The Mississippi and Alabama barrier islands are sensitive landforms that are affected by hurricanes, longshore currents, and available sediment, yet these effects are difficult to quantify with traditional ground-based surveying. In this study, Landsat satellite imagery was used to evaluate changes in barrier island area and centroid position from 1990 and 2005. When hurricanes are infrequent (1999?2003), barrier islands generally increased in total area and showed only moderate repositioning of their centroid locations. However, when hurricanes were frequent (1994?1999 and 2004?2005), barrier islands showed substantial decreases in area and dramatic repositioning of their island centroid locations. This was especially true following Hurricane Katrina (2005). From 1990 to 2005, the general movement of barrier islands was westerly and most islands experienced an overall reduction in area (-18%). The results of this research are similar to findings reported in the literature and illustrate the suitability of using Landsat imagery to study geomorphic changes.

In the nutrient-poor soils characteristic of coastal environments, symbiotic association with the nitrogen-fixing root endosymbiont Frankia is essential to establishment and survival of the woody shrub Morella cerifera. Nutrient deficiency quickly becomes severe unless seedlings are infected by Frankia soon after germination. However, the means of arrival of Frankia prior to shrub establishment has not been determined. Using sterilized lab-grown M. cerifera seedlings and fecal samples collected from passerine birds on the Eastern Shore of Virginia, viability of avian dispersal of the bacteria was tested. Although passerine fecal samples did produce nodules on some sterilized M. cerifera seedlings, these experimental inoculations did not lead to significantly higher likelihood of nodulation, relative to sterilized reference seedlings. Non-sterilized seedlings displayed greatest percent nodulation; results suggest that passerines contribute to Frankia dispersal, but also that the actinomycete is contained on or within viable seeds or fruits of M. cerifera, and therefore may be co-dispersed directly from the parent plant.

Shrub expansion in herbaceous ecosystems is emerging as an important ecological response to global change, especially in mesic systems where increases in canopy biomass are greatest. Two consequences of woody encroachment are increases in belowground resources, such as carbon and nitrogen, and reductions in above-ground resources such as light, which affect diversity, community trajectory, and ecosystem function. My objective was to determine how expansion of the nitrogen-fixing shrub Morella cerifera affected the resource environment across a chronosequence of shrub expansion on a Virginia barrier island. I quantified changes in carbon (C) and nitrogen (N) cycling, canopy structure and understory light associated with M. cerifera expansion. Litterfall in shrub thickets exceeded litterfall for other woody communities in the same region, and due to high N concentration, resulted in a return of as much as 169 kg N ha-1 yr-1 to the soil, 70% of which was from symbiotic N fixation. Litter and soil C and N pools were 3-10 times higher in shrub thickets than in adjacent grasslands. Understory light in shrub thickets decreased to as low as 0.5% of above-canopy light. Sunflecks in shrub thickets were shorter, smaller and less intense than sunflecks in forest understories. However, relative to other shrub species such as Elaeagnus umbellata, M. cerifera was less efficient at intercepting light. Although M. cerifera had the highest leaf area index (LAI) of five shrub species studied, M. cerifera was relatively inefficient at light attenuation due to low levels of branching, steep leaf angles and a relatively shallow canopy. The shift from grassland to shrub thicket on barrier islands, and in other mesic systems, results in a significant change in canopy structure that alters understory resource availability and greatly alters ecosystem function and trajectory.

Trinity, East, and Wine Islands make up the eastern half of the Isles Dernieres barrier arc in south-central Louisiana. Formed following the abandonment of the Lafourche delta complex, subsidence and storm erosion have led to rapid deterioration of the system. Since 1887, the land area of the islands has decreased seventy-seven percent, and the gulf shoreline has retreated landward more than a kilometer. Wave ravinement on the shoreface of the islands is responsible for the most sediment loss; liberated sediment travels longshore to tidal inlets. The dominant ebb tidal currents then transport the sediment to where it is deposited in ebb tidal deltas or carried to the west, out of the system. A large lobe of sediment bypassing Cat Island Pass is entering the system from the eastern lower shoreface, which helps replace some of the sediment lost through wave ravinement to the upper shoreface.

