Department or Program

Geology

Abstract

This thesis compares carbon stocks, sequestration rates, and changes in vegetation history in the eastern lobe of Cousins Marsh, Yarmouth, Maine and in Old Pond Marsh, Hancock, Maine. Both of these marshes have been modified by human activity. Interstate 295 was built over Cousins Marsh in the late 1950s, while Old Pond Marsh has an 1880s railway cutting across the southern cove and a man-made channel adding another tidal influence to the North end. Seven peat cores were taken throughout each marsh, totaling 14. All cores were subsampled and analyzed for total organic content (% LOI), two cores from each marsh were analyzed for carbon and nitrogen isotopes, and one core from each marsh were analyzed for lead concentration. Changes in δ13C suggest significant changes in vegetation over time, which may indicate changes in relative sea level, land use, or hydrology. Patterns in δ13C, density, and carbon indicate that stream channel meanders alter the carbon storage: locations on the inside of a stream bend generally have higher density and lower carbon content than locations on the outside of a bend. Lead concentrations were used to establish a pollution horizon and calculate accretion rates of 2.4mm/yr in Cousins and 2.0mm/yr in Old Pond. A relationship between total organic content and carbon content was established by linear regression (% C = 0.4513 (% LOI) + 0.2419; R2 = 0.9557), which is similar to published literature. Carbon density is generally highest in the centers of each marsh, with lower values on the edges and in more upland areas. Despite differences in location and human alteration, rates of carbon sequestration were very similar, at 77.8 ± 10.2 g C m-2 yr-1 for Cousins and 72.0 ± 16.2 g C m-2 yr-1 for Old Pond. From average carbon density and marsh area, the carbon stock of the top 60 cm was determined to be 16.5 million kg of carbon for Cousins and 6.3 million kg of carbon for Old Pond. Accurate carbon stocks are essential for carbon budgets and prioritizing conservation work.

Level of Access

Restricted: Embargoed [Open Access After Expiration]

First Advisor

Johnson, Beverly

Date of Graduation

5-2022

Degree Name

Bachelor of Science

Number of Pages

124

Components of Thesis

1 pdf file

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