Date of Award

Spring 5-10-2021

Document Type

Honors Thesis



First Advisor

Jacob Kerby, Ph.D.

Second Advisor

Jeff Wesner, Ph.D.

Third Advisor

Christopher Anderson, Ph.D.


selenium, tile drains, painted turtles, wetland, bioaccumulation

Subject Categories

Biology | Terrestrial and Aquatic Ecology


Tile drain systems are a critical advancement in agriculture that move excess water from crop fields to streams, ditches, and wetlands. Selenium is a necessary mineral but is considered toxic at high levels. Previous research indicates that wetlands with tile drains are at a higher risk for elevated selenium concentrations. Selenium enters the aquatic ecosystem via these tile systems and us taken up by invertebrates and continues to bioaccumulate mainly via direct transfer in higher trophic level taxa such as fish, amphibians, reptiles, birds, and mammals. For this study, painted turtles (Chrysemys picta) served as a model organism to detect selenium levels in higher trophic level organisms. I hypothesized that tile site turtles’ blood level selenium concentration would be higher compared to the control site turtles. During the summer of 2019, I collected water and turtle blood samples from four control (relatively pristine wetlands with no direct input of contaminants) and four tile wetland (wetlands with a direct input of contaminants from a tile drain) sites. Turtle blood samples were collected from fifteen control and nineteen tile sites (n=34). There was a positive correlation between water and blood selenium concentrations. I estimated a >99.99% probability that tile wetlands will have greater water selenium concentrations and a 99.8% probability that tile site turtles will have greater selenium concentrations in their blood compare to control site turtles. The average blood selenium concentration for tile turtles was 3.56 μg/L while control site turtles’ average was 0.50 μg/L. Finally, there was also a positive correlation between turtle mass and blood selenium concentration. These elevated levels of selenium in tile wetlands are of great concern as they are potentially threatening the health of these wetland ecosystems and these turtles specifically.



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