Tidal inlets play a significant role in barrier island sustainability along the barrier islands of southern Louisiana. With increasing tidal prism, major changes are taking place within and adjacent to the inlets. The purpose of this thesis is to examine how Caminada Pass, a tidal inlet along the Caminada-Moreau headland, has evolved through time. Fundamental to this effort is evaluating which processes have contributed toward inlet evolution and what is the response of the inlet-bordering barrier island shorelines of Grand Isle and Elmer’s Island. This effort summarizes previous results and utilizes published bathymetric data, aerial photographs, vector shorelines, satellite images, and seafloor grab samples. The intent of this research is to document the variety of data that are available for future studies of Caminada Pass, an evaluation of long and short-term changes to the system, and an overall better understanding of the inlet dynamics of Caminada Pass.

The southern Chandeleur Islands are an ideal setting to study shoal evolution given their history of submergence and re-emergence. Here, numerical models shed light on the attendant processes contributing to shoal recovery/reemergence following a destructive storm event. Simulations of a synthetic winter storm along a cross-shore profile using Xbeach shows that convergence of wave-induced sediment transport associated with repeated passage of cold-fronts initiates aggradation, but does not lead to reemergence. A Delft3d model of the entire island chain shows that as these landforms aggrade alongshore processes driven by incident wave refraction on the shoal platform, backbarrier circulation and resulting transport become increasingly important for continued aggradation and eventual emergence. Aggradation magnitudes are a function of depth ranging from 2 – 10 mm per event (onset to recovery to near mean sea level). In the absence of big storms, this modest aggradation can be more than one meter in a few years.

The alongshore variability of beach-dune systems and the response and recovery from extreme storms remains poorly understood. The height and extent of foredunes along barrier islands varies over a range of spatial scales, implying that during extreme storms, the beach-dune system should respond in different ways depending on the elevation and volume of the dunes relative to the storm surge. The purpose of this study is to use Ground-Penetrating Radar (GPR) and vibra-cores to investigate the internal structure of small, intermediate and large dunes along a 2.5 km transect of beach in Padre Island National Seashore, TX with particular attention to storm impacts. A series of dune normal and parallel GPR profiles were collected to capture the variation in beach-dune morphology at the three sites. Site locations were chosen along a transition from dissipative to intermediate beach states. Following the Sallenger (2000) storm impact model, the small dune is defined by low-lying topography that is susceptible to overwash and inundation depending on the size of the storm surge. The large dune is characteristic of the “collision regime”, while the intermediate dune represents a transition between “overwash” and “collision regimes”, with the underlying assumption that all three dunes would be impacted by the same level of surge during a single storm event. Results from the GPR survey suggest that each site contains a bright, laterally continuous radar reflector that is interpreted with the aid of the sedimentary data as an erosional layer. Different characteristic radar facies and sequence boundaries provide evidence as to how each dune evolved through and after the storm. Results from XRF scans and grain size analysis show a direct comparison between the GPR reflectors at the storm surface and spikes in calcium counts from XRF scans to distinct changes in grain size parameters at the same depth. It is argued that the location of each shell layer corresponds to a storm surface generated during a single storm, which means it is possible to interpret different recovery mechanisms. The presence of the storm layer across the backbeach and dunes provides evidence for the height and extent of the surge during the storm event. The data suggests that the small dune was overtopped by the surge, experiencing minimal erosion and recovery. The intermediate dune was completely eroded by the surge, but showed the greatest recovery of all the dune sites. The large dune was scoured at the base with marginal impact along its crest and shows minimal recovery after the storm. These results suggest that the evolution (i.e., transgression) of a barrier island varies considerably over short distances.

Thesis (M.S.)--University of North Carolina at Wilmington, 2004. / Includes bibliographical references (leaves : [92]-97).

