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Evaluating oil spill effects and restoration potential of Alabama salt marshes using experimental wetlands Thomas Hess and Christopher J. Anderson School of Forestry and Wildlife Sciences Auburn University Alabama Water Resource Conference 5 September 2013 Slide 2 2010 Deepwater Horizon Oil Spill ~4.5 million barrels of oil spilled in May 2010 Impacted coastal areas without a history of oil spills from petroleum production Some exposure to Alabama salt marshes Slide 3 2011 Mesocosm Research Goals Research Goals: Determine how Juncus roemerianus marshes responds to dose and weathered condition of oil Slide 4 2011 Mesocosm Methods 32 wetland mesocosms were developed using Juncus sod and designed to mimic tides 3 dose treatments Low (6 L /m 2 ) Medium (12 L /m 2 ) High (24 L /m 2 ) 3 weathering treatments None (full strength) 3 days 3 weeks Oil was applied to wetland mesocosms in July 2011 Slide 5 2011 Mesocosm Methods Slide 6 July 16 Sep 1 Aug 4 2011 Mesocosm Results Slide 7 Mean (SE) percent no. of live stems compared to pre-oil count a a a b a a b b c b bc c 2011 Mesocosm Results Stem survival (Dose) Slide 8 Mean (SE) percent no. of live stems compared to pre-oil count a a a b bb b b b b b b 2011 Mesocosm Results Stem survival (Weathering) Slide 9 Mean (SE) percent photosynthesis rate compared to control a a a a b b NS b a ab 2011 Mesocosm Results Photosynthetic rate Slide 10 2012 Microcosm Research Goals Research Goals: Determine how amenable salt grass (Distichlis spicata) would be for remediation of oiled marshes. Slide 11 2012 Microcosm Project Continuation of the mesocosm study aimed at determining the restoration potential of salt grass (Distichlis spicata) on oiled marshes. Potential bioremediation: Improved degradation of subsurface oil through root aeration of soil. Reducing coastal erosion by re-establishing a root matrix. Slide 12 2012 Microcosm Methods 84 marsh plugs from the 2011 mesocosm experiment Used 2011 dosage treatments: Control Low Medium High Hoses and drip irrigation valves used to recreate tidal fluctuations Slide 13 2012 Microcosm Methods Planted- September 4, 2012 Half of the pots were fertilized- September 18, 2012 Pulsed with 50 gallons of brackish water two to three times a week Stem counts and heights were taken once every three weeks Final plant heights and biomass measured- December 17, 2012 Fig. 6 Slide 14 Total Petroleum Hydrocarbons (TPH) Average TPH concentration for microcosms based on analyses in June 2012 (n=24) and December 2012 (n=18) Slide 15 2012 Microcosm Results Influence of oil on stem heights Slide 16 2012 Microcosm Results Influence of oil on stem counts Non-Fertilized Slide 17 2012 Microcosm Results Aboveground plant biomass NS a b b b Non-Fertilized Fertilized Slide 18 2012 Microcosm Results Final plant biomass FertilizedNon-Fertilized a b ab NS n=8 n=4 Slide 19 Summary 2011 Mesocosm Study Oil had a negative effect on stem survival High dose wetlands had the most rapid decline in survivorship Weathering seemed to have little effect on Juncus Oil exposure had a negative effect on plant photosynthetic rates Four weeks after application Slide 20 Summary 2012 Microcosm Study Soil TPH was substantially lower than concentrations in the 2011 study Combination of lower soil TPH, and fertilizer produced the most grass stems Control microcosms tended to produce greater below ground biomass Slide 21 Questions Slide 22 Mean (SE) CO2 uptake rate per mesocosm a b b b NS b bc c aa b c c 2011 Mesocosm Results CO 2 uptake rate Slide 23 2012 Microcosm Results Final plant biomass Slide 24 2012 Microcosm Results Root to Shoot Ratio