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theses

Tidal marshes are important habitats for wildlife, and they provide a wide variety of ecosystem services, one of the most important of which is carbon storage and sequestration. Studying and modeling carbon storage in tidal marshes is very difficult due to the highly variable, highly site-specific biogeochemical processes that occur within them. Many studies attempt to understand the environmental factors that impact carbon storage in tidal marshes, but few assess marsh sediments at depths below 1 meter; therefore, this study seeks to understand the influence of environmental factors (spatial location, elevation, vegetation/sediment type) on carbon storage and to estimate total carbon stored throughout the entire depth of the marsh sediments. 16 cores were collected to refusal in a small urban tidal marsh, and percent organic carbon and organic carbon density were assessed along the full core depth. Interpolation maps of sediment thickness and carbon storage were generated to estimate total carbon stocks. Average carbon stocks were similar to those collected by previous studies, but total carbon stock estimates were over three times higher than the assessment that included the sediments above 1 meter; while studies that only assess the top meter may be useful, assessing the true depth of marsh sediments could be key to gauging the potential of tidal marshes in sequestering and storing carbon. Trajectories of percent organic matter throughout each core depth suggested that the landward portion of the study site may have vegetated first, likely as a freshwater wetland, while the seaward portion may have formed later under the influence of sea level rise and tidal regimes; as sea level gradually increased over time, the entire study site transitioned into a tidal marsh system. Surface elevation and distance from creek showed no relationship to organic matter or carbon density, while both percent organic matter and organic carbon density showed significant variation when grouped by sediment type. Percent organic matter was significantly higher in areas covered by Spartina patens than areas covered by Phragmites australis. Further research is needed to clarify the relationship between tidal marsh carbon storage and environmental factors such as sea level, tidal regimes, vegetation, elevation, spatial distribution, salinity, and other factors that may add to the complexity of biogeochemical interactions. If we can better understand the true depth of tidal marsh sediments, as well as how environmental factors may have impacted organic matter storage in the historic past, then we may be better able to predict how changing environmental conditions may alter carbon storage potential in the future. Now more than ever, it is essential to study the dynamics of these important blue carbon systems so that we can better approach tidal marsh management in the face of global climate change.

ETD_11251

M.S.

Includes bibliographical references

ETD graduate

doi:10.7282/t3-0p1v-3429

The author owns the copyright to this work.