Theses and Dissertations

Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Abdullah Rahman

Second Advisor

Dr. Heather Alexander

Third Advisor

Dr. Carlos E. Cintra Buenrostro


As atmospheric CO2 concentrations continue to rise, understanding factors that influence size and longevity of carbon (C) pools within coastal and marine ecosystems (i.e., “blue carbon”) is critical. In 2013, the global average atmospheric CO2 concentration reached 396 ppm, which was the highest recorded level in the last 800,000 years. Recent research acknowledges the importance of “blue carbon” in the global C cycle, finding that these ecosystems capture up to 70% of organic C in the marine realm, rendering them one of the most efficient C sinks on the planet. Specifically, seagrass ecosystems are critically important to the global C cycle, and yet they are the least studied blue C ecosystem. Studies assessing C status and potential response to disturbances are essential for governing agencies who aim to develop management strategies to conserve and restore critical seagrass ecosystems. This research aims to fill this knowledge gap by quantifying C and nitrogen (N) stocks and fluxes in turtle grass (Thalassia testudinum, Banks and Sol. ex K. D. Koenig, 1805) meadows in the Lower Laguna Madre of South Texas, which have been experimentally subjected to anthropogenic disturbance from boat propeller scars. Soil and vegetation C and N pools within disturbed and nearby undisturbed areas will be estimated to determine the rate of post-disturbance changes of the historically sequestered C. I hypothesize that disturbed areas will show an increased rate of C loss from soils and coincident reduction of sequestered C and N, likely due to both erosion and microbial breakdown, and that regrowth of seagrass in these areas will be insufficient to return disturbed seagrass beds to pre-disturbance C levels. This study aims to provide the information needed to strike a balance between the growing population pressures that seagrasses face with the important ecological role of seagrass ecosystems to the global C cycle.


Copyright 2016 Alison Shepherd. All Rights Reserved.

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