Abstract
Coastal ecosystems are greatly endangered due to anthropogenic development and climate change. Multiple disturbances may erode the ability of a system to recover from stress if there is little time between disturbance events. We evaluated the ability of the saltmarshes in Barataria Bay, Louisiana, USA, to recover from two successive disturbances, the DeepWater Horizon oil spill in 2010 and Hurricane Isaac in 2012. We measured recovery using vegetation indices and land cover change metrics. We found that after the hurricane, land loss along oiled shorelines was 17.8%, while along oil-free shorelines, it was 13.6% within the first 7 m. At a distance of 7–14 m, land loss from oiled regions was 11.6%, but only 6.3% in oil-free regions. We found no differences in vulnerability to land loss between narrow and wide shorelines; however, vegetation in narrow sites was significantly more stressed, potentially leading to future land loss. Treated oiled regions also lost more land due to the hurricane than untreated regions. These results suggest that ecosystem recovery after the two disturbances is compromised, as the observed high rates of land loss may prevent salt marsh from establishing in the same areas where it existed prior to the oil spill.
Highlights
Coastal deltas, including the Mississippi River Delta, are affected by high rates of land conversion, subsidence and anthropogenic use [1,2]
We focus on assessing the effect of two sequential disturbances, the Deepwater Horizon (DWH) oil spill and Hurricane Isaac, on the recovery potential of coastal wetlands in the Mississippi Deltaic Plain (MDP)
We focused on Barataria Bay (Figure 1) because it was severely impacted by both the oil spill and Hurricane Isaac, and we used airborne imagery (Advanced Very High Resolution Image Spectrometer (AVIRIS)) over this area soon after the oil spill in September 2010, a year later in August 2011 and post-hurricane in October 2012
Summary
Coastal deltas, including the Mississippi River Delta, are affected by high rates of land conversion, subsidence and anthropogenic use [1,2]. Hydrologic changes in the MDP in recent decades reduced sediment supply because of damming of the Mississippi. Freshwater wetlands experienced high rates of mortality due to saltwater intrusion after construction of deep navigational channels into the delta, and coastal wetlands have experienced direct loss due to dredging for pipelines [8,10,11,12], oil extraction and spills [13,14]. As a result of the reduction in sediment supply and the loss of top soil in lost wetland areas, the MDP erosion rate is ~50 km2 ·year−1 [7,8,11]. We focus on assessing the effect of two sequential disturbances, the DWH oil spill and Hurricane Isaac, on the recovery potential of coastal wetlands in the MDP
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