Results of past studies on the spring-fed salt marshes of Utah indicated that waterfowl production on these areas was much lower than on Utah's river-fed marshes. Waterfowl production on the newly-established Fish Springs National Wildlife Refuge, a spring-fed marsh, increased considerably, however, after its waters were impounded. It was believed that by determining what caused this increased production at Fish Springs it would be possible to obtain greater waterfowl production a t other spring-fed marshes. Consequently waterfowl populations and factors affecting waterfowl production on this marsh were studied during the summers of 1966, 1967, and 1968. Populations of breeding ducks averaged approximately 900 pairs a year in 1967 and 1968. Mallards, cinnamon teal, and redheads comprised about 80 percent of these birds. Nesting densities, on plots representing available habitat, averaged about one nest per acre during these two years. In 1967 and 1968 a total of 312 duck nests representing 10 species were studied and their fates determined. Overall nest success was 63 percent, and predators, principally coyotes and striped skunks, destroyed 25 percent of all nests. Calculated duckling mortality rates during 1967 and 1968, respectively, were 19 and 16 percent. Duck production at Fish Springs averaged about 3,000 birds or about 430 ducks per square mile of marsh habitat a year during this period. At present the sparsity of adequate nesting cover for gadwalls appears to be an important limitation to breeding by this species at Fish Springs. Nesting cover apparently has not limited the use of this marsh by other waterfowl species, however, as evidenced by a high incidence (76 percent) of nesting on dry ground by redheads and ruddy ducks. Aquatic insect sampling in waters inundating portions of the original Fish Springs marsh indicated that these waters produced large quantities of proteinaceous foods for ducklings. Populations of aquatic insects in the original marsh were probably low except in recently disturbed areas. It appears that limitations of brood-rearing habitat were primarily responsible for low waterfowl production in the past. Newly-created impoundments, rich in animal food, were probably the key to the increase in waterfowl production on this marsh.

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Rates of marsh wetland loss in the northern Gulf of Mexico are the highest observed in North America. Marsh terraces have been implemented over the last 30 years to address this loss. Marsh Terraces reduce fetch and resulting wave energy which, reduces rates erosion of sediments in coastal wetlands. This thesis evaluated marsh terraces by extensive data collection that will assess the spatiotemporal relationships between wind patterns, wave parameters, and sediment strength in water bodies modified with marsh terraces. Data collected during two four-month deployments captured the passage of 40 cold front storms and the passage of Hurricane Barry. Results indicated that the mean threshold for erosion for marsh platform and terraces (0.194 N/m2 and 0.500 N/m2) were often exceeded during the passage of cold front storms. Orientation to reduce the influence of these storms was determined to be 270/55 which is perpendicular to cold front associated winds.

<p> Wetlands are a valuable resource, providing many ecosystem services, but unfortunately, coastal wetlands in the Great lakes are under threat from human development, including water quality impairment, introduction of exotic invasive species as well as physical damage such as dredging, draining, and filling in of wetland habitat. These actions have a negative impact on the native flora and fauna in wetlands, making wetland conservation and important topic. </p> <p> Wetland macrophytes play a vital role within wetlands, not only providing food for water fowl, migratory birds, fish, and mammals, but also providing the physical structure that is necessary for fish spawning, and they provide habitat for macroinvertebrates and zoobenthos. Different macrophyte species have been found to be associated with varying water quality conditions, and because of this wetland macrophytes are useful indicators of water quality conditions. I have developed a Wetland Macrophyte Index (WMI) using 127 wetlands throughout all five Great Lakes (Chapter 1 ), which relates plant species presence/absence data to water quality conditions, making it a useful indicator of fish habitat. The WMI was validated using historical data from two wetlands from before and after a remedial action plan was put in place and also it was successfully applied to two Canadian National Parks. </p> <p> Information on the presence/absence of wetland macrophytes can be a very important tool in wetland conservation, but, unfortunately, there is no standard method for sampling macrophytes. In the second chapter I will compare two common macrophyte sampling methods (grid and transect) to a novel method (stratified) in six wetlands (three pristine and three degraded). The stratified method has proven to be beneficial for determining the macrophyte biodiversity within a wetland because more species, more unique species, and more rare species were found with the stratified method compared to the grid and transect methods. </p> / Thesis / Master of Science (MSc)

