildlife Refuge, and Bayou des Ourses to observe seasonal patterns of space use, habitat preference and survival from 2002-04. The largest mean seasonal home range of 902.87 ha occurred during preincubation (15 Feb 9 Apr; n = 24) when females typically search for suitable nest sites, and the smallest mean seasonal home range was 434.12 ha, during brood-rearing (1 Jun 30 Sep; n = 32) when movement was limited by poults. Abundant herbaceous plant communities, resulting from mild winters likely allowed reduced home ranges (621.84 ha) during fall-winter (1 Oct 14 Feb; n = 18), whereas limited nest sites increased space use during preincubation. Low nest initiation likely contributed to relatively large home ranges (495.91 ha) observed during incubation (10 Apr 31 May; n = 25). Upland and lowland forests were selected by females when selecting home ranges, relative to habitat availability on the study area [1st order selection]. Lowland forest was selected during fall-winter, whereas upland forest was selected during the remainder of the year. Water-based forest, upland forest and openings were selected in core areas relative to habitats available in the home range [2nd order selection]. Openings were important during fall-winter and brood-rearing, whereas upland forest was selected during preincubation and water-based forest was preferred during incubation. Females consistently used water-based forest relative to habitat availability in their home ranges throughout the year [3rd order selection]. Mean annual survival was 0.59 from 6 March 2001 to 27 August 2004. Seasonal survival was greatest during preincubation (1.00) potentially due to increased habitat sampling and movement during this time period. Fall-winter survival was high (0.95), likely from mild winter climate and abundant herbaceous vegetation. Lowest survival occurred during incubation (0.80) and brood-rearing (0.85), primarily as a result of increased risks of predation associated with nesting and foraging broods.

Chinese tallow (Triadica sebifera) is a non-native invasive tree that is of particular concern in the Southeastern United States. It has become naturalized in a variety of habitats and can be found in monospecific stands. The use of tallow woodlands by overwintering birds is poorly documented. I compared use of tallow woodlands to use of bottomland hardwood forests by birds in the Mermentau River Basin, Louisiana. Species richness and evenness were greater in the bottomland hardwood sites. Three species were more abundant in tallow woodlands, six species were more common in bottomland hardwoods, and six species exhibited no difference between habitats. Information-theory methodology was used to determine the relative importance of woodland type and certain landscape variables to species richness and bird abundance. Model-averaged parameter estimates and relative Akaike weights were calculated. In most cases, woodland type was a better predictor of species richness and abundance than percent forest cover, distance to nearest forest patch, or the number of forest patches within 1 km. Energy assimilation of tallow fruit by captive birds was measured to determine if apparent metabolizable energy differed between bird species and plant species. Assimilation of tallow fruit pulp differed significantly between birds. Yellow-rumped Warblers (Dendroica coronata) exhibited the highest assimilation of tallow, followed by American Robins (Turdus migratorius) and then Northern Cardinals (Cardinalis cardinalis). Yellow-rumped Warblers, which where more common in the tallow woodlands, were able to metabolize tallow fruit more effectively than wax myrtle (Morella cerifera) and poison ivy (Toxicodendron radicans) fruit. Metabolization of wax myrtle and poison ivy fruit did not differ significantly. Cardinals metabolized deciduous holly fruit (Ilex decidua) more efficiently than either hackberry (Celtis laevigata) or tallow. Overall, bottomland hardwoods supported more bird species and exhibited a higher measure of species evenness. Tallow may provide an alternate food source for some species and could potentially influence the local winter distribution of Yellow-rumped Warblers.

The goal of this thesis was to evaluate temperature effects on cell proliferation of eastern oyster somatic tissues for the development of an oyster cell line. Understanding the in vivo cell proliferation of an organism is essential for the development of cell culture. Cell proliferation can be measured by identifying nuclear cellular proteins involved in growth regulation and cellular transformation. The primary objectives of this study were to: 1) develop an assay to evaluate cell proliferation, 2) develop an assay to analyze nuclear RNA content, and 3) evaluate temperature effects on cell proliferation in somatic tissues. Proliferating cell nuclear antigen was detected in all the phases of the cell cycle of the eastern oyster. The concentrations of PCNA increased from G₀/G₁ phase into the S phase, where it peaked in mid-S phase, and decreased in G₂/M phase. The immunohistochemically stained slides were analyzed using image analysis and compared to the flow cytometric detection of PCNA. Overall, flow cytometry was superior to immunohistochemistry in time and cost efficiency, and in sensitivity to the detection of PCNA in oyster somatic tissues. A flow cytometric assay was developed to detect nuclear RNA in oyster somatic tissues. Nuclear RNA was detected in all the phases of the cell cycle of the eastern oyster. The amount of nuclear RNA increased from G₀/G₁ phase into the S phase, where it peaked in mid-S phase, and decreased in G₂/M phase. Temperature effects on cell cycle, proliferation, and cell metabolism of oyster somatic tissues were evaluated. The cell cycle analysis of the heart and labial palps cells showed that the G₀/G₁-phase cells decreased as the S-phase and G₂/M-phase cells increased. The cell cycle analysis of both tissues also showed the opposite effect, as G₀/G₁-phase cells increased the S-phase and G₂/M-phase cells decreased. Heart and labial palps cells for oysters held between 10°C and 25°C increased in cell proliferation after one week of temperature fluctuation. The nuclear RNA/DNA ratio at all phases of the cell cycle for heart and labial palps cells for oysters between 15°C and 20°C was higher than at all other temperature regimes. Temperature fluctuations affected the cell cycle, proliferation, and the metabolic condition of oyster somatic cells.These results support the use of flow cytometry for the analysis of cell cycle, cell proliferation, and cell metabolism. The results also suggested that temperature fluctuation has an effect on cell cycle, cell proliferation, and cell metabolism. Future research needs to focus on improving the current in vivo study and adapt the assays for cultured cells.

