Salt marshes are coastal wetlands that are highly productive and biologically diverse ecosystems. These systems are under threat from rising sea levels which are predicted to accelerate in the future. Salt marsh habitats of the Swartkops, Kromme and Knysna estuaries were examined to determine their structure along an elevation gradient and how this structure has changed over the past six decades, what the primary drivers of this structure were and whether the salt marsh surface is stable, rising or declining relative to predicted sea level rise. During this study the following main hypothesis was tested: The environmental drivers of salt marsh zonation are elevation above mean sea level (AMSL), soil moisture and soil salinity, all of which will be impacted by the predicted rise in sea level of 1.48 mm.y-1, unless the salt marshes are able to accrete at a rate such that surface elevation gain is sufficient to offset the rate of sea level rise. The results showed that the salt marsh vegetation structure followed a predictable pattern down the elevation gradient with distinct supratidal, intertidal and subtidal habitats identified for each estuary. These three zones occurred between elevations around Mean Sea Level of -0.86 to 2.42 AMSL for Swartkops, -0.3 to 2.95 m AMSL for Kromme and -0.48 to 3.14 m AMSL for Knysna. A floodplain component was also identified in the Swartkops estuary, which was restricted to the upper reaches. During the last 60 years, losses of intertidal and supratidal salt marsh for Swartkops were 74.31 ha and 30.23 ha respectively, 17.01 ha of intertidal and supratidal salt marsh was lost in Kromme while intertidal salt marsh in Knysna has diminished by 168 ha. These losses were mainly attributed to developmental pressure, although there are indications that rising sea levels are becoming more influential in the lower reaches. The main environmental drivers for salt marsh structure in the Swartkops were shown to be soil moisture content and elevation, soil moisture and organic content for Kromme while elevation and soil redox potential were dominant in Knysna. In a comparison of all three systems, soil moisture content and redox potential were found to be the most important drivers of vegetation distribution. Elevation dictates tidal inundation periodicity and frequency, and thus acts to influence all edaphic factors driving vegetation distribution. Results indicated that the salt marsh surface elevation of the lower and middle sections of the Swartkops, Kromme and Knysna estuaries are generally declining relative to current sea level rise. Where increases in surface elevation (relative to current sea level rise) were recorded, the majority of the accretion occurred after episodic flooding in winter 2011. These increases typically occurred in the upper reaches and were attributed to the deposition of fluvial sediments as a result of these floods. Results for Knysna indicate that while a majority of the salt marsh surface is accreting vertically, only three areas are increasing their elevation at a rate at least equal to current sea level rise. In these areas, developmental pressures will prevent a landward transgression of the salt marsh, forming an artificial “coastal squeeze”. Geomorphological limitations (steep hills adjacent to the salt marsh) will prevent any transgression in the upper reaches of the Kromme Estuary. Supratidal habitat in the upper reaches of the Swartkops estuary, if undeveloped, will provide the only viable habitat for the salt marsh to migrate into, given sufficient surface elevation.

The development of a late Holocene salt marsh was studied on the inactive part of the Fraser Delta at Boundary Bay, southwestern British Columbia. Present-day vegetation zones near 64th Street, South Delta, in the western part of the Bay, were distinguished in the salt marsh and were related to zones found in cores obtained in a transect across the marsh. A sequence of development, related to elevation, was determined. Salicornia and Triglochin are pioneer colonizers of the tidal flats and are sometimes associated with areas elevated by algal mats. As the area was elevated, sediments were trapped by vegetation and stabilized by rhizomes, and other halophytes grew, including Cuscuta, Sperqularia, Atriplex, Distichlis, Grindelia, and Plantago. A zone characterized by abundant Atriplex represents positions of former strandlines. As further emergence occurred, mesophytes became dominant and, in the landward, most emergent zone, a diverse flora of Maius, Sjdalcea, Aster, AchiIlea, Solidaqo, Elymus, Angelica, Juncus, and grasses developed. A radiocarbon date on Salicornia-rich organic silts at a depth of 35 to 40 cm in core 5 suggests that salt marsh development commenced 320 ± 70 years B.P. (GSC-3186). A former salt marsh peat is now partially buried and being actively eroded where exposed near 112th Street, South Delta, in eastern Boundary Bay. A paleoenvironmental reconstruction suggests the peat started developing in freshwater, with ferns, sedges, Typha, and Nuphar. Later, it was successively inundated by marine water and a salt marsh developed, as seen by an increase in the abundance of chenopod pollen. Subsequent emergence of the salt marsh was accompanied by the development of an increasingly diverse vegetation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Research in salt marshes dominated by the grass Sporobolus alterniflorus indicates that plant characteristics affect fiddler crab burrowing and in turn, crab activity can enhance primary productivity by increasing soil oxygen and nutrient cycling. Crab-plant interactions are less understood in microtidal Gulf Coast marshes compared to Atlantic Coast tidal marshes. It is unknown how structure of the dominant Gulf Coast vegetation zones (salt marsh, brackish marsh, fresh marsh and salt pannes) affects density of crab burrows and how burrows may influence primary productivity. I hypothesized that fiddler crabs would be most abundant in marsh zones with intermediate substrate hardness and vegetation density (Goldilocks Hypothesis). A seasonal habitat preference study was conducted during 2016-2017 in tidal marshes at Grand Bay National Estuarine Research Reserve in coastal Mississippi using burrow density as a proxy for crab abundance. Plant above- and below-ground biomass, burrow proximity to vegetation, and soil hardness were also surveyed as potential drivers of fiddler crab populations. The results indicated that fiddler crabs burrow in all four zones, but to varying degrees, and that burrow density was highest during autumn. The fresh marsh had the highest average density of burrows, as well as vegetation and soil parameters most representative of intermediate habitat, thereby supporting the “Goldilocks Hypothesis”. The brackish marsh also proved to be important fiddler crab habitat. Preferential fiddler crab usage of habitat upslope of salt marsh, e.g., fresh and brackish marsh, in Gulf Coast sites suggests that they may avoid immediate impacts of rising sea levels and possibly even migrate to higher ground if needed.

