Browsing by Author "Dr. Jay Levine, Committee Member"

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    Effects of Land Use and Land Cover on Freshwater Mussel Populations in the Upper Neuse River Basin, NC: A GIS Approach
    (2002-12-03) Andersen, Elizabeth F.; Dr. Hugh Devine, Committee Chair; Dr. Jay Levine, Committee Member; Dr. Heather Cheshire, Committee Member
    Land use practices can adversely affect water quality and freshwater mussel populations. Water quality can become degraded by siltation from development, pesticides and nutrients from agricultural fields, heavy metals and other toxins from urban runoff. The relationship between land use/land cover and freshwater mussel populations was investigated in the upper Neuse River basin in North Carolina. Mussel surveys were conducted from April to August of 2001 in the Eno, Flat, Smith, New Light, and Little River watersheds. Surveys (n=44) were conducted along 300-m transects upstream and downstream of bridges to examine the effect of bridge crossing structures on mussel assemblages. Geographic Information Systems (GIS) hydrological modeling tools were used to delineate upstream catchments of each sample site and to determine drainage areas. GIS was used to quantify land use/land cover within multiple spatial areas: upstream catchment, upstream riparian buffers (100 m and 250 m widths), and local riparian buffers (100 m and 250 m widths) immediate to the sample sites. Other environmental variables included stream slope, road density, water chemistry, and habitat quality assessment scores. No significant differences (p< .05) between mean mussel abundances due to location (upstream or downstream), distance from the bridge, or their interaction were observed in a split plot block design analysis. However, a slight decline in abundance was observed within the first 50 m downstream of the bridge. Future studies in additional subbasins of the Neuse and/or in other river basins could show a significant decline. Detrended Correspondence Analysis (DCA) and Nonmetric Multidimensional Scaling (NMS) ordinations described some of the variation in the mussel community structure (67% and 46% total variation respectfully). Both of the ordinations yielded similar community structures and environmental gradients. Moderate associations (r>.5) were observed between DCA and NMS axis 1 and several environmental factors including drainage area, localized urban regions, and habitat scores. Strophitus undulatus (Creeper) and Pyganodon cataracta (Eastern Floater) were the most strongly associated species with ordination axis 1 and occurred in sites characterized by small drainage areas, small habitat quality assessment scores, and low percentages of urban land cover immediate to the site. A GIS-based proximity analysis examined the relationship between mussel populations and distance to the nearest land cover type (urban, forest, row crop agriculture and non-row crop agriculture). Linear regressions revealed significant relationships (p<.05) between mussel assemblages and non-row crop agriculture (r², = .11) and urban land uses (r², = .11), but accounted for only 11% of the total variability in each case. Further investigation is needed to determine the environmental factors that contribute to mussel community structure. The study sampling design selected for highly forested areas. Inclusion of more urbanized regions could yield very different results. The upper Neuse study area was characterized by high mussel abundance and species richness and could be compared to other subbasins in the Neuse or other watershed in future studies. Repeat visitation to the sample sites could also investigate temporal and seasonal variations in mussel populations.
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    Investigating the Ecology of Naturally-Occurring Pathogenic Vibrio Species in Gulf Coast Oysters Through the use of Molecular Sub-Typing Techniques
    (2009-10-09) Whitney, Brooke Meredith; Dr. Jay Levine, Committee Member; Dr. Donn Ward, Committee Member; Dr. Lee-Ann Jaykus, Committee Chair; Dr. Todd Klaenhammer, Committee Member; Dr. Angelo DePaola, Committee Member
    Vibrio parahaemolyticus and V. vulnificus are ubiquitous marine-dwelling bacteria that cause human illness and are of particular concern when raw shellfish are consumed. These organisms can multiply in oysters during storage at ambient temperatures during harvest but prior to refrigeration. Oysters and seawater were collected from 2-3 Louisiana Gulf Coast sites seasonally over a two year period (2006-2007). Subsamples of oysters were placed on ice immediately following harvest (time 0) and then after 2.5, 5, 7.5 and 10 hours of on-deck storage at ambient air temperature. The purpose of the first study was to look at the changes in total and pathogenic V. parahaemolyticus that occur over ten hours of exposure to ambient temperature during harvest. Total V. parahaemolyticus levels were enumerated using the FDA-Bacteriological Analytical Manual (BAM) method for colony lift hybridization targeting the species-specific thermolabile hemolysin (tlh). Results show the highest increase in counts occurred during the summer season; observed levels of total V. parahaemolyticus in oysters averaged 1.7 x 102, 2.2 x 103, 7.5 x 102 and 2.5 x 102 CFU/g at harvest for winter, spring, summer, and fall seasons, respectively. After 10 hours of on-deck storage, these levels changed to 3.3 x 102, 1.9 x 103, 1.1 x 104, and 1.2 x 103 CFU/g for the same seasons. Pathogenic V. parahaemolyticus were enumerated using a multiplexed MPN-PCR targeting the thermostable direct hemolysin (tdh) and TDH-related (trh) genes. The average level of pathogenic V. parahaemolyticus at harvest were 0.027, 1.7, 0.21 and 0.040 MPN/g winter, spring, summer, and fall seasons, respectively; after 10 hours, these levels changed to 0.17, 0.21, 2.0 and 0.38 MPN/g for the same seasons. The percent of total V. parahaemolyticus which harbored pathogenic markers was 0.10% averaged over all seasons. Our data gives weight to the recent decision to reduce the time to refrigeration for Louisiana Gulf Coast oysters. The second study presented aimed to characterize V. parahaemolyticus strains isolated in the first study using pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). PFGE of the pathogenic (tdh+ and/or trh+) isolates revealed that many isolates were the same strain. Seventeen unique pathogenic strains and 16 non-pathogenic strains were chosen for MLST and further PFGE analysis. PFGE using the NotI restriction enzyme allowed for some grouping with respect to possession of the tdh gene. Twenty-one new sequence types were added to the online MLST database for future use. Both MLST and PFGE proved useful in this study in their own right. In a similar fashion, the third study was designed to characterize V. vulnificus stains isolated during the first study utilizing 16S – 23S rRNA intergenic spacer region (ISR1) typing and MLST. Overall, V. vulnificus showed a high degree of heterogeneity; no associations could be made using ISR1 typing with respect to geographical, temporal or isolation sources. However, grouping based on virulence factors (16S rRNA and vcg genotypes) could be made, although no significant exclusive groups were formed. MLST analysis revealed similar heterogeneity, with 46 new sequence types identified of the 51 isolates tested. ISR1 proved useful in grouping the otherwise heterogeneous V. vulnificus strains, while our additions to the MLST database are valuable for future use. We hope that our studies prove useful in the future: we would like to see our enumeration data used in future regulatory documents, while our characterization data adds to the growing knowledge of the ecology of pathogenic Vibrios.
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    A Multi-Scale Spatial Data Integration System for Park Management
    (2008-04-24) Blanchard, Margaret Elizabeth; Dr. Hugh Devine, Committee Chair; Dr. Jason Bocarro, Committee Member; Dr. Jay Levine, Committee Member