As sea level rise (SLR) affects coastal wetlands, ecosystem responses can include vertical accretion, landward transgression, or submergence. Sea level rise-induced transitions can alter key biogeochemical transformations within wetland soils, impacting the ability of these systems to provide ecosystem services, specifically carbon (C) storage and water quality regulation. Through a series of complementary laboratory and field-based studies, biogeochemical responses to salinity, vegetation shifts, and submergence were investigated. Changes in nutrient dynamics associated with saltwater intrusion were evaluated by artificially adding saline water to different freshwater wetland soil types, indicating that potential exports of critical nutrients (forms of nitrogen, phosphorus, and C) out of freshwater wetland soils is mediated by soil type. A controlled laboratory experiment was conducted to determine the potential degradability of C stored within submerging coastal wetland soils under both aerobic and anaerobic conditions. Under aerobic conditions, 66% more carbon dioxide was produced than under anaerobic conditions and 4x greater carbon dioxide was produced at 90-100cm depths than at the surface. At the same site, the degradability of carbon stores was examined through organic matter fractionation, stable isotopic examination, and determining the abundance of key microbial genes. Both total soil C and stores of bioavailable nutrients increased with depth, while organic matter quality decreased. Finally, the biogeochemical impacts of two separate vegetation transitions occurring co-incidentally with sea level rise were investigated: mangrove encroachment into salt marsh, and more salt- and inundation-tolerant herbaceous encroachment into herbaceous marsh. Conclusions from these studies demonstrate that vegetation transitions alter both soil nutrient storage and fast-cycling nutrient pools, indicating that biogeochemical transitions occur in advance of changes in vegetative species dominance. Results from these chapters holistically address how biogeochemical functioning, specifically nutrient cycling, regulation of water quality, and C sequestration, within coastal wetlands responds to stressors associated with SLR.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Steinmuller, Havalend, "Biogeochemical Effects of Sea Level Rise-induced Transitions Within Coastal Wetlands" (2019). Electronic Theses and Dissertations. 6382.