The purpose of this research was to examine the relationship of two approaches to visual assessment of landscape--the qualitative descriptive inventory and the theoretically-based empirical perceptual preference approach. Three levels of landscape visual units based on bio-physical similarities (landscape units, setting units, and waterscape units) were identified in a marsh (CUtler Reservoir, Cache County , Utah), and its tributary streams. Color slide photographs were taken from five of the visual units. These slides were rated on a 5- point scale by panels of judges for the expression of four perceptual variables--coherence, complexity, mystery, and legibility. The same slides were rated on a 5-point scale by 98 respondents according to their preference for each slide. The relationship of the visual units, perceptual variables, and preference was evaluated by analytical and statistical procedures. Results showed significant differences in the expression of the four perceptual variables between rivers and marshes and between setting units~ Both rivers and marshes were considered coherent when there were similarities in vegetation within the respective types; however, the strong horizontal organization of the marsh scenes necessary for coherence contrasted with the edge definition and orderliness considered necessary in rivers. Mystery was also related to similar factors in rivers and marshes (such as obscuring vegetation, particularly in the marsh) but the presence of riverbanks and bends in the river corridor had a distinct effect on mystery ratings in the river scenes . Complexity in both rivers and marshes was primarily dependent on diversity of vegetation and visual depth , but the number of different visual elements in river scenes also influenced complexity. Legibility was related to straight, enclosed and simple corridors in river images and to simple spaces with regular vegetation in marsh images. Fine textures and clear spatial definition enhanced legibility. Preference ratings were significantly different between rivers and marshes, but not between river setting units or waterscape units. River scenes received higher preference ratings than marsh scenes. Mystery , complexity, and visual depth were especially important to preference. Demographic variables of age, sex, academic major, and home state did not significantly affect preference. Statistical analysis indicated each perceptual variable was an independent predictor, and that compared to visual units, perceptual variables were more strongly related to preference.

Purpose and scope Each year thousands of western waterfowl succumb to disease, predators, mechanical injury and other decimating factors . Based on a review of records it is conservatively estimated that an average of 25,000 ducks have succumbed to botulism on western marsh areas annually. In a recent study, the United States Fish and Wildlife Service valued each duck and goose at $8.00 (McLeod, 1950). Applying this value to the estimated annual numerical loss, a total of $200,000 has been lost each season in mortality of western waterfowl from botulism. Control of this malady would reduce annual waterfowl and monetary losses. Prevention and cure are the only means of controlling botulism in wild ducks. At present, no economical preventative measure exists and control is based on curing stricken birds. The purpose of this study was to evaluate the cost of treatment and rate of recovery of birds stricken with botulism when treated by selected methods . The 4 treatments selected for evaluation were: (1) hospital inoculation, (2) fresh water, (3) field inoculation, and (4) no treatment or control . Research included a comprehensive evaluation of factors such as age, sex, species, body condition, degree of affliction, reaction to various amounts of antitoxin, and reaction t o selected treatment methods, thought to be pertinent in botulism control. This study was conducted during botulism outbreaks of 1953 and 1954, and was confined to state-owned marshlands of Utah. Study areas Three major areas provided sick birds used in this research: (1) Ogden Bay Refuge, (2) Farmington Bay Refuge, and (3) the Public Shooting Grounds . These man-made marsh areas are located on the saline flat lands adjacent to Great Salt Lake. The majority, 1,979 or 89.3 percent, of sick birds were taken from Ogden Bay Refuge on the Weber River Delta. This state-owned waterfowl refuge contains approximately 13,700 acres of diversified habitat . Excellent conditions for the production and existence of Clostridium botulinum, type c, the causative agent of botulism, were apparently present throughout the area. Farmington Bay Refuge, approximately 20 miles south of Ogden Bay Refuge in Davis County, Utah, was dried for improvements in 1953, but was traversed regularly during the 1954 season. In preparation for the hunting season, water was diverted into the north lake of Farmington Bay on October 1, 1953. A two-man crew picked up and disposed of approximately 2,000 dead ducks from approximately 20 acres of the reflooded marsh on October 6, 1953. This was the most serious outbreak of the study and indicated the rapidity with which sickness advanced. Few sick birds were noted, which indicated that the crisis had passed. Farmington Bay Refuge provided 121 of the 2,214 ducks treated during 1953 and 1954. Not more than 12 sick or dead birds were seen on the Public Shooting Grounds, 8 miles west of Corinne, Utah, in 1953. During the 1953 season, 3 sick birds were transported from the area to Ogden Bay Refuge for treatment. In 1954 this state-owned shooting area supplied lll sick birds for treatment. Other areas were observed during the study but did not provide sick birds for treatment. These areas consisted of : (1) State -owned lands beyond Bear River Migratory Bird Refuge, and (2) Smith and Utah Lakes west of Provo, Utah.

