Date of Award
8-1-2003
Document Type
Thesis
Degree Name
M.S. in Biological Science
Department
Biology
First Advisor
Dr. Stephen Threlkeld
Second Advisor
Dr. Clifford Ochs
Third Advisor
Dr. Lawrence Shaffer
Relational Format
Dissertation/Thesis
Abstract
This study was part of an EPA-funded experimental investigation of multiple stressor effects on agricultural wetlands. A 27-1 center point enhanced fractional factorial design was applied to 72 wetland mesocosms to examine 7 main effects and 21 two-way interaction effects (Montgomery 1997). Treatments included the agrichemicals monosodium methane arsenate (MSMA), chlorpyrifos and atrazine, inorganic nutrients (nitrogen, phosphorus, and silicon), the fathead minnow, suspended sediments (kaolinite), and UV radiation. Dissolved, suspended (sestonic), and periphyton C, N, and P, along with C:P, C:N, and N:P in each fraction were measured 2, 12, 24 and 48 days after treatments were added to the mesocosms. Periphyton pigments and phytoplankton pigments were examined to quantify changes in algal taxa. Of the 28 treatment effects evaluated, only dissolved nutrient responses were significant, and all involved dissolved P. The significant effects were due to nutrients, MSMA, the interaction of suspended sediments and UV, the interaction of atrazine and chlorpyrifos, UV, atrazine, and the interaction of atrazine and nutrients. Only the nutrient effect was found to influence nutrient ratios in dissolved, seston, and periphyton nutrients in a way that could be related to P. Nutrients, atrazine, and the interaction of nutrients and atrazine produced responses in phytoplankton, while MSMA, the interaction of atrazine and chlorpyrifos, UV, atrazine, and the interaction of atrazine and nutrients produced responses in periphyton. When principal components representing the seston and periphyton communities were plotted against nutrient ratio effects for all treatments, no robust indicator of response was found. Nutrient ratios do not appear to be consistent indicators of exposure to agrichemical, nutrient, UV and food web effects in simulated experimental wetlands. Only in specific cases, for example with nutrient and MSMA additions, were there correlations between nutrient ratios and responses in algal taxa.
Recommended Citation
White, William Robert, "Nutrient stoichiometry in algal responses to multiple stressors in experimental agricultural wetlands" (2003). Electronic Theses and Dissertations. 3433.
https://egrove.olemiss.edu/etd/3433