Theses and Dissertations

Date of Award

7-1-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean, Coastal, and Earth Sciences

First Advisor

Alejandro Fierro Cabo

Second Advisor

Carlos E. Cintra Buenrostro

Third Advisor

Engil Isadora Pujol Pereira

Abstract

Coastal wetlands are important ecosystems that provide numerous ecosystem services including erosion control, habitat for fauna, and carbon sequestration. Notably, coastal wetlands are producers of greenhouse gases (GHGs) but are able to store significant amounts of carbon relative to their surface area. Mangrove forests are amongst the most effective ecosystems for carbon sequestration. Soil emits (GHGs) containing carbon (such as carbon dioxide (CO2) and methane (CH4)), which are produced by organic matter decomposition and soil organic carbon mineralization, and both are an important component of the global carbon cycle. Soil emissions may be affected by a variety of factors including soil salinity, inundation, soil texture, soil layers, vegetation cover, leaf litter decomposition, and biotic activity from fiddler crabs. The purpose of this study was to isolate these specific factors and quantify GHG emissions in the mangrove and linked vegetation of the southernmost portion of the Lower Laguna Madre, a hypersaline lagoon of south Texas. It was hypothesized that salinity increases gas production, inundation decreases gas production, finer-grained soils and deeper layers have reduced gas production, leaf litter decomposes fastest in low vegetation intertidal zones, and biotic activity increases fluxes. Results indicate that inundation decreased CO2 production by 17% while CH4 was not affected. Extreme hypersalinity reduced CO2 production by 27-31% while CH4 production was higher overall at a polyhaline level. Texture did not have an effect on CO2 production, while finer-grained soil resulted in higher CH4 production. Respired C was 4% and 41% higher from sandy loam soil compared to clay soil for surface and subsurface layers, respectively. Surface soil layers resulted in higher production for both gases. Leaf litter decomposition was 10-12% faster in the more elevated intertidal zone dominated by Batis maritima compared to the algal mudflats and Avicennia germinans zones. Lastly, CO2 fluxes were ~200 times higher in areas with a lower crab burrow density. This study provides important insights of ecological factors affecting soil emissions of two GHGs in an understudied hypersaline estuary. This study contributes to the understanding of an ecosystem susceptible to the negative effects of sea level rise, climate change, and an increasing anthropogenic footprint.

Comments

Copyright 2024 David R. de la Garza. https://proquest.com/docview/3116106070

Download

Share

COinS