Coastal marshes and wetlands are vital natural resources that offer habitats for plants and animals, serve as ecological filtration for soil and water pollutants, and act as protection for coastlines. Fishing, both commercial and sport, has a large economic impact in the study area – the Gulf Coast between Galveston Bay, TX and Oak Grove, LA. The objective of this research was to determine the contribution of Hurricane Ike storm surge sedimentation to long-term marsh aggradation in Texas and Louisiana coastal marshes. The research hypothesized that Hurricane Ike’s storm surge deposit would be equal to decades and possibly even a century’s worth of the average annual non-storm sedimentation. A quantitative field study was performed. The storm surge deposit was examined in a series of 15 transects covering approximately 180 km east of Hurricane Ike’s landfall. Nine of the 15 transects were re-surveyed a year after the initial measurement to assess preservation of the deposit. The results demonstrate that Hurricane Ike contributed between 10 to 135 years’ worth of sediment to coastal marshes along the coasts of Texas and Louisiana, and the sediment deposits have been preserved for over two years.

The structure and function of coastal marshes results from a complex interaction of biotic and abiotic processes that continually influence the characteristics of marsh vegetation. A great deal of research has focused on how tidal processes influence vegetation dynamics along the Atlantic coast, but few studies have investigated the influence of similar processes in the marshes along the Gulf of Mexico. This study aims to identify the characteristic vegetation assemblages of the coastal marshes bordering the East Bay of Galveston Bay, Texas, and identify if elevation, inundation frequency and burning frequency are important to their structure. To identify characteristic vegetation assemblages, hierarchical cluster analysis was used. The cluster analysis resulted in seven statistically different vegetation assemblages that were used in diversity analysis and classification and regression analysis (CART) as dependent variables. Diversity measures were calculated at both the plot and assemblage scale using Shannon's diversity index and species richness. The resulting diversity measures were used as predictor variables in the CART analysis as well as regression analysis. Hydrologic modeling was accomplished using Mike 21, a flow and wave simulation model, along with a geographic information system (GIS), to model hourly inundation frequency at each of the sampled plots. The inundation frequency was then used as a predictor variable in the CART analysis and regression analysis. This study found that the main factor contributing to species richness was elevation. Vegetation assemblages at high elevations generally had high diversity, and assemblages at low elevations had lower diversity. Elevation and inundation frequency are inversely related, and the strong correlation between species richness and elevation also assumes that inundation frequency is important in structuring the marsh. Burn frequencies had no influence on diversity in general, but more frequent burning did result in monospecific stands of Spartina patens at Anahuac NWR.

<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)

Concern over recent declines in many wetland-dependent bird species has led to a need to monitor marsh bird populations in response to anthropogenic activities. I conducted point counts and vegetation surveys at 26 coastal wetlands in the Laurentian Great Lakes Region of Canada from 2006-2008 to determine 1) effective methods to monitor marsh birds, and 2) the impacts of land use surrounding coastal wetlands on marsh bird communities. The first part of this dissertation showed that call-broadcasts are effective tools for monitoring marsh birds and that point counts for marsh birds should be conducted from both the shoreline and from the interior of large marshes. Because of the species-area relationship for wetland birds in southern Ontario, sampling effort should increase proportionally with wetland area to attempt the detection of all species present. In the second part of this thesis, I showed that marsh obligate-nesters preferred wetlands in rural areas as opposed to urban areas, while generalist marsh-nesting species showed no apparent difference in use. The Index of Marsh Bird Community Integrity (IMBCI), a biological index used to indicate wetland health, was significantly higher in rural than in urban marshes. Marsh isolation was also an important factor in predicting the marsh bird community, with more isolated wetlands containing fewer obligate species and associated with a lower IMBCI value. Wetlands of Georgian Bay were found to have quite different bird and plant communities than wetlands of Lake Ontario. Even though wetlands of Lake Ontario were considerably more degraded than those in Georgian Bay (according to land use alteration and degree of water quality impairment), these two regions produced similar IMBCI scores, and this draws into question the applicability of some indicators on a basin-wide scale. The results of this thesis indicate how survey protocols in existing wetland bird monitoring programs should be modified and support current literature that urbanization negatively affects the marsh bird community. </p> / Thesis / Doctor of Philosophy (PhD)

Nature-based solutions (NBS) are promising strategies for protecting vulnerable coasts in the context of climate change, utilizing the coastal protection capabilities of natural ecosystems for engineering applications. The ability of coastal marsh vegetation to attenuate wave energy and prevent coastal erosion has been acknowledged for decades, however, consideration for their use in coastal protection strategies is presently limited, particularly in Canada due to a lack of engineering guidelines and limited available research considering region-specific variables. Physical modelling presents a useful tool for investigating the coastal protection function provided by marsh vegetation in a controlled, repeatable environment, which can ultimately inform the design of nature-based coastal protection strategies. To date, such studies have investigated the influence of plant biophysical parameters (stem flexibility, width, and height) and hydrodynamic conditions (wave height, wave period, and plant submergence) on wave attenuation. These studies have used either live vegetation, requiring full-scale wave testing, or surrogate vegetation, which allows simplified testing at either full- or reduced-scale. Overall, live vegetation studies have been limited in the variety of saltmarsh plants considered, with few studies considering plant species native to the Canadian coastline. Several physical modelling studies have been performed using surrogate plants, however, methods of surrogate development for flexible vegetation or reduced-scale testing are not yet well developed. This thesis aims to address knowledge gaps pertaining to the use of marsh vegetation in coastal protection strategies, particularly through the development of experimental methods with both live and surrogate plants. A full-scale flume study with live vegetation was performed to develop fundamental knowledge of wave-vegetation interactions for Spartina alterniflora and Spartina patens, two salt marsh species native to Canada’s Atlantic coast. S. alterniflora was observed to demonstrate a resistance strategy in response to hydrodynamic forcing, versus the avoidance strategy of S. patens, supporting complementary functioning of the two species if utilized together in coastal protection schemes. Observations of plant properties and stem bending from live plant tests were subsequently applied in the development of a small-scale flume study, which examined wave attenuation associated with a downscaled S. alterniflora meadow in the configuration of a “living dyke” structure. Wave damping induced by surrogate vegetation was observed to be minimal for the tested wave conditions (0.073 m < Hm0 < 0.225 m, 2.0 < Tp < 3.2 s, 1:4 scale) and beach slope (1V:20H), with wave height evolution dominated by wave shoaling and breaking. Several methods were considered for modelling the S. alterniflora meadow at reduced scale, and results demonstrated a sensitivity to surrogate diameter but not flexibility. The development of robust experimental methods for investigating the performance of nature-based coastal infrastructure is essential for the establishment of appropriate design conditions. The scale series approach of this thesis supports such methodological advancements and is expected to make preliminary contributions to design guidance on coastal marsh-based NBS and provide critical direction for future studies.