Department or Program

Geology

Abstract

The Southern Alcove (S. Alcove) of Sprague Marsh in Phippsburg Maine is a section of back barrier salt marsh that has been tidally restricted by the installation of a ditch plug into its main stream channel since the early 2000s. Previous research in the area has shown that the mean water level upstream of the ditch plug within the S. Alcove is significantly higher than the downstream area (Barry 2012). The purpose of this study is to provide more research and information on the condition of the S. Alcove (nearly ten years after it was last studied), as well as provide insight as to whether or not the ditch plug should be removed. This was done by monitoring fluctuations in the groundwater levels, assessing sedimentation rates, and analyzing sediment cores for carbon content from within and from outside of the S. alcove. Up gradient of the ditch plug and in the S. Alcove, ground water response to tidal fluctuations was muted and sedimentation rates were higher than down gradient of the ditch plug. It was also found that approximately the first 5 cm of each sediment core was very rich in organic carbon, which has been seen in other ditch plugged environments along the east coast (Vincent et al., 2013). Studies show that persistently elevated water levels in salt marshes result in decreased marsh elevation, increased soil salinity, decreased soil redox potential, decreased soil strength, and decreased carbon storage capacity (Vincent et al., 2013). Thus, I recommend removal of the ditch plug in the S. Alcove on the Sprague River Marsh. , Careful attention must be paid to the methods of removal to ensure that the marsh is restored, and monitoring practices must be employed for several years after ditch plug removal to ensure that we learn more about how this system evolves with time.

Level of Access

Restricted: Embargoed [Open Access After Expiration]

First Advisor

Beverly Johnson

Date of Graduation

5-2022

Degree Name

Bachelor of Arts

Number of Pages

53

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