It is thought that a lactate shuttle complex of Basigin gene products and Monocarboxylate transporter 1 (MCT1) is necessary for photoreceptor cell maturation and function. The purpose of this study was to investigate the assembly of the lactate shuttle by determining which amino acids within Basigin interact with MCT1. It has been hypothesized that these two membrane proteins interact via the transmembrane domain of Basigin. Therefore, a full-length histidine-tagged peptide of the transmembrane domain (24 amino acids), as well as histidine-tagged deletion mutants were generated using the pET1 02/0 vector (Invitrogen) to test for binding to MCT1 via enzyme-linked immunosorbent assay (ELISA). The probe containing the entire transmembrane domain of Basigin (amino acids 1 to 24) did interact with MCT1. An interaction was also observed when a probe containing amino acids 13 to 24 of the Basigin transmembrane domain was used. A comparable interaction was observed when amino acids 19 to 24 were used as a probe, but no signal was observed when amino acids 13 to 18 were used. This indicates that some or all of the six C-terminal amino acids of the Basigin transmembrane domain bind to MCT1. Site-directed mutagenesis of each of the six C-terminal amino acids, and subsequent ELISA analysis, . indicates that isoleucine - 20, isoleucine - 21, isoleucine - 23, and tyrosine - 24 interact with MCT1. Vlll

Fundulus heteroclitus and the closely related F. grondis are mainly distributed along the Atlantic coast of the U.S from Maine to Northeast Florida and from the East coast of Florida throughout the Gulf of Mexico, respectively. Both are resident salt marsh fishes whose range is thought to overlap in Northeast Florida, making them an ideal study system to examine resource partitioning between two closely related species. The objective of this study was to examine the effects of temperature and elevation on potential habitat partitioning of these two species. It is hypothesized that the northern species, F. heteroclitus, would have a lower thermal tolerance than F. grandis and would be found in lower marsh elevations, which are thought to be slightly cooler. Fundulus heteroclitus larval and juvenile distribution was examined and elevation was found to be significant (p the distribution with smaller fish utilizing higher elevation areas. Temperature was not found to differ between elevation sites, thus could not account for elevational differences. To further determine the role of temperature in Fundulus distribution, both species were hatched in the laboratory, and larvae were used for critical thermal maxima trials. F. heteroclitus from one population bad significantly higher mean loss of equilibrium (LOE) temperatures (pF. grandis populations. Due to population differences results could not be pooled by species. Critical thermal maximum temperatures show that both species can tolerate roughly the same extreme high temperatures and, based on temperature alone, should be able to live in the same habitat. Temperature tolerance of both species was higher than the actual measured field temperatures and is therefore not a likely factor in determining both species' range. A combination of other abiotic factors and biotic interactions such as competition may play a greater role in determining the observed range of each species than previously thought.

The purpose of this research was to study the potential negative effects that mesopredators have on their environment and to promote control of mesopredator populations. Overabundant predatory species such as the raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) can have significant pernicious effects on populations of autochthonous prey species, particularly when super predators such as the red wolf (Canis rufus) and Florida panther (Felis concolor coryii) are absent. These overabundant species, coined as mesopredators, are often responsible for extreme levels of predation on prey species and/or their young. The mesopredator release hypothesis involves the "release" or increased density of a generalist/opportunistic consumer species. This release hypothesis has two main predictions: first the absence of top predators lowers nest success of prey populations; the second there is a subsequent positive relationship between hyperabundant mesopredators and nest/prey predation. This phenomenon occurs because super predators such as the wolves and big cats have been driven to extinction or extirpation. To study the effects of mesopredators I used several approaches. Overabundant raccoons (29) were removed from a known diamondback terrapin (Malaclemys terrapin centrata) nesting beach to evaluate the reduction in terrapin nest predation. Next, I studied age structure, stomach content, and parasite load of the removed raccoons to determine several criteria. By determining the negative impacts such as over-predation of listed and ecologically important species and mesopredator potential to spread infectious diseases and parasites, I hope to promote population control of these animals. Analysis of sex ratios showed that adult males dominant (6/23). Gut content analysis showed that raccoons partook in over 11 different prey items including terrapin hatchlings. The parasite load included five nematode species, one acanthocephalan, and one cestode, and two protozoan parasites. Several parasites found pose a threat to human health and the control of such species is a concern. By studying mesopredator life history traits (population age, diet, and parasite population) we hope to understand the various negative effects it may place upon its environment. With this knowledge, further research and possible control methods may be proposed.

