270
benthic foraminifera were counted, an assemblage-wide decrease is coincident with
reducing conditions, demonstrating the important consequences of changing redox
conditions on benthic ecosystems.
Another major submarine blowout in the southern Gulf of Mexico (Ixtoc 1;
1979–1980) released a large volume of crude oil below the surface. We observe
multiple Mn oxide peaks associated with a shoaling redoxcline and Re maxima
associated with more reducing conditions. Nonsteady-state behavior at sites near
DWH and Ixtoc 1 is consistent with a MOSSFA (marine oil snow sedimentation and
flocculent accumulation) event at both locations.
Keywords Oil spill · Gulf of Mexico · Deepwater Horizon · Redox · Trace metal ·
Rhenium · Manganese
16.1 Introduction
The oil spill associated with the 2010 blowout of the Macondo Well at the Deepwater
Horizon oil rig released more oil than any other marine oil spill in history from an
ultra-deep well at 1500 m. The exact amount is somewhat controversial; Joye et al.
(2011) estimated the amount released was between 4.5 and 6.3 million barrels,
while the US District Court (2015) set the amount at four million barrels released,
which is considered a legal compromise. More dispersant was used in cleanup operations than ever before (about 2.1 million gallons). Jack Davis referred to it as “the
worst oil spill in history” in his recent Pulitzer Prize winning book on the history of
the Gulf of Mexico (Davis 2017).
Another remarkable aspect was the unexpected sedimentation event during and
after the blowout. A massive pulse in sedimentation over an extensive area in the NE
Gulf of Mexico (NGoM) occurred over a 4- to 5-month period during and after the
oil spill (Daly et al. 2016; Passow 2016). This mass deposition was likely due to the
formation of mucous-rich marine snow in surface waters and subsequent rapid
deposition to marine sediments (Daly et al. 2016; Passow 2016). Mass accumulation rates following the event were far greater than before the spill (Brooks et al.
2015; Larson et al. 2020). In spite of its lower density, oil from the spill was transported to the seafloor via rapidly sinking, oil-mineral aggregates. This oil-associated
marine snow became a focus of attention and resulted in the description of a new
phenomenon termed marine oil snow sedimentation and flocculent accumulation
(MOSSFA), fully explained in Chaps. 12 (Quigg et al. 2020) and 13 (Schwing et al.
2020).
The spatial extent of MOSSFA in the deep Gulf of Mexico was on the order of
35,000 km
2
(Romero et al. 2017). Several mechanisms have been proposed to
explain the formation of the MOSSFA event, including coagulation of phytoplankton and/or suspended matter with the oil droplets; and production of mucosoid
material from the degraders of the oil, which grew and multiplied rapidly following
the event (Passow et al. 2012). The microbial production of sticky transparent
exopolymeric particles (TEP) enhances the aggregation process, as would the
D. W. Hastings et al.
benthic foraminifera were counted, an assemblage-wide decrease is coincident with
reducing conditions, demonstrating the important consequences of changing redox
conditions on benthic ecosystems.
Another major submarine blowout in the southern Gulf of Mexico (Ixtoc 1;
1979–1980) released a large volume of crude oil below the surface. We observe
multiple Mn oxide peaks associated with a shoaling redoxcline and Re maxima
associated with more reducing conditions. Nonsteady-state behavior at sites near
DWH and Ixtoc 1 is consistent with a MOSSFA (marine oil snow sedimentation and
flocculent accumulation) event at both locations.
Keywords Oil spill · Gulf of Mexico · Deepwater Horizon · Redox · Trace metal ·
Rhenium · Manganese
16.1 Introduction
The oil spill associated with the 2010 blowout of the Macondo Well at the Deepwater
Horizon oil rig released more oil than any other marine oil spill in history from an
ultra-deep well at 1500 m. The exact amount is somewhat controversial; Joye et al.
(2011) estimated the amount released was between 4.5 and 6.3 million barrels,
while the US District Court (2015) set the amount at four million barrels released,
which is considered a legal compromise. More dispersant was used in cleanup operations than ever before (about 2.1 million gallons). Jack Davis referred to it as “the
worst oil spill in history” in his recent Pulitzer Prize winning book on the history of
the Gulf of Mexico (Davis 2017).
Another remarkable aspect was the unexpected sedimentation event during and
after the blowout. A massive pulse in sedimentation over an extensive area in the NE
Gulf of Mexico (NGoM) occurred over a 4- to 5-month period during and after the
oil spill (Daly et al. 2016; Passow 2016). This mass deposition was likely due to the
formation of mucous-rich marine snow in surface waters and subsequent rapid
deposition to marine sediments (Daly et al. 2016; Passow 2016). Mass accumulation rates following the event were far greater than before the spill (Brooks et al.
2015; Larson et al. 2020). In spite of its lower density, oil from the spill was transported to the seafloor via rapidly sinking, oil-mineral aggregates. This oil-associated
marine snow became a focus of attention and resulted in the description of a new
phenomenon termed marine oil snow sedimentation and flocculent accumulation
(MOSSFA), fully explained in Chaps. 12 (Quigg et al. 2020) and 13 (Schwing et al.
2020).
The spatial extent of MOSSFA in the deep Gulf of Mexico was on the order of
35,000 km
2
(Romero et al. 2017). Several mechanisms have been proposed to
explain the formation of the MOSSFA event, including coagulation of phytoplankton and/or suspended matter with the oil droplets; and production of mucosoid
material from the degraders of the oil, which grew and multiplied rapidly following
the event (Passow et al. 2012). The microbial production of sticky transparent
exopolymeric particles (TEP) enhances the aggregation process, as would the
D. W. Hastings et al.