Barrier islands are dynamic environments facing increasing vulnerability to climate changes, sea level rises, and anthropogenic activities. Hurricane Sandy (October 2012) modified the Atlantic coast of the United States. On Fire Island and Westhampton Island, New York, multiple overwashes and three breaches occurred. The U.S. Army Corps of Engineers filled two breaches, increased dune elevation and stabilized dunes by planting American beachgrass (Ammophila breviligulata). They built two restoration areas to mitigate the impact of an island stabilization project to federally listed breeding piping plovers (Charadrius melodus). The goal of this thesis was to quantify habitat changes after Hurricane Sandy, and assess habitat use of piping plovers specifically in human-created restoration areas. We created land cover maps using an object-based classification method (overall accuracy 85%), and field-collected data from four post-hurricane habitat types. Vegetation cover increased across all habitat types, especially in manipulated (30.1% increase) and natural overwashes (37.9% increase), while dry sand for nesting declined by 8%. Vegetation density indices were higher in natural overwashes than planted engineered dunes, likely a reflection of plant age and establishment. We monitored 83 nests (67 pairs) of piping plovers from 2015–2017. Restoration areas were successful in attracting breeding piping plovers, although pair densities were lowest in this habitat in 2016, and in 2017 plovers selected against the restoration areas (�2 = 29.47, df = 3, p<0.0001). There was no effect of habitat type on reproductive parameters. We suggest vegetation removal may be necessary to maintain early successional habitats for piping plover management. / Master of Science / Barrier islands are thin strips of land, which generally lie parallel to the mainland. They are dynamic environments subject to change from weather conditions and ocean currents. They are vulnerable to future climate changes, sea level rise, and increased human activity. Hurricane Sandy, October 2012, caused major landscape changes to the Atlantic coast. On two barrier islands, Fire Island and Westhampton Island, south of Long Island, the U.S. Army Corps of Engineers (USACE) further modified the post-hurricane habitats. They created two restoration sites designed to offset the impact of an island stabilization project to a federally protected breeding shorebird, the piping plover. Piping plovers nest on unvegetated or sparsely vegetated sand. We created land cover maps from aerial images and collected field data to describe habitat changes after Hurricane Sandy (2013, 2015–2017) in four habitat types creating during or after the hurricane. The vegetation cover and density increased across these four habitats, but especially in the manipulated overwashes and natural overwashes. This is likely due to the age of the plants in each habitat type. As vegetation grew back, areas of sand in each habitat type declined. Human-created restoration sites were used by plovers but in 2017 plovers used them less than expected. We monitored piping plover nests and chicks (April to August 2015–2017), and there were no differences in these measurements among habitat types. The findings from this thesis will assist in piping plover conservation on Fire Island and Westhampton Island.

Stability of coastal systems are threatened by oceanic and atmospheric drivers of climate change. Sea-level rise compounded with increased frequency and intensity of storms emphasizes need for protection of inner island systems by dune formations. Dune building processes are affected by interactions between growth of ecosystem engineering dune grasses and environmental factors associated with disturbance such as sand burial and salt spray. Climate change may also cause latitudinal expansion of some species, resulting in emergence of competitive interactions that were previously absent. Topographic structure of coastlines, traditionally influenced by sand burial, could change as a result of competition emergence. My goal was to determine if species functional trait responses to common abiotic factors are altered by novel and current biotic interactions. I performed a multi-factorial greenhouse experiment by planting three common dune grasses (Ammophila breviligulata, Uniola paniculata, and Spartina patens) in different biotic combinations, using sand burial and salt spray as abiotic stressors. I hypothesized that biotic interactions will cause these dune grasses to shift functional trait responses to abiotic factors that are associated with dune building. I found that plants consistently decreased in biomass when buried. I also found that competition between A. breviligulata and U. paniculata negatively affected dune building function traits of A. breviligulata. This indicates that competition with U. paniculata could alter dune structure. In comparison A. breviligulata had a positive interaction with S. patens, which increased functional trait responses to abiotic stress. Last, we found that competitive intransitivity could occur between these species. My results can be used to make predictions on cross-scale consequences of novel competitive events. This experiment also provides evidence that consideration of local biotic interactions is important in understanding connections between plant level dynamics and large-scale landscape patterns in high stress environment.