Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Deborah MacLatchy

Advisor Role

Thesis Supervisor

Abstract

Since the late 1990s an investigation of cause (IOC) study at Irving Pulp and Paper Ltd (IPP), a bleached kraft mill in Saint John, NB, Canada, has successfully identified an in-mill waste stream (5th effect evaporator condensates) as containing endocrine disrupting substances (EDSs). These EDSs affect levels of reproductive steroids in a native estuarine fish, the mummichog (Fundulus heteroclitus). To confirm the minimal concentration at which whole condensates impact reproductive endpoints, adult mummichog were exposed to 2% and 4% (v/v) whole condensates for 14 days. Plasma testosterone was significantly depressed in males in the 4% (v/v) treatment, confirming previous work done with IPP condensates. Also, significant induction of hepatic cytochrome P450 genes 1 and 3 were found in female fish exposed to both condensate concentrations. To chemically isolate suspect EDSs, a solid phase extraction protocol was developed by collaborating researchers. The protocol generates four chemically-distinct fractions, along with residual condensates. Fractionation was completed using 4% (v/v) whole condensates and the resultant fractions, and 4% (v/v) whole condensates, were exposed to adult mummichog in the reproductive endocrine bioassay. There was no significant response in fish exposed to 4% (v/v) whole condensates, making interpretation of specific fraction treatments difficult. While fish were in different reproductive periods in the two bioassays, which may account for some of the differences between the experiments, a more compelling explanation is the variability in the chemical make-up of the condensates. Chemical fingerprinting of both condensate batches by collaborating researchers found a higher androgenic potency in the fractionation condensates. Mummichog were then exposed to model androgens methyltestosterone (100 and 1000 ng/L; MT) and dihydrotestosterone (10 and 100 μg/L; DHT) to determine if androgenic responses paralleled condensate responses. Plasma testosterone was significantly depressed by 10 μg/L DHT in males. Females had significant depression of plasma estradiol when exposed to both DHT concentrations and 1000 ng/L MT. Female mummichog had lower thresholds of effects than males and were more responsive to androgen exposure. Comparison of effects seen in fish exposed to pulp mill condensates and those exposed to model androgens indicate androgens in the condensates may not be the source of reproductive endocrine effects in the condensate-exposed mummichog.

Convocation Year

2011

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