Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Dr. Jim McGeer

Advisor Role

Supervisor

Abstract

The mechanisms behind metal-metal interactions in freshwater environments are currently not well understood. Freshwater environments consist of many different types of metals, from those naturally present such as copper (Cu) and those that originate from anthropogenic sources like silver (Ag). Both Cu and Ag use apical sodium (Na+) channels for uptake into the gills of freshwater fish. In the gills, the mechanisms of Cu2+ and Ag+ toxicity appear to be similar to one another, which is by inhibiting Na+ /potassium (K+)- adenosine triphosphatase (NKA) and carbonic anhydrase (CA). Inhibition of NKA and CA results in ionoregulatory disturbances where branchial Na+ and chloride (Cl-) uptake is reduced and can result in mortality. The overall goal of this research was to build a better understanding of the interactions between Cu and Ag in the context of sub-chronic impacts of metal mixtures on the rainbow trout (Onchorhynchus mykiss). Juvenile rainbow trout were exposed for 10 and 14 days to Cu-only (10-day: 1.0 µM Cu2+, 14-day: 0.35 µM Cu2+), Ag-only (0.04 µM Ag+) or a Cu 2+ + Ag+ mixture (10-day: 1.0 µM Cu2+ + 0.04 µM Ag+; 14-day: 0.35 µM Cu2+ + 0.04 µM Ag+). The effects of Cu-Ag interactions were assessed by measuring bioaccumulation in whole gill, liver and kidney samples, subcellular distribution in the gills and liver, and plasma Na+ and Cl- content. Mortalities were dose dependent and greatest in the mixture exposures. Significant accumulation of Cu and Ag in the gills and kidney were a result of a more than additive affect by metal interactions. Cu accumulation in the liver was also more than additive but no effect was observed on hepatic Ag. Subcellular distribution of Cu mainly occurred in metal sensitive fractions (MSF) while Ag accumulated mainly in biologically detoxified fractions (BDF). Fish exposed to the mixture for 10-days experienced more than additive disruption in plasma Na+ but not in plasma Cl-. During 14-days, mixture-exposed fish experienced a more than additive disruption on ion regulation where plasma Na+ and Cl- were significantly less than Cu2+ or Ag+-only exposed fish. Overall, the effects of metal interactions on bioaccumulation, physiological effects and mortalities were based on exposure concentration.

Convocation Year

2016

Convocation Season

Spring

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