Date of Award

12-31-2018

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences/Environmental, Earth & Ocean Sciences

First Advisor

Helen C. Poynton

Second Advisor

William E. Robinson

Third Advisor

Robert E. Bowen

Abstract

Endocrine Disrupting Compounds (EDCs) are ubiquitous in marine environments and have been found to cause intersex and developmental impacts across wildlife species including mussels. Innovative approaches are needed to monitor EDCs in coastal environments as these compounds cause effects at low levels (e.g., ng/L), and below analytical detection limits. Additionally, a comprehensive literature search identified at least a hundred compounds that produced an estrogenic response, making monitoring individual contaminants both time and cost intensive. The purpose of this research was to develop a high throughput assay and adverse outcome pathway (AOP) to monitor the exposure and effects of EDCs in coastal environments in marine mussels. Although intersex from EDC exposure has been identified in bivalves, the mechanism linked to this adverse outcome is relatively unknown. A combination of transcriptomic analysis followed by systems biology and computational approaches identified the non-genomic estrogen signaling pathway and steroidogenesis pathway as the likely mechanisms of adverse action. A putative AOP and mechanism-based biomarkers representative of key events (KE) were developed to form the Coastal Biosensor of Endocrine Disruption (C-BED) assay. The C-BED assay was validated in the lab over multiple time-points and was found to respond at the most contaminated field locations in both a native and transplanted mussel study. Adverse effects on reproduction and development were suggested by induction of female specific transcripts in both male and female mussels and delayed development in EDC treatments. In addition to the C-BED assay, this research also showed several promising gene expression applications for biomarker development. First, a novel mtDNA sex identification assay was developed that may be a time and cost-effective alternative to other gender identification methods. Secondly, candidate biomarkers for different contaminants were identified by correlating bioaccumulation in mussel deployed in the Boston Harbor with gene expression data. Finally, the C-BED assay combined with the Integrated Biomarker Response (IBR) also proved to be a reliable method to rank EDC exposure. This study can therefore be used as an example of how transcriptomics and various data analysis approaches can be used to develop novel biomarkers for organisms that lack annotated regulatory and biochemical pathways.

Comments

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