Date of Award

8-1-2025

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Keith Walters

Second Advisor

Angelos Hannides

Third Advisor

Ryan Rezek

Additional Advisors

Erik Yando

Abstract

The coastal transition zone (CTZ) is a regional gradient linking terrestrial and marine systems, comprising of the terrestrial upland, the marsh-upland ecotone, and estuarine salt marshes. Along all US coastlines, including the South Carolina (SC) coast from Little River to Georgetown, increases in anthropogenic development of terrestrial uplands have altered the historically established vegetation, and various physical, chemical, biological, and geological gradients. Despite the CTZ's ecological importance, the trickle-down effects of terrestrial upland development on associated high marsh habitats remain understudied. Data were collected from developed (DEV) and undeveloped (UND) shorelines across three SC estuarine inlets. Multilevel modeling (MLM) was used to analyze treatment-specific differences and relationships between parameters (temperature, sediment characteristics, vegetation, gastropods, and nekton) across two contrasting seasons (summer and winter).

Contrary to initial thoughts, significant soil temperature differences at the upland did not cascade down the CTZ gradient to the marsh, and only maximum air temperatures were significantly different at the upland. Similarly, differences in select physical and biological gradients were significant at the upland and were not significant in other CTZ regions. Differences are likely attributed to increased freshwater and nutrient runoff at DEV shorelines due to upland vegetation absence and increased impervious surfaces. Additional differences in lawn maintenance frequency between seasons are potential contributors of some observed seasonal differences. Nekton dynamics between treatments could be attributed to seasonal predator-prey dynamics, with increased availability of predators, prey, and biological activity in summer. The power of the results obtained from the MLMs are likely to be increased with larger sample sizes for nested groupings, or alternatively, a stronger model to account for the study’s complexities to detect differences along the CTZ gradient between treatments. Significant differences were limited to a few parameters at the upland region of the CTZ.

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