Department or Program
Earth and Climate Sciences
Abstract
Salt marshes are regarded as key blue carbon stocks with high rates of carbon sequestration due to tidal inundation. However, the impacts that rising sea levels and human development and alterations to salt marshes have on carbon stocks and organic matter deposition have yet to be fully understood. The Sprague River Marsh, in Phippsburg Maine, has been subject to many alterations through the last 400 years (ditching, the building of a tidal restriction and the dredging and redirection of the natural tidal channel). This study analyzes the geochemical records (% carbon, C/N ratio, δ13C, d15N, and carbon density) of 40 previously collected sediment cores and 3 new sediment cores, from the Sprague River Marsh. The geochemical data were parsed into six different time intervals (0-50, 50-100, 100-200, 200-300, 300-500, 500-1000, 1000-2000 yrs BP) based on an age model derived from 13 radiocarbon dates. Geochemical data was analyzed for correlation with remote sensing data and the resulting correlated environmental covariates were used to model and map marsh surfaces using EBK Regression Prediction in ArcGIS Pro. These marsh surface reconstructions date the shift from tidal flats to salt marsh around ~1000 yrs BP, the location of the historic tidal channel, and an increase in spatial variability of % C and δ13C post European Colonization. Additionally, the reconstruction of carbon density revealed a lack of correlation to any of the environmental covariates explored in this study. Consequently, carbon density appears to be difficult to model using remote sensing. Human alterations to marsh hydrology may have contributed to the increase in % C and δ13C spatial variability and unpredictability of carbon density. This suggests further research is needed to fully understand the connection and scope between marsh alterations and carbon density in order to more easily predict carbon stock.
Level of Access
Restricted: Embargoed [Open Access After Expiration]
First Advisor
Johnson, Beverly
Date of Graduation
5-2025
Degree Name
Bachelor of Science
Recommended Citation
Welch, Adelle R., "High Resolution Mapping of Carbon Stocks and Sequestration and Organic Matter Sources over the last 4000 Years in the Sprague River Marsh, Phippsburg Maine" (2025). Honors Theses. 501.
https://scarab.bates.edu/honorstheses/501
Number of Pages
75
Components of Thesis
1 pdf file
