Sedimentation Pulse in the NE Gulf of Mexico following the 2010 DWH Blowout

PLoS One. 2015 Jul 14;10(7):e0132341. doi: 10.1371/journal.pone.0132341. eCollection 2015.

Abstract

The objective of this study was to investigate the impacts of the Deepwater Horizon (DWH) oil discharge at the seafloor as recorded in bottom sediments of the DeSoto Canyon region in the northeastern Gulf of Mexico. Through a close coupling of sedimentological, geochemical, and biological approaches, multiple independent lines of evidence from 11 sites sampled in November/December 2010 revealed that the upper ~1 cm depth interval is distinct from underlying sediments and results indicate that particles originated at the sea surface. Consistent dissimilarities in grain size over the surficial ~1 cm of sediments correspond to excess (234)Th depths, which indicates a lack of vertical mixing (bioturbation), suggesting the entire layer was deposited within a 4-5 month period. Further, a time series from four deep-sea sites sampled up to three additional times over the following two years revealed that excess (234)Th depths, accumulation rates, and (234)Th inventories decreased rapidly, within a few to several months after initial coring. The interpretation of a rapid sedimentation pulse is corroborated by stratification in solid phase Mn, which is linked to diagenesis and redox change, and the dramatic decrease in benthic formanifera density that was recorded in surficial sediments. Results are consistent with a brief depositional pulse that was also reported in previous studies of sediments, and marine snow formation in surface waters closer to the wellhead during the summer and fall of 2010. Although sediment input from the Mississippi River and advective transport may influence sedimentation on the seafloor in the DeSoto Canyon region, we conclude based on multidisciplinary evidence that the sedimentation pulse in late 2010 is the product of marine snow formation and is likely linked to the DWH discharge.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Foraminifera
  • Geologic Sediments / chemistry*
  • Geologic Sediments / microbiology*
  • Gulf of Mexico
  • Half-Life
  • Petroleum Pollution / adverse effects*
  • Radioisotopes / analysis
  • Radioisotopes / chemistry

Substances

  • Radioisotopes

Grants and funding

Funding was provided by the Gulf of Mexico Research Initiative (http://gulfresearchinitiative.org) through the Florida Institute of Oceanography (http://www.fio.usf.edu), Center for Integrated Modeling and Analysis of Gulf Ecosystems (http://www.marine.usf.edu/c-image/), and Deepsea to Coast Connectivity in the Eastern Gulf of Mexico (http://deep-c.org) consortia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Environchron provided support in the form of salaries for authors C.W.H., but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.