238
A primary depositional mechanism for oiled sedimentation was the observed
Marine Oil Snow Sedimentation and Flocculent accumulation (MOSSFA), which
consisted of surface oil interacting with biology, primarily phytoplankton (Quigg
et al. 2020; Daly et al. 2016; Passow et al. 2016; Ziervogel et al. 2012; Passow et al.
2012). The interaction of this sticky substance combined with oil, dispersants, and
clay particles in the water column leads to aggregation of marine oil snow, which
lost buoyancy and rapidly settled through the water column, stripping particles and
transporting them to the seafloor as MOSSFA (Passow et al. 2012; Brooks et al.
2015).
The DWH blowout event was of short duration (geologically), on the scale of
months. Understanding the manifestation of this event in the sedimentary system
and impacts to the benthos required rapid response and adaptive approaches.
Studying the sedimentary system before, during, and after an oil spill event, such as
the DWH blowout, allows for the assessment of benthic sedimentological, biological, and ecological implications ranging from acute/short-term to long-term/permanent impacts. The short- and long-term fate of oil-contaminated sediments can be
described in terms of (1) the initial distribution patterns providing insight into the
depositional mechanism(s) and source(s) of sedimented oil, such as MOSSFA, (2)
the potential redistribution of oil-contaminated sediments and secondary deposition
in benthic environments that may not have been initially impacted, and (3) the ultimate fate and potential for burial and sequestration of oil-contaminated sediments
in deep-sea sediments and by the benthos.
14.2 Approach/Methods
A total of 179 sediment cores collected between 2010 and 2016 at 80 sites to investigate the sedimentary impacts of the DWH blowout (Fig. 14.1b). Due to the “realtime” nature of the sediment investigations immediately following the DWH event,
it was expected that impacted sediments would be at the surface of the seafloor and
core collection with an intact sediment water interface was of critical importance.
Therefore, cores were collected using an Ocean Instruments MC-800 multicorer as
it delicately collects sediment cores up to ~60 cm in length while preserving the
sediment water interface, which is generally sufficient for capturing sedimentation
over the past ~100 years to adequately assess baseline sedimentation patterns. Also,
the MC-800 collects 8 cores simultaneously allowing for interdisciplinary studies
(sedimentology, biology, chemistry, etc.) to fully characterize the benthic response
and evolution during and following the event.
R. A. Larson et al.
A primary depositional mechanism for oiled sedimentation was the observed
Marine Oil Snow Sedimentation and Flocculent accumulation (MOSSFA), which
consisted of surface oil interacting with biology, primarily phytoplankton (Quigg
et al. 2020; Daly et al. 2016; Passow et al. 2016; Ziervogel et al. 2012; Passow et al.
2012). The interaction of this sticky substance combined with oil, dispersants, and
clay particles in the water column leads to aggregation of marine oil snow, which
lost buoyancy and rapidly settled through the water column, stripping particles and
transporting them to the seafloor as MOSSFA (Passow et al. 2012; Brooks et al.
2015).
The DWH blowout event was of short duration (geologically), on the scale of
months. Understanding the manifestation of this event in the sedimentary system
and impacts to the benthos required rapid response and adaptive approaches.
Studying the sedimentary system before, during, and after an oil spill event, such as
the DWH blowout, allows for the assessment of benthic sedimentological, biological, and ecological implications ranging from acute/short-term to long-term/permanent impacts. The short- and long-term fate of oil-contaminated sediments can be
described in terms of (1) the initial distribution patterns providing insight into the
depositional mechanism(s) and source(s) of sedimented oil, such as MOSSFA, (2)
the potential redistribution of oil-contaminated sediments and secondary deposition
in benthic environments that may not have been initially impacted, and (3) the ultimate fate and potential for burial and sequestration of oil-contaminated sediments
in deep-sea sediments and by the benthos.
14.2 Approach/Methods
A total of 179 sediment cores collected between 2010 and 2016 at 80 sites to investigate the sedimentary impacts of the DWH blowout (Fig. 14.1b). Due to the “realtime” nature of the sediment investigations immediately following the DWH event,
it was expected that impacted sediments would be at the surface of the seafloor and
core collection with an intact sediment water interface was of critical importance.
Therefore, cores were collected using an Ocean Instruments MC-800 multicorer as
it delicately collects sediment cores up to ~60 cm in length while preserving the
sediment water interface, which is generally sufficient for capturing sedimentation
over the past ~100 years to adequately assess baseline sedimentation patterns. Also,
the MC-800 collects 8 cores simultaneously allowing for interdisciplinary studies
(sedimentology, biology, chemistry, etc.) to fully characterize the benthic response
and evolution during and following the event.
R. A. Larson et al.