Pesticides are used primarily for agricultural purposes in the US and while these chemicals provide many benefits, the inherent toxicity of the compounds pose a substantial risk to the environment. These chemicals may enter water bodies in areas with a high proportion of agricultural land use through surface run off, ground water discharge, and erosion, and negatively impact non-target aquatic organisms. As a result, Louisianas estuaries may be vulnerable to a variety of compounds, including the herbicide atrazine. Atrazine is used extensively throughout the Midwest and has been known to enter the Mississippi River through surface runoff and ground water discharge. The River transports the compound downstream to the delta, where it is discharged into Louisianas coastal estuaries. Due to the high amount of sugarcane production in the southeastern part of the state, atrazine also has the potential to enter these systems indirectly through agricultural runoff, and adversely affect native aquatic organisms. Because it is a photosynthesis inhibitor, phytoplankton communities may be especially susceptible to atrazine exposure. The phytoplankton stress response in these systems may be critical because phytoplankton form the base of the food web and are essential to the production of the entire ecosystem. The purpose of this study was to determine the extent of atrazine contamination in Louisianas estuaries, and its effect on local phytoplankton stress response. Field samples were taken under low and high flow and nutrient conditions from Breton Sound and Barataria Estuary. The results showed that atrazine was consistently present in these systems at low levels. Local phytoplankton from Barataria Estuary were also grown in microcosm and exposed to an atrazine dilution series under low and high nutrient conditions to determine the phytoplankton stress response. The treatment groups that received 5 ppb and 50 ppb atrazine treatments under high nutrient conditions exhibited an extended lag phase and entered into the exponential growth phase several days after the control groups. Overall, communities in nutrient enriched treatment groups exhibited higher growth response, oxygen production, and were healthier than non-enriched groups, indicating that atrazine exposure may induce a stress response in phytoplankton communities under low nutrient conditions.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-05292015-181515 |
| Date | 10 June 2015 |
| Creators | Starr, Alexis Victoria |
| Contributors | Bargu, Sibel, Wilson, Vincent, Delaune, Ronald, Johnson, Crystal |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-05292015-181515/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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