206
underestimates of the oil that sank, except if the core was collected in a low point on
the seafloor (more below). The delivery of oil chemicals to the benthos and surface
sediments is important to the fate of oil in marine ecosystems and its effects on
benthic organisms or those that feed on benthic organisms.
MOSSFA (Marine Oil Snow Sedimentation and Flocculent Accumulation) is a
term coined in October 2013 (see Daly et al. 2016) to evaluate the processes influencing the formation and fate of oil-associated marine snow as summarized in
Fig. 12.2. Participants on oil spill response cruises in May and June of 2010 observed
elevated marine snow particles both at the sea surface and throughout the water
column (Passow et al. 2012; Passow 2016; Daly et al. 2016). Sedimentation of MOS
to the seafloor was later documented by sediment traps (Yan et al. 2016) and sediment cores (Montagna et al. 2013; Valentine et al. 2014; Brooks et al. 2015; Romero
et al. 2015). The mass deposition of MOS occurred over a 4–5-month period during
and after the oil spill and far exceeded pre-spill sediment accumulation rates (Brooks
et al. 2015). Deep-sea sediment traps revealed MOS “flocs” (Stout and German, 2015;
Yan et al. 2016) up to 8 km from the well (Stout and Payne 2016a, b). Valentine
et al. (2014) used hopanes as a biomarker tracer to estimate that 1.8–14% of the oil
was transported to the seafloor, while Chanton et al. (2015) estimated the amount to
be between 0.5% and 9% using radiocarbon distributions. A reevaluation of sedimentary geochemical data revealed that 21 ± 10% of the total amount of oil discharged, and not recovered from the DwH spill, sedimented to the seafloor (Romero
et al. 2017). Thus, the DwH MOSSFA event was a significant pathway for the
distribution and fate of spilled oil. Information on the processes impacting MOSSFA
are needed.
Owing to intense scientific interest in the impacts of MOS, the Gulf of Mexico
Research Initiative funded the first MOSSFA Workshop in October 2013, with the
goal to evaluate what was known on three topics: (1) factors affecting the formation
and sinking of MOS in the water column; (2) the deposition, accumulation, and
biogeochemical fate of MOS on the seafloor; and (3) the ecologic impacts of MOS
on pelagic and benthic species and communities. The results of the MOSSFA
Workshop are reported in Daly et al. (2016), as well as a summary of published
results at that time. There are many factors that are thought to affect the formation
and alteration of MOS aggregates in the water column (Fig. 12.2). One major surface process relevant during the DwH was the elevated and extended Mississippi
River discharge, which enhanced phytoplankton production and suspended particle
concentrations, zooplankton grazing, and enhanced microbial mucus formation.
Freshwater diversions along the lower Mississippi River were opened for several
months in order to reduce the impact of the oil spill on estuaries and wetlands
(Bianchi et al. 2011). As a result, a low salinity lens of river water created a shallow
mixed layer, which extended over a large area to the east of the DwH wellhead
(O’Connor et al. 2016). Due to the river water and possibly the presence of oil,
unusually large phytoplankton blooms occurred in the region. Specifically, the elevated phytoplankton concentrations were detected by satellite as a >1 mg m
−3
chlorophyll a anomaly to the east of the wellhead, covering more than 11,000 km
2
A. Quigg et al.
underestimates of the oil that sank, except if the core was collected in a low point on
the seafloor (more below). The delivery of oil chemicals to the benthos and surface
sediments is important to the fate of oil in marine ecosystems and its effects on
benthic organisms or those that feed on benthic organisms.
MOSSFA (Marine Oil Snow Sedimentation and Flocculent Accumulation) is a
term coined in October 2013 (see Daly et al. 2016) to evaluate the processes influencing the formation and fate of oil-associated marine snow as summarized in
Fig. 12.2. Participants on oil spill response cruises in May and June of 2010 observed
elevated marine snow particles both at the sea surface and throughout the water
column (Passow et al. 2012; Passow 2016; Daly et al. 2016). Sedimentation of MOS
to the seafloor was later documented by sediment traps (Yan et al. 2016) and sediment cores (Montagna et al. 2013; Valentine et al. 2014; Brooks et al. 2015; Romero
et al. 2015). The mass deposition of MOS occurred over a 4–5-month period during
and after the oil spill and far exceeded pre-spill sediment accumulation rates (Brooks
et al. 2015). Deep-sea sediment traps revealed MOS “flocs” (Stout and German, 2015;
Yan et al. 2016) up to 8 km from the well (Stout and Payne 2016a, b). Valentine
et al. (2014) used hopanes as a biomarker tracer to estimate that 1.8–14% of the oil
was transported to the seafloor, while Chanton et al. (2015) estimated the amount to
be between 0.5% and 9% using radiocarbon distributions. A reevaluation of sedimentary geochemical data revealed that 21 ± 10% of the total amount of oil discharged, and not recovered from the DwH spill, sedimented to the seafloor (Romero
et al. 2017). Thus, the DwH MOSSFA event was a significant pathway for the
distribution and fate of spilled oil. Information on the processes impacting MOSSFA
are needed.
Owing to intense scientific interest in the impacts of MOS, the Gulf of Mexico
Research Initiative funded the first MOSSFA Workshop in October 2013, with the
goal to evaluate what was known on three topics: (1) factors affecting the formation
and sinking of MOS in the water column; (2) the deposition, accumulation, and
biogeochemical fate of MOS on the seafloor; and (3) the ecologic impacts of MOS
on pelagic and benthic species and communities. The results of the MOSSFA
Workshop are reported in Daly et al. (2016), as well as a summary of published
results at that time. There are many factors that are thought to affect the formation
and alteration of MOS aggregates in the water column (Fig. 12.2). One major surface process relevant during the DwH was the elevated and extended Mississippi
River discharge, which enhanced phytoplankton production and suspended particle
concentrations, zooplankton grazing, and enhanced microbial mucus formation.
Freshwater diversions along the lower Mississippi River were opened for several
months in order to reduce the impact of the oil spill on estuaries and wetlands
(Bianchi et al. 2011). As a result, a low salinity lens of river water created a shallow
mixed layer, which extended over a large area to the east of the DwH wellhead
(O’Connor et al. 2016). Due to the river water and possibly the presence of oil,
unusually large phytoplankton blooms occurred in the region. Specifically, the elevated phytoplankton concentrations were detected by satellite as a >1 mg m
−3
chlorophyll a anomaly to the east of the wellhead, covering more than 11,000 km
2
A. Quigg et al.