All ETDs from UAB

Advisory Committee Chair

R D Watson

Advisory Committee Members

Melissa Harris

Veena Antony

Chi-Ying Lee

Steven Watts

Document Type

Dissertation

Date of Award

2021

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Chemical dispersants are fast becoming the most widely used tool in the remediation of spilled oil. The sheer magnitude of the Deepwater Horizon oil spill necessitated the use of multiple forms of remediation at scales never attempted. As a result, there is a critical need to understand how the spill and ensuing cleanup efforts impacted the surrounding ecosystem and its inhabitants. The goal of this research is to better understand the impact of the chemical dispersant (Corexit®EC9500A) on a key ecological and economic species, the blue crab (Callinectes sapidus), in the Gulf of Mexico. The first part of my dissertation focuses on determining if exposure to Corexit® EC9500A affects the structure and function of gill epithelia. A 24-hour lethal concentration 50 (LC50) for Corexit®EC9500A was determined to be 210ppm. Histological analysis of gills exposed for 24-h to a sub-lethal concentration (125ppm) of Corexit®EC9500A revealed cellular degradation, cuticle loss, and fluid buildup in the hemolymph spaces. Quantitative image analysis revealed the area/length ratio of gill lamellae in exposed crabs was greater than that for control crabs. Quantitative PCR was utilized to measure the relative transcript abundance of three critical ion transport proteins (Na+/K+ ATPase, plasma membrane Ca2+ ATPase (PMCA), and sarcoplasmic reticulum/endoplasmic reticulum Ca2+ ATPase (SERCA)) in gills from Corexit-exposed and control crabs. The transcript abundance encoding each ion transport protein was significantly lower in gills from dispersant-exposed crabs than in gills from control crabs. The second part of my research focuses on elucidating the cellular mechanisms underlying the cytotoxic effects of Corexit® EC9500A. Results of immunohistochemical studies indicate that exposure to Corexit® EC9500A (125 ppm for 24 h) increased NADPH oxidase (NOX4), C-reactive protein (CRP), and cleaved (active) caspase-3 (CC3) immunoreactivity in gill lamellae. The final part of my research focuses on ascertaining if exposure to Corexit® EC9500A elicits a physiological stress response characterized by crustacean hyperglycemic hormone (CHH) mediated hyperglycemia. Exposure to a sub-lethal concentration of Corexit® EC9500A produced a transient (60 min) increase in hemolymphatic glucose, and a transient increase in abundance of the CHH transcript in eyestalk neural ganglia.

Share

COinS