Date of Award

Winter 2019

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

Ruth K Varner

Second Advisor

Julia G Bryce

Third Advisor

Wilfred M Wollheim

Abstract

Freshwater ecosystems, such as streams and fluvial wetlands, are a subset of global aquatic ecosystems and produce and emit significant amounts of the greenhouse gases (GHG) methane (CH4) and carbon dioxide (CO2) to the atmosphere. In temperate regions, freshwater ecosystems often contain fluvial wetlands, which form the boundary between stream and wetland ecosystems. In fluvial wetlands, oxygen- and nutrient- poor soils are continuously fed by upstream river networks, which have the potential to create ecosystems with enhanced GHG production and emissions. The magnitude and seasonal variability of natural GHG emissions from freshwater fluvial wetlands, though highly understudied, have been suggested to significantly contribute to global GHG budgets, a critical concern as the pace of climate warming accelerates. This study reports assessments of a full year of seasonal patterns and potential drivers of GHG emissions from a temperate fluvial wetland dominated river continuum. Methane and CO2 emissions were measured using a static chamber method at six locations along the Ipswich and Parker River Watersheds, northeastern Massachusetts, U.S.A. The results indicate that emissions correlate with dissolved organic carbon (DOC) and water temperature for both gases, where CH4 was additionally influenced by dissolved oxygen content (DO) and CO2 by total dissolved nitrogen and sulfate. Additionally, summer emissions only account for 48% of annual emissions, and indicate accordingly that winter and shoulder seasons must be included for fully accurate predictions of global freshwater GHG emissions and associated drivers.

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