223
of Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA)
(Quigg et al. 2020; Passow et al. 2012; Ziervogel et al. 2012; Passow 2014; Brooks
et al. 2015; Romero et al. 2015; Daly et al. 2016; Schwing et al. 2017a; Romero
et al. 2017). There are several regionally and temporally dependent factors that
affect the formation of MOSSFA including three primary components: (1) riverine
influences (nutrients, clay minerals, salinity), (2) marine biota (microbial, algal,
stress response formation of exopolymeric substances), and (3) petroleum (petrogenic and pyrogenic sources). Components 1 and 2 are exacerbated in deltaic systems with strong gradients and high organic carbon production and deposition rates
(Quigg et al. 2020).
The Ixtoc 1 subsurface marine petroleum blowout released 3 million barrels of
petroleum from 50 meters water depth into the southern GoM over the course of
290 days from 1979 to 1980 (Jernelov and Linden 1981). While in situ water column and seafloor measurements were spatially limited (primarily surrounding the
wellhead) at the time of the spill, all of the necessary contributing factors for
MOSSFA formation were present. Vonk et al. (2015) performed a meta-analysis of
all major accidental oil releases and found that MOSSFA likely occurred during
Ixtoc 1 based on the presence of microbial communities, algae, river-derived particulate matter (Gracia et al. 2013), and dispersant usage.
During and directly following DWH in 2010, a series of sediment cores was collected throughout the northern GoM to produce a multi-proxy record of MOSSFA
inputs, postdepositional processes, and seafloor spatial extent (Fig. 13.1). These
collections continued annually from 2010 to 2017. Sediment cores were also collected from 2015 to 2016 throughout the southern GoM in open marine and coastal
environments to assess the presence and long-term preservation of MOSSFA related
to Ixtoc 1. All cores were extruded at 2–5 mm scale (Schwing et al. 2016) to properly characterize both oil spill events at sufficient temporal resolution (sub-annual
to sub-decadal). This chapter introduces Part IV: Oil Spill Records in Deep Sea
Sediments and addresses a series of questions regarding MOSSFA in the sedimentary record:
• What were the characteristics of MOSSFA sedimentary inputs?
• What was the extent of MOSSFA on the seafloor?
• What postdepositional processes took place as a result of MOSSFA?
• Can MOSSFA be preserved in the sedimentary record?
13.2 What Were the Characteristics of MOSSFA
Sedimentary Inputs?
The initial evidence of MOSSFA on the seafloor in the northern GoM, following
DWH, was an increase in sediment accumulation rates. Brooks et al. (2015) found
that mass accumulation rates increased by four- to tenfold in the northern GoM
relative to pre-DWH accumulation rates using a novel short-lived radioisotope
application of excess
234
Th (
234
Th xs ). This approach can only be utilized in cases
13 The Sedimentary Record of MOSSFA Events in the Gulf of Mexico: A Comparison…
of Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA)
(Quigg et al. 2020; Passow et al. 2012; Ziervogel et al. 2012; Passow 2014; Brooks
et al. 2015; Romero et al. 2015; Daly et al. 2016; Schwing et al. 2017a; Romero
et al. 2017). There are several regionally and temporally dependent factors that
affect the formation of MOSSFA including three primary components: (1) riverine
influences (nutrients, clay minerals, salinity), (2) marine biota (microbial, algal,
stress response formation of exopolymeric substances), and (3) petroleum (petrogenic and pyrogenic sources). Components 1 and 2 are exacerbated in deltaic systems with strong gradients and high organic carbon production and deposition rates
(Quigg et al. 2020).
The Ixtoc 1 subsurface marine petroleum blowout released 3 million barrels of
petroleum from 50 meters water depth into the southern GoM over the course of
290 days from 1979 to 1980 (Jernelov and Linden 1981). While in situ water column and seafloor measurements were spatially limited (primarily surrounding the
wellhead) at the time of the spill, all of the necessary contributing factors for
MOSSFA formation were present. Vonk et al. (2015) performed a meta-analysis of
all major accidental oil releases and found that MOSSFA likely occurred during
Ixtoc 1 based on the presence of microbial communities, algae, river-derived particulate matter (Gracia et al. 2013), and dispersant usage.
During and directly following DWH in 2010, a series of sediment cores was collected throughout the northern GoM to produce a multi-proxy record of MOSSFA
inputs, postdepositional processes, and seafloor spatial extent (Fig. 13.1). These
collections continued annually from 2010 to 2017. Sediment cores were also collected from 2015 to 2016 throughout the southern GoM in open marine and coastal
environments to assess the presence and long-term preservation of MOSSFA related
to Ixtoc 1. All cores were extruded at 2–5 mm scale (Schwing et al. 2016) to properly characterize both oil spill events at sufficient temporal resolution (sub-annual
to sub-decadal). This chapter introduces Part IV: Oil Spill Records in Deep Sea
Sediments and addresses a series of questions regarding MOSSFA in the sedimentary record:
• What were the characteristics of MOSSFA sedimentary inputs?
• What was the extent of MOSSFA on the seafloor?
• What postdepositional processes took place as a result of MOSSFA?
• Can MOSSFA be preserved in the sedimentary record?
13.2 What Were the Characteristics of MOSSFA
Sedimentary Inputs?
The initial evidence of MOSSFA on the seafloor in the northern GoM, following
DWH, was an increase in sediment accumulation rates. Brooks et al. (2015) found
that mass accumulation rates increased by four- to tenfold in the northern GoM
relative to pre-DWH accumulation rates using a novel short-lived radioisotope
application of excess
234
Th (
234
Th xs ). This approach can only be utilized in cases
13 The Sedimentary Record of MOSSFA Events in the Gulf of Mexico: A Comparison…