The National Oceanic and Atmospheric Administration (NOAA) is tasked with upholding the regulations prescribed in the Marine Mammal Protection Act of 1972. One of the ways this is accomplished is by producing regular stock assessment reports. For these reports, knowledge about a species abundance and distribution is a vital component, allowing informed management decisions to be made that may potentially reduce the natural and anthropogenic impacts on the organisms. In 2010, an Unusual Mortality Event (UME) occurred in the lower St. Johns River, resulting in an unusually large number of bottlenose dolphin strandings. As the data regarding this population was outdated, the cause of the UME could not be positively determined. Consequently, this lack of information provided the impetus to focus research on the individuals within the lower St. Johns River. Chapter one documents the abundance and emigration rates of the bottlenose dolphin population within the St. Johns River in order to provide NOAA with the necessary information to update the stock assessment report for this population. To designate individuals to various stocks, their distribution must first be known. However, many previous home range studies limited the size of the study area surveyed, which resulted in underestimates of the home range sizes. Therefore, in chapter two I investigated the effects that study area size has on the home range estimates of bottlenose dolphins while demonstrating the usefulness of collaborative science. Together these two chapters report data on the bottlenose dolphin population within the St. Johns River that has not been studied in over 16 years and this research also reveals how study design impacts various analyses and perceived outcomes.

Skeletal muscle wasting occurs as a corollary of numerous physiological conditions, including denervation, immobilization, and aging. The E3 ubiquitin ligases MuRF1 and MAFbx are induced under nearly all atrophy conditions and are believed to play a key role in protein degradation. Data in this thesis provides interesting new evidence that MuRF1 may also act as a transcriptional modulator of atrophy-induced genes or atrogenes. The transcriptional regulation of MuRF1 and MAFbx were characterized using a reporter gene system and exhibited repressed activity in C2C12 cells overexpressing MuRF1. Furthermore, ectopic expression of the myogenic regulatory factors (MRFs), MyoD and myogenin, caused significant activation of the MuRF1 and MAFbx reporter gene constructs, while co-overexpression of MuRF1 with MRFs resulted in reversal of MRF induction of reporter gene activity. Interestingly, ectopic expression of a catalytically dead MuRF1 RING mutant failed to reverse MRF activation of the reporters, suggesting that ubiquitin ligase activity may be necessary for MuRF1 transcriptional regulation. To further investigate a potential mechanism of MuRF1 regulation of MRF activity, Western blot analysis was performed to analyze MRF protein levels in C2C12 cells overexpressing MuRF1 and MuRF1 RING mutant. Cells with ectopic MuRF1 or MuRF1 RING mutant showed repressed levels of myogenin. Additionally, cells overexpressing MuRF1 and MuRF1 RING mutant treated with MG132 showed only a partial rescue of myogenin protein levels. Finally, chromatin immunoprecipitation was performed to analyze occupancy of MRFs at the MuRF1 promoter. Overexpression of MRFs resulted in increased MuRF1 promoter immunoprecipitation (IP) and amplification, while co-overexpression of MuRF1 with MRFs resulted in a reversal of promoter IP and amplification. These findings suggest that MuRF1 may regulate MRF transcriptional activity in a non-canonical fashion giving insight into a potentially new mechanism by which MuRF1 may act to transcriptionally regulate atrophy-induced gene expression.

The demography and reproductive biology of the gopher tortoise (Gopherus polyphemus) was studied for two years at White Oak Plantation (WOP), located in northeast Florida along the St. Mary’s river. Two sub‐populations were studied in regions I referred to as Site A and Site B. I located 312 burrows and captured 109 different tortoises, either by hand or using bucket traps. Tortoise density was 4.48/ha at Site A and only 1.15/ha at Site B. Juveniles were the most abundant age class overall, while hatchlings were numerous at Site A but virtually absent at Site B. The combined sex ratio for adult tortoises at WOP was 1:1.55 (F:M). Six nests were discovered over the course of the study, all located at Site A. Mean clutch size was 3.8, much lower than other studies conducted in Florida and Georgia, but egg hatching success (87.5%) was comparable to other studies. Growth rates were mostly consistent with other studies for juvenile, sub‐adult and adult age classes, but were unusually high for hatchlings. In light of the fact that habitat fragmentation is currently one of the leading threats to tortoise populations, I propose management recommendations that will merge these two sub‐populations and lead to increased potential and gene flow for their long‐term viability.

Stress has been identified as one of the primary factors influencing the structure of food webs, but few conclusions about the effects of stress on community dynamics have emerged. This study examined generalities that exist between salt stress and insect herbivore responses. Ambient salinity was artificially increased by adding 1.3 kg/m2 of salt to six different plant species: Avicennia germinans, Baccharis halimifolia, Batis maritima, Borrichia frutescens, Iva frutescens, and Spartina alterniflora. By performing a multiple species examination, stress responses were examined to determine if consistencies within and between plant type, ambient salinity conditions, and host plant species (among other criteria) existed, allowing for generalizations to be made about stress and herbivore interactions. Herbivore responses were determined by direct visual counts and indirect visual evidence of insects (e.g. galls, stem boring, and leaf mining). A metaanalysis was then performed on the data to determine the factors that may result in consistent responses to salt stress. No differences were found between insect feeding guilds. Herbivory increased in the presence of that added salt in high ambient salinity conditions, increased on experimental Spartina plants, and decreased on experimental Iva plants. These findings suggest that stress is generally a more important factor for plants in areas of already high ambient salinity. Results have been disparate in various studies, likely due to the difficulty in making comparisons between different field sites and experimental designs. This study addresses these issues, and ultimately finds that consistencies can be found among multiple species within communities.

