With continued marsh break-up and loss in Louisiana, small interior ponds are created, increasing areas of shallow water habitats. These shallow water habitats are potential sites for submerged aquatic vegetation (SAV) establishment. It is important to characterize nekton community composition, density, biomass, and growth within brackish marsh pond microhabitats because SAV is often cited as essential fish habitat (EFH). Three microhabitat types were investigated: (1) inner-pond SAV (> 1 m from edge); (2) near marsh-edge SAV (< 1 m from edge) and (3) nonvegetated bottom. We tested the null hypotheses that nekton community composition, density, and biomass were not related to microhabitat type and characteristics. Ninety-six quantitative samples were taken with a 1-m² throw trap between September 2001 and July 2002. The two vegetated microhabitats were characterized by monotypic stands of widgeon grass Ruppia maritima and contained similar biomass. Nekton community composition, density, and biomass did not differ between vegetated microhabitats, but differed significantly from the nonvegetated microhabitat (p < 0.0001). Therefore, SAV appears to be a dominant factor influencing nekton distribution within ponds. Submerged aquatic vegetation beds may also provide nekton with better growth environments by providing better quality or quantities of food for nekton than nonvegetated habitats. We also tested the null hypothesis that nekton growth was similar between vegetated and nonvegetated habitat types to determine if SAV provided a greater food resource than nonvegetated bottom. An in situ field experiment was conducted that compared growth rates of Atlantic croaker Micropogonias undulatus between vegetated and nonvegetated habitats to investigate the role of SAV in supporting nekton growth. We detected no statistically significant difference in nekton growth between vegetated and nonvegetated habitats (p = 0.125).

Understanding habitat needs of animal populations is critical for their effective management. In recent years, technological advances have increased the range of methods available to examine habitat selection patterns. However, available habitat data are often either limited to small geographic areas or are of coarse resolution, resulting in a gap in data to model habitat selection at landscape scales. I explored a method of processing Landsat data, the at-satellite reflectance tasseled cap, to address this data gap using black bears in south central Louisiana as a case study. As I showed, this case was particularly instructive because these bears occupy two very different habitat matrices. I examined the information content of resource measures derived from tasseled caps and determined that they contain substantially more information than is represented in coarse habitat maps such as available from the USGS GAP program. Additionally, this process could be applied over large areas and time frames, during different times of the year, and across sensors to produce consistent results that avoid the need to categorize land cover/habitats. I used logistic regression and the information theoretic approach to examine: the spatial scale at which habitat measures were derived, model complexity, and the relative value of groups of derived habitat measures. I grouped derived habitat measures to examine the information content in: images captured in two seasons, measures based on mean and standard deviation filters, and combinations of tasseled cap functions. My work suggests that researchers should consider multiple summary statistics derived over a range of scales, use multi-temporal data, and use all three tasseled cap functions to derive habitat measures. I calculated resource selection functions (RSF) for black bears in south central Louisiana and examined model calibration and discrimination. Mahalanobis distance has been proposed as an alternative to RSF because it does not require delineation of available resources, although results from the two approaches have not been compared. In this study, habitat quality predictions from RFS models more accurately depicted bear habitat preference than those of Mahalanobis. I propose an alternative use of Mahalanobis distance to direct model extrapolation beyond the boundaries of modeled populations.

Food abundance might limit survival or recruitment of wintering waterfowl. Nutritional requirements of wintering waterfowl have been estimated, but there are insufficient data on the abundance of seeds and submerged aquatic vegetation (SAV) to determine if enough habitat exists to support target populations of waterfowl throughout winter. I estimated waterfowl food abundance at 14 coastal freshwater marsh sites in Texas and Louisiana from August 2001 to March 2003, and tested the hypothesis that wintering waterfowl reduce food abundance. I analyzed 210 and 360 seed and SAV samples, respectively, taken during September 2001, February 2002, September 2002, and February 2003 to estimate seed and SAV biomass and determine if biomass declined during the winter. At one site, SAV biomass was estimated from 108 samples taken at six-week intervals (August-March) to provide another means of determining if food abundance declined throughout winter. Also at that site, 108 samples were taken from waterfowl exclosures in August and January of each year to provide another means of determining if wintering waterfowl reduce food abundance. Seed and SAV biomass estimates were not significantly different among time periods; biomass estimates of 14 genera of seeds and 8 genera of SAV collected averaged 244.2 ± 23.8 kg/ha (mean ± SE) and 262.3 ± 95.0 kg/ha, respectively. No significant differences in SAV biomass were detected among time periods at the six-week site or among time, treatment, and treatment by time interactions at the exclosure site. Mean food biomass estimates were well above the 50 kg/ha threshold estimate assumed to be the point of diminishing returns for feeding waterfowl. These findings also indicate that waterfowl did not significantly lower food resources in my study area over the two years of my study.

