Date of Award

Spring 2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Committee Chairperson

Megan Fork, PhD

Committee Member

Jennifer Chandler, PhD

Committee Member

Jessica Schedlbauer, PhD

Abstract

Freshwater salinization, especially the use of road salts for deicing, poses significant threats to freshwater wetlands. The Great Marsh in Elverson, Pennsylvania, is a unique and valuable freshwater ecosystem, and the largest contiguous freshwater wetland complex within the highly developed Philadelphia suburban landscape. Recently documented water quality and vegetative community degradation within the Marsh could be attributed to the Pennsylvania Turnpike, present along the Marsh’s southern boundary. Constructed in the 1950s, the Turnpike is a source of road salts and pathway for invasive species, namely the salt-tolerant Phragmites australis. To investigate the effects of road salt intrusion on emergent wetland vegetation communities, I quantified sodium and chloride concentrations in shallow soils and groundwater and collected vegetation abundance data along transects extending into the Marsh from the Turnpike. Although elevated road deicing ion concentrations were detectable throughout the year, concentrations did not decrease with increased distance from the Turnpike. However, concentrations were highly variable adjoining the Turnpike - indicating that stormwater infrastructure likely influences road salt intrusion. Vegetation diversity decreased, and invasive species presence increased, with increased deicing ion concentrations in soils, but not groundwater. When controlling for a suite of environmental variables, P. australis presence and soil sodium concentrations were the primary drivers of plant species diversity. Finally, soil sodium concentrations in wetland soils could be influenced by flowing water in the wetland, based on stream models. Understanding the impacts of road salts on freshwater wetlands will continue to increase in importance as anthropogenic disturbances continue to threaten freshwater wetlands.

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