Dissertations, Theses, and Capstone Projects

Date of Degree

6-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Earth & Environmental Sciences

Advisor

Peter Groffman

Advisor

Shakila Merchant

Committee Members

William Hernandez

Reginald Blake

Meagan Eagle

Subject Categories

Biogeochemistry | Climate | Earth Sciences | Environmental Monitoring | Environmental Sciences

Keywords

Blue Carbon, Mangorves, Heavy Metals, Contamination, Climate Change, Remote Sensing, Puerto Rico, Caribbean

Abstract

Mangrove ecosystems provide essential ecological services, including carbon sequestration, coastal protection, and heavy metal retention. However, their resilience and functionality are increasingly influenced by hurricanes, climate variability, and anthropogenic contamination. This dissertation integrates three research efforts examining mangrove canopy dynamics, carbon storage, and heavy metal contamination in two Puerto Rican mangrove systems: La Parguera and Laguna Grande.

Using remote sensing techniques (LiDAR and NDVI analysis), we assessed the impact of Hurricane Maria (Category 4, 2017) on mangrove canopy structure and vegetation health. Results revealed significant canopy height loss, with greater damage at Laguna Grande, where pre-storm canopy height and human disturbances influenced post-hurricane recovery. These findings highlight the value of remote sensing for assessing mangrove resilience and regeneration following extreme climatic events.

Analysis of carbon storage showed that hydrology and sedimentation play key roles in regulating blue carbon stocks. Despite its higher precipitation and temperature, Laguna Grande stored more carbon (166 ± 66 Mg C ha⁻¹) than La Parguera (115 ± 68 Mg C ha⁻¹), likely due to restricted tidal exchange and greater primary production. In contrast, La Parguera’s stronger tidal flushing may enhance organic matter export, reducing long-term carbon retention. These findings underscore the importance of hydrological processes in blue carbon dynamics and the need to integrate geomorphological and climate-driven factors into mangrove conservation strategies.

Heavy metal analysis revealed higher concentrations of arsenic, cadmium, chromium, copper, nickel, lead, and zinc at Laguna Grande, likely due to anthropogenic inputs. Metal retention and bioavailability varied between sites: La Parguera exhibited greater plant-mediated stabilization of metals such as zinc and lead, potentially reducing immediate bioavailability, whereas Laguna Grande showed higher bioavailability of cadmium and nickel, increasing the risk of biological uptake and ecosystem stress. Additionally, metal-carbon interactions differed between sites, suggesting that sediment carbon content may influence metal behavior and serve as an indicator of contamination sources.

Collectively, these findings highlight the complex interactions between extreme weather events, hydrology, biogeochemical cycling, and pollution in shaping mangrove ecosystem function. Understanding these processes is critical for developing targeted conservation and management strategies to enhance mangrove resilience, mitigate climate change impacts, and sustain vital ecosystem services.

Download

This work is embargoed and will be available for download on Wednesday, June 10, 2026

Share

COinS