269
© Springer Nature Switzerland AG 2020
S. A. Murawski et al. (eds.), Deep Oil Spills,
https://doi.org/10.1007/978-3-030-11605-7_16
Chapter 16
Changes in Redox Conditions of Surface
Sediments Following the Deepwater
Horizon and Ixtoc 1 Events
David W. Hastings, Thea Bartlett, Gregg R. Brooks, Rebekka A. Larson,
Kelly A. Quinn, Daniel Razionale, Patrick T. Schwing,
Libia Hascibe Pérez Bernal, Ana Carolina Ruiz-Fernández,
Joan- Albert Sánchez-Cabeza, and David J. Hollander
Abstract Following the blowout of the Macondo well, a sedimentation pulse
resulted in significant changes in sedimentary redox conditions. This is demonstrated by downcore and temporal changes in the concentration of redox-sensitive
metals: Mn and Re. Sediment cores collected in the NE Gulf of Mexico reveal
increased sedimentation after the Deepwater Horizon (DWH) blowout. The formation of mucous-rich marine snow in surface waters and subsequent rapid deposition
to sediments is the likely cause. Respiration of this material resulted in decreased
pore-water oxygen and a shoaled redoxcline, resulting in two distinct Mn peaks in
sediments following the event, one typically in the top 5–7 mm, with the other at
20–30 mm. Cores near the wellhead reveal this nonsteady-state behavior for
3–5 years after the event. A time series reveals that bulk sediment Re increased 3–4
times compared to the pre-impact baseline value for 2–3 years indicating sediments
are increasingly more reducing. Three years after the blowout, subsurface Re
reaches a plateau suggesting a return to steady-state conditions. In select sites where
D. W. Hastings (*) · G. R. Brooks · D. Razionale
Eckerd College, St. Petersburg, FL, USA
e-mail: hastindw@eckerd.edu; brooksgr@eckerd.edu; dprazion@eckerd.edu
T. Bartlett · K. A. Quinn · P. T. Schwing · D. J. Hollander
College of Marine Science, University of South Florida, St. Petersburg, FL, USA
e-mail: theabartlett@mail.usf.edu; kaquinn2@usf.edu; pschwing@mail.usf.edu;
davidh@usf.edu
R. A. Larson
Eckerd College, St. Petersburg, FL, USA
College of Marine Science, University of South Florida, St. Petersburg, FL, USA
e-mail: larsonra@eckerd.edu
L. H. P. Bernal · A. C. Ruiz-Fernández · J.-A. Sánchez-Cabeza
Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México,
Mexico City, Mexico
e-mail: lbernal@ola.icmyl.unam.mx; caro@ola.icmyl.unam.mx; jasanchez@cmarl.unam.mx
© Springer Nature Switzerland AG 2020
S. A. Murawski et al. (eds.), Deep Oil Spills,
https://doi.org/10.1007/978-3-030-11605-7_16
Chapter 16
Changes in Redox Conditions of Surface
Sediments Following the Deepwater
Horizon and Ixtoc 1 Events
David W. Hastings, Thea Bartlett, Gregg R. Brooks, Rebekka A. Larson,
Kelly A. Quinn, Daniel Razionale, Patrick T. Schwing,
Libia Hascibe Pérez Bernal, Ana Carolina Ruiz-Fernández,
Joan- Albert Sánchez-Cabeza, and David J. Hollander
Abstract Following the blowout of the Macondo well, a sedimentation pulse
resulted in significant changes in sedimentary redox conditions. This is demonstrated by downcore and temporal changes in the concentration of redox-sensitive
metals: Mn and Re. Sediment cores collected in the NE Gulf of Mexico reveal
increased sedimentation after the Deepwater Horizon (DWH) blowout. The formation of mucous-rich marine snow in surface waters and subsequent rapid deposition
to sediments is the likely cause. Respiration of this material resulted in decreased
pore-water oxygen and a shoaled redoxcline, resulting in two distinct Mn peaks in
sediments following the event, one typically in the top 5–7 mm, with the other at
20–30 mm. Cores near the wellhead reveal this nonsteady-state behavior for
3–5 years after the event. A time series reveals that bulk sediment Re increased 3–4
times compared to the pre-impact baseline value for 2–3 years indicating sediments
are increasingly more reducing. Three years after the blowout, subsurface Re
reaches a plateau suggesting a return to steady-state conditions. In select sites where
D. W. Hastings (*) · G. R. Brooks · D. Razionale
Eckerd College, St. Petersburg, FL, USA
e-mail: hastindw@eckerd.edu; brooksgr@eckerd.edu; dprazion@eckerd.edu
T. Bartlett · K. A. Quinn · P. T. Schwing · D. J. Hollander
College of Marine Science, University of South Florida, St. Petersburg, FL, USA
e-mail: theabartlett@mail.usf.edu; kaquinn2@usf.edu; pschwing@mail.usf.edu;
davidh@usf.edu
R. A. Larson
Eckerd College, St. Petersburg, FL, USA
College of Marine Science, University of South Florida, St. Petersburg, FL, USA
e-mail: larsonra@eckerd.edu
L. H. P. Bernal · A. C. Ruiz-Fernández · J.-A. Sánchez-Cabeza
Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México,
Mexico City, Mexico
e-mail: lbernal@ola.icmyl.unam.mx; caro@ola.icmyl.unam.mx; jasanchez@cmarl.unam.mx