This thesis examines the relationships between rising water levels, vulnerable land, and sedimentation within the Chesapeake Bay watershed. Climate induced sea level rise threatens low lying coastal land, especially in regions of continuing subsidence such as the Chesapeake Bay. Alterations to shorelines over time have impacted the ability of coastal landscapes to capture and build up sediment, exposing them to continual erosion. The low lying neighborhood of Belle View along the Potomac River is the focus of the investigation due to its vulnerability to flooding and its cultural and ecological connections to the adjacent landscapes of Dyke Marsh and the George Washington Memorial Parkway. Through careful placement of breakwater infrastructure, sediment will build over time as the water rises, mitigating the effects of coastal flooding in this region. Alterations to the landscapes of the marsh and parkway allow for their cultural and recreational values to be strengthened over time as the landscape adjusts to the rising sea level. / Master of Landscape Architecture / Climate change, or the belief that human activity is altering the earth's climate, is projected to increase the occurrence of flood events due to water levels rising over time from glaciers melting. Previously, shorelines have been hardened with levee or seawall infrastructure to creates a barrier between the water and developed land. Hardened shorelines may increase water velocity and reflect wave energy in riverine landscapes, consequentially disturbing natural shorelines. This disturbance leads to the gradual loss of sediment over time and therefore a loss of ground elevation. When landscapes lose elevation, they become more vulnerable to rising water levels and flooding. This relationships between shoreline types, sedimentation, rising water, and vulnerability inspired me to discover and design a threatened landscape that would capture sediment within the river's water column to build elevation over time and protect the adjacent development from rising water. The area encompassing the low lying neighborhood of Belle View, Dyke Marsh, and the George Washington Memorial Parkway along the Potomac River is the focus of the investigation due to its vulnerability to flooding. With a careful understanding of sediment capture infrastructure dynamics, the design introduces breakwaters on the site to allow sediment to build over time as the water rises. This research and design thesis demonstrates a strategy to create landscapes that will evolve over time to mitigate future flooding events and create more resilient landscapes.

Recycled glass cullet is a potential alternative to fill substrate in salt marsh restoration projects, given its similarity to natural silica sands. However, the ability for common salt marsh plants to grow in glass cullet has not yet been tested. An outdoor mesocosm experiment assessed the ability of the dominant mid-marsh plant Juncus roemerianus and the upland marsh plant Spartina patens to grow in various mixtures of glass cullet versus fill soil. Results showed that J. roemerianus can survive in glass cullet, but growth declined as the proportion of cullet increased. However, S. patens grew comparably, if not better, in treatments up to 75% glass cullet. In the face of increased coastal land loss and a global sediment deficit, the use of glass cullet in upland salt marsh restoration projects can simultaneously divert glass from landfills and promote more sustainable coastal restoration strategies along the northern Gulf of Mexico.

Appreciation of the ecological and economic values associated with healthy salt marshes has led to a recent rise in the number of marshes that are being targeted for restoration by dike removal. The success of restoration is often measured by the return of marsh plants, though this overlooks a key component of salt marshes, that of the invertebrate community within marsh sediments. To evaluate the short-term recovery of these invertebrates, sediment cores were collected across an elevational gradient in a recent dike removal marsh, one and two years post removal, and a nearby reference marsh. Abundance, richness and diversity as well as morphospecies community composition were compared across treatment groups (Reference, Removal) and elevation zone (High Marsh, Low Marsh). Morphospecies richness, abundance and diversity were significantly higher in Low Marsh samples than in High Marsh samples, though no statistically significant differences were found across treatments of the same elevation (e.g., Reference Low Marsh versus Removal Low Marsh). Pair-wise ANOSIM results found significant differences between community compositions across treatments, specifically Reference Low Marsh and Removal Low Marsh. The marsh edge, the lowest point of vascular plant growth before transitioning to tide flats, is considered a high stress environment for emergent vegetation. Plant establishment and survival in this low elevation zone is limited by the tolerance to inundation duration and frequency and anoxic sediments. Bioturbation and burrowing by macroinvertebrates increases the surface area exposed to surface water for gas exchange, increasing the depth of the redox potential discontinuity layer. Crabs that make stable, maintained burrows have been shown to increase oxygen penetration into sediment, improving plant productivity. Such crabs are not found in salt marshes of the Pacific Northwest of North America. However, other burrowing invertebrates may have a positive impact on plant health in these areas by reducing abiotic stress due to anoxic sediments, thereby allowing plants to establish and survive lower in the intertidal zone. To assess this potential relationship, study plots of Distichlis spicata were selected at equivalent elevations at the lowest point of plant establishment at the marsh edge. Focal plant rhizomes were severed from upland ramets and assigned an invertebrate abundance treatment based on a visual burrow count surrounding each plant (9 cm diameter). Focal plants were visited monthly from July to September 2016, plant health variables of chlorophyll content and chlorophyll fluorescence (photosynthetic efficiency), and sediment ORP readings were collected. Plant survivorship was significantly higher in plots with invertebrates, 96% of plants in 'With Invertebrate' plots and 50% of plants in 'No Invertebrates' plots survived the duration of the study. Plant health (chlorophyll content and chlorophyll fluorescence) generally increased with increased invertebrate presence though, not statistically significant. There may be potential for improved plant productivity and resilience to plants at the marsh edge due to invertebrate burrowing activity. This benefit could help mitigate projected losses in plant productivity due to sea level rise, though more research is needed to investigate the mechanism by which these invertebrates confer a health benefit to plants at the marsh edge.