Basigin gene products are cell adhesion molecules that are expressed by photoreceptor cells, Müller cells and endothelial cells of the mammalian retina. Previous studies have suggested that a lactate shuttle exists between the photoreceptor cells and the Müller cells, with Basigin being an essential component in this shuttle. Deletion of the Basigin gene in mice results in blindness with an eventual retinal degeneration. It was hypothesized that the lactate shuttle between photoreceptors and Müller cells does not form in Basigin null mice and that the blindness is attributed to faulty photoreceptor metabolism. Therefore, the purpose of this study was to determine whether the mitochondria of the Basigin null mice are metabolically active in the absence of the lactate shuttle. Mitochondrial health in the Basigin null mouse retina was assessed by a variety of assays, including ELISA analyses to measure Cytochrome c concentration and expression of autophagy-specific proteins. Mitotracker dyes were used to stain the mitochondria of Basigin null and normal retinas to determine the number of metabolically active mitochondria and the total number of mitochondria. The results showed that apoptosis and autophagy are not occurring in the Basigin null animals at a rate greater than that of the normal animals. The Mitotracker assay showed that there is a ~60% decrease in the total number of mitochondria in the null animals compared to their normal counterparts. A recalculation of the Cytochrome c assay in light of the reduced number of mitochondria in Basigin null mice revealed that apoptosis is likely occurring in these animals prior to the first signs of cytoarchitectural changes in the tissue. These results suggest that in the absence of the lactate shuttle in the Basigin null animals, the photoreceptors are unable to perform oxidative phosphorylation at the necessary rate, thus decreasing the number of mitochondria, which results in limited photoreceptor functionality, hence blindness.

Cyanobacteria are important components of the aquatic system, valued for their oxygen production, nitrogen fixation, and as the base of many aquatic food webs. This study investigated several aspects of cyanobacteria such as the diversity and response to nutrient enrichments. A survey of Northeast Florida was conducted between the years of 2010 and 2012; a total of 145 taxa were identified in freshwater habitats, such as springs, lakes, rivers, and retention ponds. While surveying the St. Johns River in Jacksonville, Florida, a novel Stigonematalean taxon was isolated and cultured. Subsequent morphological and genetic analyses indicate that this taxon is related to Fischerella, Nostochopsis, and Westelliopsis, though with poor bootstrap support. Thus, a new genus and species (Reptodigitus chapmanii gen. et sp. nov.) is proposed. Cyanobacterial community shifts are increasingly being employed as an indicator of ecosystem health. The last part of this study is an experimental manipulation of nutrients and subsequent community analyses. Chlorophyll a, total number of cells, and Dmax were significantly different between control groups and nutrient enriched groups. Phosphate was not strongly correlated to species richness, chlorophyll a, evenness, total number of cells, species richness, or diversity in either the control or the nutrient enriched groups. Nitrogen displayed similar results, though it was slightly more strongly correlated to evenness and diversity in the nutrient enriched group than the control group. The results of the survey and nutrient enrichment experiment are important parts of the investigation into how cyanobacterial communities respond to changes in nutrient concentrations, which can then be used to devise a standard metric against which water management agencies can compare to determine the health of a given aquatic system.

Seagrass meadows are essential to coastal ecosystems and have experienced declines in abundance due to a series of environmental stressors including elevated salinity and incidence of disease caused by the pathogen Labyrinthula sp. This thesis evaluated the dynamics between T. testudinum and Labyrinthula concerning the impacts of short term elevated salinity stress on the early stages of infection in Thalassia testudinum (Chapter 2) as well as the presence of anti-labyrinthulid secondary metabolites produced by the tropical seagrass (Chapter 3). The results showed that short term exposure to hypersalinity alters some cellular processes but does not necessarily lead to an immediate increase in wasting disease susceptibility. Specifically, the occurrence of disease was significantly lower in the hypersalinity treatments possibly due to a direct osmotic shock to Labyrinthula or indirectly due to the increase in in vivo H2O2 concentrations that may have inhibited Labyrinthula growth. In addition, it was shown that 4 phenolic acids commonly found in turtlegrass leaf tissue were able to inhibit Labyrinthula growth in culture. Using a bioassay-guided fractionation technique, several purified fractions of T. testudinum leaf tissue showed anti-labyrinthulid activity, however the detailed characterization of the unknown compounds was inconclusive. The results presented in this thesis highlight the halotolerant characteristics of the seagrass T. testudinum as well as suggest that T. testudinum has the capability of defending itself against Labyrinthula infection using secondary metabolites.