Multi-scale Modeling Dynamics of Marine Populations with Implications for Ecosystem Management of the Northern Gulf of Mexico

Abstract

The U.S. northern Gulf of Mexico (GoM) coastal waters provide invaluable ecosystem functions and services for human welfare. However, GoM ecosystems have been disrupted by decades of anthropogenic activities in conjunction with climate change. While understanding anthropogenic and climate-induced impacts has become a consensus towards ecosystem-based management, the obstacle that lies ahead is how to tease apart confounding interactions in ecosystem dynamics. This dissertation used multi-scale modeling approaches to address existing challenges in understanding ecosystem dynamics in the GoM. This dissertation begins with a large-scale population study focusing on the bloom dynamics of jellyfish (Aurelia spp.) over the GoM continental shelf from 1995 to 2010. The spatio-temporal variations in jellyfish abundance and biomass were simulated by using an Individual-Based Model (IBM). The model simulation disclosed the potential bloom areas including coastal waters off South Texas, East Louisiana, and nearby the Mississippi Sound, driven by distinct oceanographic processes. In addition, the statistical analysis based on model simulation highlighted the bottom-up effects of zooplankton on triggering GoM jellyfish outbreaks. The second focus of this dissertation tackles a problem in understanding the recruitment dynamics of oysters in response to hurricane disturbance at the estuarine scale. Specifically, a Dynamic Energy Budget Model (DEBM) was applied under “post-hurricane” and “baseline” scenarios to partition the relative impacts of hurricanes on the recruitment of planktonic oyster larvae in the Galveston Bay System. The results indicated a strong post-disaster resilience of oyster larvae. Salinity had profound effects on oyster larval recruitment shaping the spatial patterns of recovery. The planktonic habitat suitability model for oyster larvae showed the optimal habitats in lower Galveston Bay and West Bay and the least optimal habitats in upper Galveston Bay and East Bay. The third focus of this dissertation was given to identifying underlying mechanisms by which humans act on estuarine ecosystems under climate change. Specifically, an Empirical Dynamic Modeling (EDM) approach was used to study the dynamics and stability of two biogeographically similar estuarine systems in Texas with different levels of urbanization. The results highlighted the role human plays in magnifying the fluctuation in biological populations and decoupling interspecies interaction. Although human intervention destabilized the ecosystem, making it vulnerable to climate change, biodiversity and species interaction exerted buffering effects to maintain ecosystem functions and services. Overall, this dissertation highlights the utility of heuristic modeling approaches in multi-scale ecological studies ranging from estuaries to coastal waters, and from populations to an ecosystem. The findings of this dissertation contribute to the assessment and management of estuarine and coastal marine ecosystems subjected to human and natural disturbances in the face of climate change.