Degree

Doctor of Oceanography and Coastal Sciences (POCS)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

Mangroves are blue-carbon-rich wetlands that can potentially contribute to climate change mitigation policies. However, mangroves are increasingly impacted by both natural and human disturbances worldwide that require restoration and rehabilitation programs to advance their conservation. Yet, there are major knowledge gaps in our understanding of how local resources (nutrients), regulators (e.g., salinity) and hydroperiod gradients interact in controlling mangrove role as carbon sink or source at different spatiotemporal scales under increasing disturbance frequency and climate change.

Here, I developed a mass-balance-based hydrology model to estimate soil porewater salinity (PWS) in riverine mangroves along the Shark River estuary (SRE), South Florida; model results matched the PWS decreasing trend from downstream to upstream. Multiple simulation scenarios showed that freshwater inflow associated with upland restoration and sea level rise are key drivers controlling mangrove PWS in this karstic coastal region.

I also evaluated the role of tropical cyclones (TCs) in controlling particulate organic carbon flux (POC; Net Primary Productivity Litterfall, NPPL) between mangroves and estuarine waters in the SRE. This POC flux varied within a wide range of TCs integrated kinetic energy (IKE). POC fluxes (71–205 g C m−2 year−1) are similar to observed dissolved inorganic carbon (61–229 g C m−2 year−1) export and previously unknown. A statistical model between an IKE-based pulsing index and NPPL is proposed to determine TCs impact on mangrove role as carbon sink or source. I recommend including cyclone-induced POC exports to reduce uncertainty when constructing carbon budgets at regional scales.

Given the controlling role of regional temperature (macroclimate) and hydroperiod in soil biogeochemical processes, I investigated temperature differences or offsets among free air, vegetation canopy (microclimate), overlying water and soil in mangroves and marshes in subtropical (Louisiana) and tropical (Florida) latitudes. Results showed the critical role of water flooding duration and frequency in buffering daily and seasonal change in air temperature thus reducing plant stress; especially, during extreme weathers (cold fronts and TCs) that cause canopy defoliation.

Together, these studies contribute to the development of mangrove spatially-explicit demographic and Earth System models to implement both mangrove restoration projects and climate change mitigation policies.

Committee Chair

Rivera-Monroy, Victor H.

Available for download on Wednesday, October 16, 2024

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