Date of Award

5-31-2022

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Jarrett Byrnes

Second Advisor

Ron Etter

Third Advisor

Mayra Vidal

Abstract

Globally, 25-50% of salt marsh area has been lost due to anthropogenic impacts, including sea level rise (SLR). Sea level rise impacts can be slowed by vertical accretion of sediments and organic matter. While sedimentation at large-scales is determined by supply, sediment availability, flow rates, and marsh topography, at small scales modification of flows by vegetation might alter sedimentation rates. Sedimentation rates in marshes are likely influenced by Spartina that slow water flow. Sites representative of a SLR-future have stands of S. alterniflora that differ in height, stem diameter, stem density, and blade width; relative to marshes more representative of current conditions in New England. Little has been done to directly test how sedimentation is influenced by these different morphologies. We aim to bridge that gap by measuring sedimentation in two experiments simulating the forms of S. alterniflora at the creek bank edge. We first manipulated natural plant heights to evaluate height sensu stricto on sedimentation. We then used artificial S. alterniflora patches varying in height, stem diameter, stem density, and blade width to test morphological differences in current versus future stands. In both experiments, treatment differences were found in only a subset of locations, indicating that any small-scale effects of plant morphology on sedimentation are modified by abiotic factors, such as elevation of the marsh. A marsh’s ability to accrete vertically and outpace sea level rise is therefore dependent on both the physical characteristics of a marsh and plant morphology in combination. Understanding interactions between physical habitats and marsh vegetation will help us to understand when and where sea level rise might have some of its most profound effects on salt marshes.

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