Master of Science (MS)
Abstract The aim of this study was to determine the impacts of the Deepwater Horizon (DWH) oil spill on the common reed Phragmites australis, and the processes controlling species effects and recovery, via a greenhouse mesocosm study. In the greenhouse DWH source oil, weathered approximately 40% by weight and emulsified, was applied to the aboveground shoots of P. australis growing in marsh sods to produce the following treatment-levels: (1) oil coverage of the lower 30% of shoot-height, (2) the lower 70% of shoot-height, (3) repeated oil coverage of the lower 70% of shoot-height, (4) 100% oil coverage of shoots, (5) oil applied to the soil at a rate of 8 L m⁻², and (6) unoiled controls. I quantified a strong resilience of P. australis when oil was applied only to aboveground biomass, with negative impacts becoming apparent when oil was added to the soil profile. The Total biomass and stem cumulative length were both impacted by the addition of 8 L m⁻² of weathered DWH source oil to the soil profile. Due to the apparent negative results of adding oil directly to the soil, a second experiment was designed to better understand impacts from soil oiling. Aboveground biomass was harvested from the sods that had received only shoot oiling and allowed to regrow for two months, at which point weathered DWH source oil was applied to the marsh sods at rates of (1) 0 L m⁻² (control), (2) 4 L m⁻², (3) 8 L m⁻², (4) 12 L m⁻², and (5) 16 L m⁻². This experiment verified that increased oiling to the soil profile increased negative impacts to P. australis, reducing stem cumulative length, aboveground biomass, and belowground biomass at the highest oiling rates. Higher oiling doses resulted in higher rates of soil respiration and reduced soil Eh. Based on my research, complete mortality of P. australis is unlikely from exposure to weathered and emulsified DWH source oil. However, vertical growth, above and belowground biomass, and other plant processes will be impacted, with oiling to the soil having much greater impact than oiling to the aboveground shoots.
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Judy, Chad Robert, "Impacts and recovery of the Deepwater Horizon oil spill on vegetation structure and function of Phragmites australis" (2013). LSU Master's Theses. 170.