Honors College Capstone Experience/Thesis Projects

Department

Biology

Additional Departmental Affiliation

Public Health

Document Type

Thesis

Abstract

Amphibian populations have been experiencing rapid declines worldwide in the past few decades. There are many proposed causations, including the use of agricultural chemicals such as herbicides. Glyphosate based herbicides are one of the most widely used herbicides. This study looks at the effects of different brands of glyphosate-based herbicides, including those intended for aquatic use, on the survival and growth of axolotl salamander larvae. Out of four brands of glyphosate herbicide (Aquamaster, Aquaneat, Helosate plus, and Roundup Pro), the survival rates of Roundup Pro were the lowest. Most mortality occurred between the 3 mg/L and 6 mg/L concentrations, during which all those treated with Roundup Pro died. The growth, measured in terms of total snout to tail length and head width, appeared to be greatest in length for those larvae treated with Aquaneat brand herbicide. These results indicate that Roundup Pro is lethal at concentrations of 6 mg/L, and that the composition, which includes the surfactant POEA, may be responsible. Subsequently, the concentration at which different adjuvant surfactants meant for use with aquatic safe herbicides (Dyne-Amic, Kinetic, and Cygnet) affected larval growth and survival was compared to the results obtained with Roundup Pro. The larvae exposed to the initial 5 mg/L concentration of Roundup Pro had total mortality, but survival was unaffected by exposure to aquatic safe surfactants at low concentrations. At high concentrations, Dyne-Amic and Kinetic significantly increased larval mortality while Cygnet did not. Of the surviving larvae, there was no difference in growth. The findings of this study are significant in that they give insight regarding how the use of herbicides could be contributing to the decline of amphibian populations.

Advisor(s) or Committee Chair

Dr. Jarrett Johnson

Disciplines

Animal Experimentation and Research | Biology | Environmental Health | Toxicology

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