Herbivores and pathogens pose a consistent threat to plant productivity. In response, plants invest in structural and/or chemical defenses that minimize damage caused by these biotic stressors. In salt marshes along the Atlantic coast of the United States, a facultative mutualism between snails (Littoraria irrorata) and multiple species of fungi exert intense top-down control of the foundation grass species Spartina alterniflora. Since exposure to herbivores and pathogens are tightly coupled in this system, I investigated whether S. alterniflora utilizes chemical and/or structural defenses to deter both snails and fungi, and examined how plant defenses varied among S. alterniflora individuals and populations. I also assessed how other marsh plants prevent snails from establishing farms, and considered whether interspecific variation in plant chemical defenses influences marsh community structure. Initial experiments revealed that S. alterniflora chemical defenses inhibited L. irrorata and two fungi that snails commonly farm. A caging experiment determined that production of chemical defenses could not be induced in the presence of snails and fungi, nor relaxed in their absence. Through separations chemistry guided by ecological assays, I isolated two distinct classes of chemical defenses from short form S. alterniflora, one of which inhibited fungal growth and the other decreased plant palatability. In a community context, the chemical defenses produced by S. alterniflora were relatively weak compared to those of four other salt marsh plant species, which produced compounds that completely inhibited L. irrorata grazing and strongly hindered fungal growth in lab assays. Nutritional and structural differences among marsh plants did not influence feeding preferences, suggesting that plant secondary chemistry was the primary driver for food selection by snails. It appears that S. alterniflora produces weak chemical defenses that slow down or limit fungal growth and snail herbivory, and may compensate for tissue losses by producing new growth. In contrast, less abundant marsh plants express chemical defenses that completely inhibit fungal farming and deter snail grazing, but doing so may come at a cost to growth or competitive ability. As marsh dieback continues with rising herbivore densities and compounding abiotic stressors, the ecosystem services that salt marshes provide may be lost. Therefore, understanding how and under what conditions salt marsh plants resist losses to herbivores and pathogens will help predict which marsh communities are most likely to be threatened in the future. Initial experiments revealed that S. alterniflora chemical defenses inhibited L. irrorata and two fungi that snails commonly farm. A caging experiment determined that production of chemical defenses could not be induced in the presence of snails and fungi, nor relaxed in their absence. Through separations chemistry guided by ecological assays, I isolated two distinct classes of chemical defenses from short form S. alterniflora, one of which inhibited fungal growth and the other decreased plant palatability. In a community context, the chemical defenses produced by S. alterniflora were relatively weak compared to those of four other salt marsh plant species, which produced compounds that completely inhibited L. irrorata grazing and strongly hindered fungal growth in lab assays. Nutritional and structural differences among marsh plants did not influence feeding preferences, suggesting that differences in plant chemistry were the primary driver for food selection by snails. It appears that S. alterniflora produces weak chemical defenses that slow down or limit fungal growth and snail herbivory, and may compensate for tissue losses by producing new growth. In contrast, less abundant marsh plants express chemical defenses that completely inhibit fungal farming and deter snail grazing, but doing so may come at a cost to growth or competitive ability against S. alterniflora. As marsh dieback continues with rising herbivore densities and compounding abiotic stressors, the ecosystem services that salt marshes provide may be lost. Therefore, understanding how and under what conditions salt marsh plants resist losses to herbivores and pathogens will help predict which marsh communities are most likely to be threatened in the future.

The ability of prey to detect and respond appropriately to predator risk is important to overall prey fitness. Many aquatic organisms assess risk through the use of chemical cues that can change with predator diet. Two variable characteristics of diet are: 1. prey type and 2. prey mass. To assess the effect of these two characteristics on the assessment of risk by the mud crab Panopeus herbstii, I exposed mud crabs to the urine of the blue crab Callinectes sapidus fed one of 5 diet treatments: 10g of oyster shell free wet mass, 5g of oyster shell free wet mass, 10g crushed mud crabs, 5g crushed mud crabs, and a mix of 5g of oyster shell free wet mass and 5g crushed mud crab. Effects on P. herbstii foraging were tested in a previously developed bioassay by measuring shrimp consumption over a 4 hour period. I hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a diet of crushed mud crabs than to urine from C. sapidus fed a diet of oysters. I further hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a high mass diet relative to a lower mass diet. Contrary to expectations there was no observed effect of urine on P. herbstii foraging in any of the treatments. Results suggest that bioassay protocol may be unreliable suggesting further replication to determine the difference between this study and previous results. Future studies examining how P. herbstii varies with urine concentration will aid in understanding the ecological scale of this predator cue system. Determining the role of other potential cue sources will improve the predictive abilities of these studies.

No description available.