Overview of Research into the Coastal Effects of the Macondo Blowout from the Coastal Waters Consortium: A GoMRI Consortium

Abstract

ABSTRACT The Coastal Waters Consortium (CWC) led by Louisiana Universities Marine Consortium is one of eight Gulf of Mexico Research Initiative research consortia. The CWC focuses on: oil transport and fate, chemical evolution and biological degradation, and environmental effects.The following is an overview of a portion of the research conducted within the consortium. The consortium works in a system that was impacted by the Deepwater Horizon oil disaster and additionally impacted by freshwater diversions resulting in changes in salinity, tropical storms, and hurricanes. First, we conducted model simulations assessing oil transport into the Barataria Bay estuary, which indicate that easterly winds and feeding of the anticyclonic gyre in the Louisiana Bight pushed the oil into Barataria Bay. In subtidal sediments adjacent to oiled marshes, marsh detritus from eroding marsh edges eventually became entrained in the sediment column. Biotic impacts vary. The above-ground plant biomass appears healthy at the individual sampling sites; overall the most seaward (i.e., likely oil-impacted) areas of Terrebonne and Barataria Bay have shown, via satellite data, a distinct decline in marsh vegetation coverage since 2010. Oysters appear to be affected by predation and salinity variation. Microbial diversity from marsh-edge sediments is distinct from before and after the spill, and between unoiled and oiled marshes, with lower diversity in oiled marshes; but the greatest community composition shifts are in marshes affected by the freshwater diversions. Changes in microbial diversity in the water column at the stream-side edge of oiled marshes are extensive and are related to marsh edge erosion. In contrast, oiling of marshes had no impact on ammonia oxidizer or denitrifier abundances and on soil biogeochemical process rates 2+ years post-spill. Analysis of long-term offshore phytoplankton community and hypoxia data indicate some signal of the Macondo oil, but these components of the ecosystem remain mostly influenced by the fresh water and nutrients delivered by the Mississippi River. The consortium continues to work to tease apart oil impacts, effects of salinity, natural variation, and disturbance from tropical storms and hurricanes to determine the trajectory for health of shelf waters and Louisiana's marshes.