Coastal habitats provide invaluable economic and ecosystem services. However, coastlines are eroding at increasing rates due to anthropogenic and climate driven changes. Grey and green infrastructure solutions have been proposed to retard the decay of coastlines, with oysters serving as a popular living shoreline. Three community-based stabilizations that implemented living shorelines and engaged local communities in restoration efforts over the past decade in Volusia County were revisited to determine if they were successful and if they produced positive public perceptions of success. Chicken Island, which was restored after waves, boat wakes, tides, and adverse weather altered the natural shoreline, had significant increases in oyster size and density but an unsuccessful deployment of mangrove seedlings. The Port Orange study site installed living shoreline along existing sea wall and experienced low oyster recruitment, limited success with S. alterniflora propagation, and high cover of bare sediment. The Mosquito Lagoon Marine Enhancement Center had high vegetative cover and biodiversity and decreases in oyster density likely due to the development of healthy, mature oyster reefs. A survey of volunteers who participated in these three restoration projects was also conducted to determine if there is a tie in ecosystem function produced through restoration and community perceptions of restoration success. While there were not enough survey responses to draw conclusions, the responses were indicative of the future research needed to understand volunteer identities and sense of place as they relate to the human-nature system. To improve the long-term success of living shorelines, it is critical to not only select restoration methods appropriate for the specific location of the restoration, but to involve local communities to increase sense of self and investment in restoration efforts.

Animals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They generate simple, stereotyped mate attraction signals that are easy to record and quantify, and that are well-understood from the neurobiological perspective. Additionally, they live in electrically-crowded environments, where multiple congeners live and reproduce in close proximity. This dissertation reports an investigation of electric signal diversity and reproductive life history in a nine-species assemblage of the electric fish genus Brachyhypopomus from the upper Amazon. A year-long quantitative sampling program yielded a library of electric signal recordings from >3,000 individuals and an accompanying collection of preserved specimens from which suites of informative life history traits were measured. These data were used to understand basic reproductive biology, and to describe sexually dimorphic and interspecific diversity in electric signals. By integrating approaches from ecology, physiology, and evolutionary biology, novel perspectives are provided on: 1. how sexual selection and species recognition interact to shape signal diversity and the occupation of signal space in multi-species animal communities; 2. how extreme seasonal variation in Amazonian ecosystems influences trade-offs in the allocation of reproductive resources – including mate attraction signals, and; 3. how environmental variation shapes general life-history traits in a diverse tropical animal assemblage.

There is a universal consensus that global sea levels will rise at an increased rate from those in the recent past. Rising seas will dramatically increase the vulnerability of coastal communities and ecosystems. Tidal marshes are considered to be among the most valuable and vulnerable ecosystems in the world. The effects of sea-level rise (SLR) on tidal marshes are diverse, comprising changes in tidal amplitude and flow patterns, changes in sediment transport, shoreline erosion, changes in salinity gradients, landward migration of tidal habitats, variations in species composition, and habitat loss. There is an increasing concern over how accelerated rates of SLR will impact tidal marsh ecosystems. Many marshes will likely cross thresholds and experience significant and irreversible changes, such as marsh fragmentation and total disintegration due to erosion or drowning. The response of marshes to SLR is expected to vary based on different geomorphic settings, hydrodynamics, sediment sources, and anthropogenic stressors. Due to the increased need to assess tidal marsh vulnerability in the light of changing environments, different models have been developed to predict marsh spatial extent and future distribution. Current models are constrained by the limitations of the two modeling approaches: landscape-scale models and site-specific models. Despite the progress in evaluating marsh response under the effect of SLR, significant challenges still remain in simulating cross-scale processes related to marsh establishment and persistence. This dissertation presents a new approach to modeling marsh evolution. The Tidal Marsh Model (TMM) has been developed as a module within the SCHISM framework (Semi-implicit Cross-scale Hydroscience Integrated System Model). The TMM has unique features (e.g. dynamic rates, cross-scale simulations, and incorporation of anthropogenic stressors) that allow it to overcome many limitations that current marsh models possess. The study areas considered in this study (Carter Creek and Taskinas Creek, Virginia, USA) are representatives of other marsh systems found throughout the Chesapeake Bay and its tributaries. Marshes in these areas are associated with different geomorphic settings, hydrodynamics, and anthropogenic stressors. These study sites were the focus for model development and calibration, model upgrade, and applications. The TMM simulates marsh migration under the joint influence of tides, wind waves, sediment transport, shoreline structures, land use, and precipitation. The evaluation of model performance was conducted via hindacat (past 40 years). Marsh change was captured with an accuracy of 81% in Carter Creek, and an accuracy of 78% in Taskinas Creek. To refine the initial version of the model, a vegetation algorithm was developed within the TMM code, which accounts for the effects of vegetation on the nearshore hydrodynamics. This new functionality contributes to an improved understanding of how marsh plants affect the mean flow velocity and turbulence, and consequently, the sedimentation processes. The TMM was applied in the two study areas to forecast the potential impacts of SLR on marsh sustainability. Using two SLR scenarios, changes in marsh extent and distribution were projected over the next 50 years. Model outputs offer detailed information about potential areas of marsh loss, as well as identify lands where marshes might have the opportunity to transgress and persist under the effect of SLR. This innovative approach provides coastal managers and decision-makers with valuable and necessary information for monitoring activities, restoration, and strategic planning to support marsh sustainability in a changing system.