This dissertation addressed comparative studies of sperm cryopreservation of diploid and tetraploid Pacific oysters, Crassostrea gigas, with an emphasis on the development of standardized and optimized protocols. This includes comparative ultrastructural differences between sperm from diploid and tetraploid oysters, methods for the rapid estimation of sperm concentration, optimization of cryopreservation, and evaluation of the mechanisms for sperm agglutination (formation of clumps or elongated "noodles") in thawed samples. Currently, cryopreserved sperm has not been commercialized in any aquatic species, and standardization and optimization could greatly benefit the potential commercialization of its use. In oysters specifically, cryopreserved sperm from tetraploids would facilitate the production of all-triploid seedstocks. In this study, sperm from tetraploid oysters were 25% larger in linear dimensions (lengths and widths), and 53% had 5 mitochondria compared to 4 in diploids. Spectrophotometric methods for rapid estimation of sperm concentration were developed and validated. The effects of cooling rate, single or combined cryoprotectants at various concentrations, equilibration time (exposure to cryoprotectant), straw size, and cooling method were evaluated for protocol optimization. Combination of the cryoprotectants polyethylene glycol (PEG; formula weight of 200) and methanol (for sperm from diploids) or PEG and propylene glycol (for sperm from tetraploids) were effective in retaining post-thaw motility only when PEG was at low concentrations (2-6%). Such effectiveness was especially manifested with sperm from tetraploids, for example, post-thaw motility as high as 50% was obtained with combined cryoprotectant. Sperm of tetraploid Pacific oysters were more susceptible to damage from cryopreservation procedures than were those of diploids, and male-to-male variation was significant for sperm from diploid and tetraploid oysters. Sperm agglutination was mainly due to the lack of sufficient cryoprotectant for specific sperm concentrations. These findings demonstrated the importance of standardization in sperm concentration and other procedures during cryopreservation. In addition, the systematic optimization of cryopreservation protocols involving interactions of multiple factors, recognition of male-to-male variation, and development of assays for sperm tolerance prior to freezing are all approaches important for the future potential commercialization of cryopreserved sperm in Pacific oysters and for other aquatic species as well.

Coastal forests in Louisiana are in decline due to natural and human caused changes in the hydrology of the region. Baldcypress and water tupelo trees have been further stressed by caterpillar herbivory in recent decades. Regeneration of water tupelo is crucial for cavity creation for nesting habitat for secondary cavity nesting bird populations. Insectivorous birds have been shown to decrease insect-caused leaf damage on trees in other ecosystems. Two experiments examining effects of insectivorous birds on tree growth were conducted in degraded areas of the Maurepas Swamp in southeastern Louisiana. In the first experiment, nest boxes were added to study plots in degraded swamp in an attempt to increase densities of secondary cavity nesting birds, and to determine if increased insectivorous bird abundance resulted in improved shoot growth of baldcypress saplings. Prothonotary Warblers were the only bird species to utilize nest boxes, nest boxes did not significantly increase densities of Prothonotary Warblers, and insectivorous bird abundance was not correlated with baldcypress shoot growth. In the second experiment, bird exclosures were erected around planted baldcypress and water tupelo seedlings. Leaf damage on trees within bird exclosures and those with an insecticide treatment was not significantly different from controls. Foraging observations of Prothonotary Warblers and Northern Parulas, and video nest monitoring of Prothonotary Warbler nests during caterpillar activity, suggest that birds demonstrate a functional response to baldcypress leafroller caterpillars. Results of video nest monitoring suggested that successful Prothonotary Warbler nests active during baldcypress leafroller activity have the potential to protect 76 grams dry weight of baldcypress foliage. However, birds only foraged on baldcypress taller than 2m, and forest tent caterpillars were only observed to be consumed during the first and final caterpillar instar stages. Planted baldcypress seedlings grew faster than planted water tupelo, and water tupelo seedlings had zero height growth, or died-back four times as frequently as baldcypress. Insectivorous birds provide baldcypress some protection from caterpillar herbivory, but birds may offer little protection to water tupelo, especially trees less than 2m tall.