Any marsh is a distinctive land-forrm of varied interest. To the agriculturist it is wasteland to be reclaimed; to the naturalist, a habitat of aesthetic value. To the ecologist, however, a marsh represents a complexity of vegetation under the influences of many and often inseparable factors. It becomes a place of challenging study. There exists a notable lack of information treating the ecology of inland salt-marshes. Still less known are the ecological conditions imposed upon plant life in marshes arising from saline springs. The presence of such a wetland in western Utah afforded the opportunity to study salt-marsh vegetation in a highly specialized habitat. The study had two phases. First was a study of the vegetation. Data were secured from collections and study plots within each of the major marsh communities. General descriptions of other plant life were additionally compiled. It is not within the scope of this paper to discuss or rigidly define the requirements embraced in the use of "community" as a unit of vegetation. Sufficient references are available for those who wish to pursue the point. In this study, a community is a congregation of plants exhibiting differences in appearance and species composition from other plant congregations. Secondly, studies were directed to the influences of soil and water on the ecology of each community. Transects were used to investigate many of these relationships. Transition zones between communities were narrow and usually sharply delineated. Transects intersected ecotones of this sort; environmental differences which may have occurred in the few broader ecotones were assumed to be of equal magnitude but of more gradual rate of change . Relatively short transects thus adequately represented each community yet allowed collection of intensive data. Information and data were collected during a 5-week period in August and September 1959 and a 6-month period beginning in March 1960.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 161-166. / by Jayne Loring Fifield. / M.S.

No description available.

In order to improve our understanding of present and future coastal environmental change, we look into the past using sediment that accumulates in coastal environments. We have done this for two disparate systems: a back-barrier lagoon in southwestern Japan, and freshwater tidal marshes along the Hudson River, New York, USA. In Japan, we used a 2,500-year sediment record to investigate coastal flood risk from tsunamis and typhoons. This is a critical area of study to better understand the spatial and temporal variability of these hazards in Japan. In the Hudson River we looked at modern (since 1800) deposition of sediment in anthropogenically constructed embayments that have formed tidal wetlands in the last few centuries. A better understanding of the factors that have attributed to these successful tidal marsh systems in the past can help inform future management decisions in the face of future sea level rise. Studying the history of coastal systems using the sediment record is a valuable tool for assessing hazard risk and habitat loss in the present and future.

In 1985, 24 bottom samples were collected in each of two slightly brackish,semi-permanent prairie wetlands (P1 and P4) with different hydroperiods. The main objective was to determine if hydroperiod affected seed pool characteristics. Additionally, 48 samples were collected in 1986 from wetland P1 to determine if seed bank composition changed annually without a change in mature vegetation. Seed bank composition was determined by placing soil samples in a greenhouse, then counting and identifying emerged seedlings. As a check against the seedling emergence method, seeds were separated and identified microscopically in one-third of the 1985 samples. Results indicated that the emergence method was an accurate technique for assessing seed pool composition. The wetlands did not differ in floristic composition (i.e., presence/absence) but did in species densities. The mean relative density of mudflat annuals in all seed pool samples was significantly greater in wetland P4 (82%) than in P1 (52%). A shorter hydroperiod in this wetland produces more frequent drawdowns and a greater input of mudflat annual seeds. Conversely, seeds of emergent species were more abundant in the seed bank of wetland Pl (48%) compared to P4 (17%). The former wetland has a longer hydroperiod and less frequent drawdowns, and thus, the primary seed input is from emergent plants. / Master of Science