Chemical coupling plays an important role in improving interfacial bonding strength in wood-polymer composites. In this study, the effects of coupling agent type and structure, graft polymerization of coupling agents, interfacial wettability, coupling treatment and process, coupling agent distribution, and coupling agent performance on chemical coupling were investigated. Coupling mechanisms were established based on maleated polyethylene copolymers. For maleated wood veneer, the relationship among graft rate, concentration, and retention of coupling agent followed three-dimensional parabloid models. Wettability of maleated wood surface was related to acid number, amount of free or ungrafted maleic anhydride groups, and coupling agent concentration. Dynamic contact angle of water droplets on maleated wood followed the natural decay process, whereas the spreading process of droplets fitted the Boltzmann sigmoid model. Compared with untreated composites, maleated composites had significant shifts in most TGA, DSC, and DMA spectra because of chemical coupling at the interface. For melt-blending process, the best interfacial bonding strength was achieved at short compounding time (e.g., 10 min), appropriate mixing temperature (e.g., 180oC), and moderate rotation speed (e.g., 90 rpm). With FTIR, ESCA, and SEM analyses, the evidence of chemical bridges at the interface was proved. The interfacial morphology was illustrated with the pinwheel models. For wood-plastic laminates, interfacial adhesion followed the monolayer models, while brush, switch, and amorphous structures applied to melt-blended composites. Therefore, the interface was strengthened with covalent bonding (such as esterification and carbon-carbon bonding), strong secondary bonding (e.g., hydrogen bonding), macromolecular chain entanglement, and mechanical interblocking. Coupling agent performance for maleated copolymers was mainly related to their acid number, molecular weight, backbone structure, and concentration. Coupling agents with large molecular weight, moderate acid number, and concentration were preferred to have better performance at the interface. Based on the experimental results, 226D, 100D, and C16 were the best coupling agents among seven maleated copolymers used in this study. Compared with untreated composites, maleated composites increased interfacial bonding strength by 140% and flexural modulus by 29% at the concentration level of 3%.

To address public concern over potential ecological effects on commercially and ecologically important species following use of dispersants during oil spill response efforts, toxicity data was generated for three estuarine species indigenous to the Gulf of Mexico including juvenile Gulf killifish Fundulus grandis, white shrimp Litopenaeus setiferus, and Eastern oyster Crassostrea virginica. The acute toxicity of the dispersant Exxon Corexit 9500, South Louisiana crude oil (SLC), Alaskan north slope crude oil (ANSC) and dispersed oils (SLC+9500 and ANSC+9500) to the species was determined for both nominal concentrations (NC) and hydrocarbon concentrations (HC). Two 24-h field toxicity trials were conducted with the same species in a Louisiana coastal marsh, using ANSC and ANSC+9500, dosed at a NC of 30 ppm. White shrimp were more sensitive to dispersant, crude oils, and dispersed oils than killifish and oysters. The 96-h NC LC50 for crude oil and dispersed oil ranged from 370 to 4,500 ppm for killifish (HC 7.6 to 18.7 ppm) and 60 to 180 ppm for shrimp (HC 5 to 7.5 ppm). Mortality in oysters was not positively correlated with increasing levels of crude oils, or dispersed oils. Dispersed oils were more toxic than crude oils based on nominal concentrations, but no difference in toxicity of crude oils and dispersed oils was observed based on HC concentrations. No synergistic toxicity action was found between SLC or ANSC and dispersant Corexit 9500 based on HC concentrations. Survival was relatively high for all three species during the two 24-h field trials, generally exceeding 83% in crude oil and dispersed oil enclosures. Mortality of white shrimp was slightly higher than observed in killifish and oysters. The HC concentration in ANSC+9500 and ANSC enclosures ranged from 14 to 24 ppm and 10 to 11 ppm, respectively, at 0 h and declined to near 0 ppm in 3 hours. The rapid decrease was attributed to dilution from vertical mixing and tidal action. Both laboratory finding and field studies indicate that short-term exposure to nominal concentrations of ANSC or ANSC+9500 of 30 ppm or less are not likely to have an acute toxic effect on these species.

Previous studies have shown that pen-raised deer may be already predisposed to malnutrition at a higher rate then their native counterparts because they are normally raised on a pelleted ration and may not forage efficiently once released into wild habitats. Therefore, twenty pen-raised white-tailed deer that were offspring of deer obtained from Missouri (Odocoileus virginianus) were released onto a marsh pump-off habitat in southeast Louisiana (Da Bunch) to compare their diets to the diets of the native, wild, white-tail deer population already established in the area over four consecutive seasons to test this hypothesis. The microhistological analysis technique was used to estimate the botanical compositions of fecal pellets collected from both populations of deer located in the same range, over four consecutive seasons (Spring, Summer, Fall, and Winter) to account for seasonal variability. Native, wild and pen-raised deer diets averaged 78.2% similar during the year of the study, and were significantly associated to one another during each of the four seasons (P < 0.00001), indicating that all deer foraged on similar plant species in similar proportions. Differences were found in species frequencies per fecal sample, but for only five of the fifty-one species utilized significant differences were found (P < 0.001) between populations. Those species were Diodia virginiana in the spring, Aeschynomene americana, Ambrosia spp. during fall, and Berchemia scandens and Celtis laevigata in the winter. Both deer populations were predominantly grazers, with forbs constituting for a yearly average of 41.20% the deer diets. This study agrees with previous studies that concluded that translocated deer released into a new environment will adapt to the area and forage just as efficiently as the pre-existing deer population in the area assuming carrying capacity is not compromised.