Department or Program

Earth and Climate Sciences

Abstract

Healthy salt marshes are among the most productive ecosystems on the planet. However, tidal restrictions can degrade a salt marsh, resulting in subsidence, decreased carbon dioxide (CO2) sequestration, and carbon outwelling, compromising the system’s efficacy as a carbon sink. This study examines carbon stocks and sequestration, greenhouse gas emissions, pore water salinity and sulfates, sedimentation, and refractory peat fraction at depth upstream and downstream of a tidal restriction in the Jones Creek Marsh, Scarborough, Maine, USA. The average carbon density in the upper 100 cm was 0.025 ± 0.015 g/cm3 and 0.035 ± 0.008 g/cm3 upstream and downstream of the restriction, respectively, indicating significantly lower carbon stocks in the upstream area (p = 0.0001). Preliminary estimates of carbon sequestration differed between 50 gC/m2yr upstream of the tidal restriction and 70 gC/m2yr downstream of the tidal restriction. Greenhouse gas fluxes analyses from June and July suggested that methane emissions were significantly greater upstream of the tidal restriction in June (p < 0.05), but not July. Methane flux was seemingly independent of both porewater salinity and sulfate concentrations. Above 20 cm, % refractory mass of the peat was highly dynamic. Below 20 cm, there was a significantly higher average % refractory mass upstream of the tidal restriction (M = 68.3 ± 5.8 %) than downstream of the tidal restriction (M = 55.0 ± 3.9 %) (p = 0.001), which raised questions about the efficacy of our estimations of long term carbon storage. Our data show that changes in marsh hydrology induced by the Snow’s Canning Road tidal restriction have effectively restricted tidal inundation to the west half of the Jones Creek Salt Marsh, and suggest that this restriction has a negative impact on carbon storage and sequestration upstream.

Level of Access

Restricted: Embargoed [Open Access After Expiration]

First Advisor

Johnson, Beverly

Date of Graduation

5-2024

Degree Name

Bachelor of Science

Number of Pages

87

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Embargoed

Available to all on Tuesday, April 01, 2025

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