Department or Program

Geology

Abstract

This project uses geochemical analyses of sediment cores to estimate the carbon density of tidally restricted and restored salt marshes in Phippsburg, Maine. Analyses were focused on three different hydrological regimes: the Small Point Marsh which has been tidally restricted for decades; the northern part of the Sprague Marsh which has had tidal flow restored for 17 years; and the southern part of he Sprague Marsh which has had full tidal flow since it was formed. The purpose of this study is to determine how tidal flow restrictions from undersized culverts can affect the carbon density and therefore the health of a tidal salt marsh system. A total of 13 1- meter long sediment cores were collected in the field using a gauge auger. They were subsampled and analyzed for dry bulk density and loss on ignition (LOI), and carbon densities were calculated. These values were compared to the national average carbon density of tidal salt marshes, 0.055 g/cm3 as determined by Hinson et al., 2017. The Small Point marsh had the highest carbon density of the three sites, at 0.0507 g/cm3. North of the causeway at Sprague had an average measured carbon density of 0.0309 g/cm3 and south of the causeway at Sprague had a measured average carbon density of 0.0439 g/cm3. Assuming the carbon density values south of the causeway at Sprague are baseline values representing a fully functional marsh, the lower carbon density north of the causeway implies that the system had only been partially recovered after 17 years of tidal restoration. The high carbon density values at Small Point marsh likely results from one or a combination of the following factors: the vegetation type, biogeochemical cycling in the soils so that carbon is preserved, and/or the hydrological restriction is not effectively restricting access to marine inundation. This study is important in proving that differences in carbon density result from multiple factors in salt marshes. Salt marshes are becoming vulnerable to sea level rise as climate change occurs.

Level of Access

Restricted: Embargoed [Bates Community After Expiration]

First Advisor

Beverly Johnson

Date of Graduation

6-2021

Degree Name

Bachelor of Arts

Number of Pages

38

Embargoed

Available to Bates Community via local IP address or Bates login on Tuesday, April 12, 2022.

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