RECONSTRUCTION OF THE POST-GLACIAL HISTORY OF THE PEDDOCKS ISLAND SALT MARSH, HULL, MA

The study of environmental change is becoming an issue of utmost importance in today’s age. Climate change and associated sea-level rise are of a large concern, and studying the environment’s history will allow for better predictions on the future. Salt marshes provide an excellent site for the study of changes that have occurred. Salt marshes accrete at a rate synonymous to sea level rise, providing an excellent source of data. Marsh peat also sequester large amounts of carbon, acting as a “carbon sink.” This project involves the reconstruction of the history of a marsh found on Peddocks Island in Boston Harbor, Hull, MA. The analysis of several sediment cores taken throughout the marsh provides the basis for the reconstruction of the marsh history. Vegetation pattern and surficial geological mapping are also included in the framework of this study.

The Peddocks Island salt marsh is an extremely dynamic area, as the growth of the marsh coincides with an incoming gravel outwash fan from the Southern end. Diurnal tides flood the marsh and pour into two small lagoons on the North and South ends of the marsh. Sediment cores ranging from 0.4 m to 1.6m were taken using both a 1 in. and 3 in. diameter Dutch Corers. Cores were taken in the low marsh, high marsh, and higher high marsh zones, identified by their respective mean high tide levels and vegetation patterns. All cores contain an uppermost “active root zone” layer of light brown peat, followed by a darker peat containing various roots and rhizomes. Several cores also extend to a greenish-gray clay at about 1 meter deep. LOI (Loss on Ignition) data shows a decrease in organic carbon down through the marsh peat to the clay. Peat layers contain an average 18.128 % LOI, and clay layers a 2.991 % LOI. Grain size analyses throughout the lengths of the cores show evidence of storms events and sea level rise. Radiocarbon dates of the marsh peat will allow the data to be put into a geochronological context. With these results, interpretations on sea level rise in Boston Harbor and the future of the Peddocks marsh can be extrapolated.