Date of Award

5-2007

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry

Advisor

Gregory D. Mayer

Second Committee Member

Rebecca van Beneden

Third Committee Member

John P. Wise, Sr.

Abstract

The future of the Gulf of Maine Atlantic salmon (Salmo salar) population is in dire straits and is largely dependent upon habitat restoration. One factor that is known to contribute to the decline of Atlantic salmon populations is lack of access to quality spawning areas upstream of dams. Two dams that hinder salmon migration have been slated for removal from the Penobscot River near Bangor, Maine, in an effort to revive the endangered Gulf of Maine Atlantic salmon population as part of the Penobscot River Restoration Project. Due to mechanical perturbation of downstream sediments, dam removal can result in release of sediment-bound toxicants into the river water column. This potential desorption of toxicants could increase bioavailability of sediment-bound toxicants and induce deleterious effects in aquatic species associated with the perturbed water column. We hypothesize that desorbed contaminants following sediment resuspension will not elicit deleterious biological responses to aromatic hydrocarbons, estrogens, and heavy metals. Multiple biomarkers were analyzed in vivo and in vitro in an effort to characterize potential toxicity of sediment resuspension following dam removal. Adult and embryonic zebrafish (Danio rerio) were exposed to river water resuspended with sediments downstream of dams slated for removal and analyzed for transcription of CYP1A1 and vitellogeninl genes using fluorescence-based qRT-PCR. Embryonic zebrafish were exposed to resuspended water and analyzed for transcription of metallothionein using fluorescence based qRT-PCR. These three bioindicators are indicative of exposure to aromatic hydrocarbons, estrogens, and heavy metals, respectively. The presence of estrogen receptor agonists in the resuspended water was analyzed utilizing an estrogen-induced, cell-based, transcriptional assay incorporating luciferase as a reporter gene. Additionally, transgenic zebrafish embryos possessing the green fluorescent protein reporter gene downstream of metal responsive elements were exposed to resuspended sediment water to elucidate metal response. Results indicate that sediment contaminant desorption following Penobscot River dam removal may elicit minimal biological response in fish species. Larval zebrafish 84-108 hours post fertilization (hpf) exhibit transiently elevated CYP1 Al expression following exposure to resuspended river water. Bioindicators suggest that potential desorption of estrogenic compounds and metals from river sediment do not elicit a biological response in fish. Complex interactions between various compounds in the aquatic environment necessitate the use of multiple bioindicators to determine biological response to changing habitat conditions. Analysis of potential toxicant release prior to dam removal will help direct remediation efforts within the overall restoration plans to reduce biological effects on fish species.

Share