COS 94-1
Evaluating impacts of the 2010 Macondo oil spill on Louisiana coastal marshes using Landsat data
Coastal ecosystems face a variety of threats ranging from global climate change to regional human intervention. Coastal marshes in Louisiana are inherently vulnerable to such threats because they are microtidal and inhabit a narrow portion of the intertidal zone. The 20 April 2010 Macondo oil spill, the largest accidental marine oil spill in recorded history, may pose a serious threat for Gulf of Mexico coastal ecosystems. This study investigated the impact of the Macondo oil spill on Louisiana coastal marshes. The study area was in the Barataria Basin of southeastern Louisiana, where large amount of oil was found in the months after the oil spill. We selected locations of heavily oiled sites and sites without oil based on the Shoreline Cleanup and Assessment Technique ground surveys performed in 2010. We acquired and processed Landsat imagery to produce Normalized Difference Vegetation Index (NDVI) data for the years 2009, 2010, and 2011, to compare the marsh vegetation conditions before and after the oil spill. Landsat imagery processing was performed using ENVI 4.8 software. ANCOVA was conducted using SAS 9.4 software.
Results/Conclusions
In 2009, a reference year for marsh spectral response before the oil spill, NDVIs of the study sites were similar. In 2010, the year of the oil spill, NDVIs of heavily oiled sites were significantly lower than those of sites without oil (p=0.0006). In the following years, 2011, the oil effect was still significant (p=0.0025).This does suggest that the oiled marshes did sustain some damage from oiling for two years, at least, whether directly on physiological functioning and/or the covering of culms, limiting near-infrared reflectance and photosynthetic activity. In addition, literature has suggested that it would take more than two years to document the effects of heavy oiling on the marsh shoreline. Therefore, future remote sensing investigations of the impacts of the Macondo oil spill on Louisiana coastal marshes will require a longer time frame.