ABSTRACT
Introduction ................................................................................................................................. 134 Methods ........................................................................................................................................ 138
Study Sites ........................................................................................................................ 138 Sampling of Sediments, Plants, and Animals for Oil Contamination ..................... 140 Comparison of Marsh Oil with Macondo Oil ............................................................. 141 Plant Stress Responses .................................................................................................... 141
Pulsed Amplitude Modulation Chlorophyll Fluorescence ........................... 142 LI-COR Chlorophyll Fluorescence and Gas Exchange .................................. 143
Statistical Analyses .......................................................................................................... 143 Results ........................................................................................................................................... 144
Spatial Contamination .................................................................................................... 144 Time-Series Contamination ........................................................................................... 144 Photosynthesis Responses to Oil Contamination ....................................................... 150
Pulsed Amplitude Modulation Chlorophyll Fluorescence at Marsh Point ............................................................................................. 150 LI-COR Fluorescence and Gas Exchange at Marsh Point ............................. 151
One-Year Assessment ..................................................................................................... 155 Discussion .................................................................................................................................... 155
Contamination ................................................................................................................. 155 Location-Specific Oil Impacts ........................................................................................ 159 Acute and Chronic Photosynthesis Responses ........................................................... 161
Conclusions .................................................................................................................................. 164 Acknowledgments ...................................................................................................................... 164 References ..................................................................................................................................... 164
The Deepwater Horizon (DWH) explosion and subsequent oil spill in the northern Gulf of Mexico (GOM), from April 20 to July 15, 2010, is the largest accidental marine oil spill in the history of the U.S. petrochemical industry (Read 2011). This accident released about 4.9 million barrels (7.0 × 106 m3) of crude oil into the open ocean from the leaking Macondo (MC252) well at 1.5 km depth (Crone and Tolstoy 2010) and at approximately 170 km from the Mississippi mainland coast. Salt marshes are important coastal ecosystems because they are highly productive. They also provide valuable ecosystem services, such as the provision of food and shelter for many organisms (Turner 1977; Boesch and Turner 1984; Phillips 1987; Cai et al. 2000; Beck et al. 2001), carbon sequestration (Chmura et al. 2003), shoreline stabilization and storm protection (King and Lester 1995; Moeller et al. 1996), filtration of excess nutrients (Valiela et al. 2000; Tobias et al. 2001a,b; Valiela and Cole 2002), and valued recreational and aesthetic opportunities (Lee et al. 1992; Engle 2011; Jordan and Peterson 2012). Coastal wetlands are not only threatened by stressors from the terrestrial side (sensu Peterson and Lowe 2009), but are also at risk from ocean-side stressors that include pollutants such as oil.