Stressful environments can commonly be found at the edge of a species range and may be a driver for adaption in suboptimal environments. Furthermore, the edge of a species' range can expand and contract over time, resulting in multiple independent invasions of the same stressful habitat. Elucidating population genetic structure and demographic history can aid in determining the which geologic factors impact range distributions and when climatic changes occurred driving genetic patterns observed in contemporary populations. Moreover, populations at the edge of the species range may adapt to the stressful environments that occur at the range edge and exhibit genetic traits divergent from populations in the core of the species range. In this dissertation, I first examined how a stressor (salinity) has impacted genetic structure and demographic history in a wide-ranging, large semi-aquatic species, the American alligator (Alligator mississippiensis; Chapter 2). I estimated the splitting of genetic clusters and matched them with geologic events of past sea level rise. Then, I tested if coastal populations respond differently to changes in salinity compared to alligators from inland populations (Chapter 3). To do this I randomly placed juvenile alligators from coastal and inland populations in one of three salinities (0, 10, or 20 ppt) for two weeks. I collected behavioral, physiological, and histological datasets and found a habitat by salinity interaction with coastal alligators exhibiting a pattern of increased plasticity relative to inland alligators. In Chapter 4, I hypothesized that coastal and inland alligators would exhibit differentially expressed genes in osmoregulatory organs in response to salt stress. My data supported this hypothesis, and I found that the most differentially expressed genes functioned in signal transduction, metabolic pathways, and secretion. In addition, I found that at high salinities, coastal alligators upregulated genes coding for solute carriers compared to inland alligators. Overall, my dissertation contributed to the study of adaptive evolution by demonstrating that salinity has been a past and current stressor for American alligators. High salinity levels continue to limit the alligator's species range and lead to genetic differentiation among historically isolated regions. Yet, at the same time, I found evidence that coastal populations exhibit incipient adaptation to high salt environments. The patterns I found here are similar to other species that inhabit both freshwater and saltwater environments. As there appears to be evidence of convergent evolution for mechanisms to excrete salt in fully marine reptiles, my dissertation is starting to provide evidence for patterns of convergent evolution among reptiles that similarly use both freshwater and brackish water environments.

No description available.

No description available.

No description available.

The Asian clam, Corbicula fluminea, is one of the most invasive bivalves in the world but there is limited research on its presence in tidal freshwater systems. Despite its introduction into Chesapeake Bay tributaries in the 1970s, the initial colonization and subsequent development of populations of C. fluminea in the Mattaponi and Pamunkey sub-tributaries of the York River, Virginia, is mostly undocumented. This study assessed the spatial distribution and population structure of C. fluminea in tidal freshwater sections of these rivers (~45km) with benthic surveys during summer 2011 – 2012. Benthic grabs (2.4L, 0.023m2) taken at 40 sites in each river were analyzed for clam abundance and size. In addition, relationships between abiotic factors and clam distribution within each river were evaluated using Akaike’s Information Criterion (AIC) to compare a set of generalized linear models. C. fluminea was present at the majority of sites in both rivers during both years, with mean densities (m-2) during 2011 and 2012 of 660 and 410 for Mattaponi River; 1,451 and 834 for Pamunkey River. Populations were dominated by > 90% juvenile clams (< 6mm shell length), which is common for C. fluminea populations during recruitment periods. Both rivers had lower abundance during 2012, suggesting that C. fluminea is actively reproducing but not necessarily accumulating in the system. High juvenile and adult mortality are characteristic of C. fluminea populations. Compared to other invaded systems, C. fluminea in Mattaponi and Pamunkey Rivers is a low-to-moderate level invasion based on clam density. Using AIC analysis, the bestsupported models included factors of distance upriver (km), % sand, depth (m), and year. Distance and % sand showed positive relationships with C. fluminea abundance and had significant parameter estimates in all models (" = 0.05). Spatial analysis in GIS showed 3 that C. fluminea was widely distributed throughout the rivers but achieved higher densities further upriver and in sandier habitats. Despite these trends, Corbicula densities were highly variable, highlighting eurytopic habitat preferences of this species that have led to its successful invasion of tidal freshwater habitats. Populations may also be controlled by the high degree of physical disturbance in tidal freshwater systems and predation by fish and waterfowl.

Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals of toxicological concern present in humans, wildlife, and the environment. Deca-BDE is the highest production product due to historical use patterns and recent regulatory limitations on the other two commercial formulations (Penta-BDE and Octa-BDE) in the U.S and Europe. The EU banned Deca-BDE starting July 1, 2008. However, it remains in usage in North America and elsewhere in the world. BDE-209 is the dominant congener in all Deca- BDE commercial products. BDE-209 has been reported to under go metabolic debromination to lesser brominated and more toxic and bioaccumulative congeners. However, insufficient data are available on this process. It has also been observed that congener profiles and BDE-209 levels in terrestrial organisms differ from most aquatic species, indicating accumulation or metabolic dissimilarity. The goal of this in ovo study is to determine the biotransformation and tissue distribution of BDE-209 after injection into the yolk-sac of embryonic chickens. An emulsion formulation was employed to better distribute the hydrophobic BDE-209 within the eggs in an attempt to better mimic “natural” exposure of embryos. Acute mortality from BDE-209 yolk injection was observed. An LD50 value of 44 μg/egg (740 ng/g ww) was determined for embryonic chickens in this study. Concentrations of BDE-209 and possible metabolic degradates were determined in five compartments of the embryos (yolk, brain, liver, heart and remaining carcass). The results indicated that some BDE-209 was mobilized from the yolk, into the carcass, liver, brain, and heart tissues of the developing chicken embryo prior to pipping. However, 80% of the dose was detected as BDE-209 in the yolk sac. Additional BDE-209 would likely have been assimilated following hatching and resorption of the remaining yolk. Nona-BDEs were detected in all of the liver and yolk samples from BDE-209 exposed eggs. The congener profiles of the different tissues did not indicate that significant metabolic debromination of BDE-209 occurred within the developing embryos.

The studies involved in this thesis expanded the current project being conducted in Dr. Newman’s laboratory that aimed to define and quantify the impacts of mercury movement in contaminated aquatic and terrestrial food webs in the South River watershed (Virginia, USA). This expansion involved a two phase study, which fulfilled the requirement of a master thesis. Previous research in our lab documented mercury biomagnification in the river itself and two floodplain locations on the South River watershed. Predictive models were built for mercury concentration in members of these food webs. These studies reached a preliminary conclusion that mercury biomagnification in members of floodplain food webs was faster than that of the aquatic food web. To substantiate this finding and further understand the factors that might produce the differences observed among floodplain locations, two additional floodplain locations were sampled and modeled in 2010. Overall, the models constructed in this study for predicting methylmercury were superior to models for total mercury or the percentage of the mercury present as methylmercury. Including previous models for other sites, four of five attempted methylmercury models based on δ15N met the criterion for useful prediction. For the floodplain models, thermoregulatory strategy was found to have substantial influence on mercury concentrations of food web members. The food web biomagnification factors for the four floodplain locations were consistently higher than that of the contiguous aquatic food web. The second phase of this research focused on description and determination of current mercury exposure to adults of three avian species during nesting on the South River floodplain and judgment of the risk of harmful mercury exposure to these species by comparing the mercury exposure distributions to published toxicity test results. This study incorporated a formal expert elicitation involving a modified Delphi framework and a Monte Carlo simulation to accomplish a probabilistic risk assessment. Simulations from this study predicted the probability that an adult bird during breeding season would ingest harmful amounts of mercury during daily foraging and also the probability that the average mercury ingestion rate for the breeding season of an adult bird would exceed published rates found to cause harm to other birds (>100 ng total Hg/g body weight per day).The probabilities that these species’ averaged ingestion rates exceeded the threshold value were all less than 0.01.