Impact and Recovery of Ecologically and Hydrologically Diverse Wetlands after the BP Deepwater Horizon Oil Spill in the Gulf of Mexico

Abstract:

April 20, 2010 marked the start of the British Petroleum Deepwater Horizon Oil Spill, the largest oil spill in US history, which contaminated the coastal wetland ecosystems along the northern Gulf of Mexico. We used NASA airborne AVIRIS imagery and field surveys to determine the impact and recovery of three ecologically and hydrologically diverse ecosystems after the oil spill using data acquired in 2010, 2011 and 2012. This was the largest campaign attempted at that time, collecting 456 AVIRIS flightlines between 6 May and 4 Oct., 2010, many covering the coastal region impacted by the oil spill. We investigated Barataria Bay (an intertidal saltmarsh ecosystem, predominantly a Spartina-Juncus meadow), East Bird’s Foot (the most botanically diverse wetland, is an intermediate/freshwater marsh, fed by the Mississippi River), and Chandeleur Islands (barrier islands surrounded by tidal mangrove shrublands). A comparison of the three sites showed variable impacts from the oil and differential ecosystem recoveries. Mangroves around the Chanderleur Islands were the most adversely affected by the oil spill and showed the least recovery after a year, based on spectral changes characteristic of stressed vegetation. East Bird’s Foot freshwater marshes were minimally affected by the spill and it is likely that the Mississippi outflow resulted in little crude oil reaching these shorelines. A zonal analysis of Barataria Bay revealed that oil primarily impacted the intertidal zone along shorelines that faced the Gulf, with little impact of the oil after an average distance of 20m inland, approximately the height of the highest high tides. Although recovery of the saltgrass meadow was robust during the first year after the spill, it was also variable, with the 5m zone immediately inland from the shoreline showing the least recovery. Hurricane Isaac in 2012, although a mild category 1 hurricane, adversely impacted the saltgrass meadows along the shorelines that were recovering from the oil spill, which after the hurricane showed reduced growth compared to shorelines that were not damaged by the 2010 oil spill.