The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type


Degree Name

Biological Sciences - Cell and Molecular: M.S.




College of Science and Engineering

First Advisor

Heiko Schoenfuss

Second Advisor

Jessica Ward

Third Advisor

Mark Mechelke

Fourth Advisor

Paige Novak

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Keywords and Subject Headings

Climate Change, Endocrine Disruption, Behavior, Life Stage, Fathead Minnow


Human-mediated environmental impacts can induce changes in the expression of complex behaviors within individuals, and alter the outcomes of interactions between individuals. Although the independent effects of a number of important stressors on aquatic biota are well documented (e.g., exposure to environmental contaminants), fewer studies have examined how natural variation in the ambient environment modulates these effects. In this study, factorial experiments were conducted to assess the influences of temperature and estrogen concentration on two life stages of fathead minnow (Pimephales promelas). Larval and adult minnows were exposed for 21 or 30 days, respectively, to 3 concentrations of estrone (nominally at 25, 125, and 625 ng/L) or to an ethanol carrier control (0 ng/L), at four water temperatures (15, 18, 21, and 24 °C) reflecting natural seasonal variation. A series of behavioral experiments were conducted to assess the independent and interactive effects of temperature and estrogen exposure on intra- and interspecific interactions in three contexts with important fitness consequences (i.e., reproductive behavior, foraging, and predator evasion). In addition, a series of anatomical and physiological endpoints were explored to assess the independent and interactive effects of chemical exposure on plasma vitellogenin induction, blood glucose, hematocrit, histology, and morphometric indices. Evidence was obtained suggesting that thermal regime can modulate the effects of exposure on larval survival, larval predator-prey interactions, and adult physiological and anatomical endpoints, even within a relatively narrow range of ambient temperatures. These findings improve our understanding of the outcomes of interactions between anthropogenic stressors and natural abiotic environmental factors, and suggest that such interactions can have ecological and evolutionary implications for freshwater populations and communities.


For my Grandmom, who taught me I could be both strong and kind.

For my parents, I hope I make you proud.

And to my advisors and greatest mentors, Dr. Jessica L. Ward and Dr. Heiko L. Schoenfuss, whom without I may never have come this far, thank you for encouragement and your guidance.



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