Date of Graduation

2018

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Patricia M Mazik

Committee Co-Chair

Vicki S Blazer

Committee Member

Jim D Hedrick

Committee Member

George T Merovich

Committee Member

Amy B Welsh

Abstract

The Potomac River is a large tributary of the Chesapeake Bay. Large fish die-offs were reported in the Potomac watershed (specifically the South Branch of the Potomac) in 2002 and 2005, as well as smaller episodic events in recent years which have no clear correlation to any one pathogen or contaminant. Although a variety of pathogens have been identified (such as trematodes, myxozoans, Aeromonas hydrophila, A. salmonicida, Flavobacterium columnare , and largemouth bass virus) in recent die-offs of smallmouth bass Micropterus dolomieu, no clear cause has been derived. Additionally, reproductive endpoints were reported in smallmouth bass and likely associated with instream estrogenic compounds. There has been increasing support for estrogenic compounds associated with agricultural runoff as one of the causes. However, there are little data on the contribution from primary producers such as cyanobacteria. Harmful algal blooms are of increasing concern to human health worldwide and their effects on the aquatic community within the South Branch Potomac watershed is largely unknown. To address knowledge gaps associated with fish health in the South Branch Potomac watershed, an assessment of the temporal and spatial distribution of algal toxins and environmental estrogens was required. This dissertation addresses: 1) the spatial and temporal distribution of cyanobacterial toxins in water, periphyton, and fish tissue; 2) the transcriptional response of smallmouth bass hepatocytes and leukocytes challenged with the cyanobacterial toxin microcystin-LR; 3) the spatial and temporal distribution of environmental estrogens in water and periphyton and their association with phytoestrogen presence and cyanobacterial toxins; and 4) an assessment of reporter interference in water and periphyton samples.

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