262
biomarkers in stratigraphic horizons corresponding to the DWH blowout can be
related to a hypothesized MOSFFA (Marine Oil Snow Sedimentation and Flocculent
Accumulation) event, which rapidly deposited large amount of mineral particles,
spilled MW oil, and microbial biomass to the seafloor (Daly et al. 2016).
More recently, Jaggi (2018) used FTICR-MS to analyze water-extractable
organic matter (WEOM) from the northern GoM (Gulf of Mexico) sediment, revealing a spectrum enriched with nitrogen-containing compounds, containing up to six
nitrogen heteroatoms, likely related to proteinaceous cell constituents. The sediment WEOM, when compared to the aquatic DOM, showed lower carbon number
and DBE values in the dominant species, likely representing the low molecular
weight intermediates from a series of hydrolytic, fermentative, and eventually respiratory processes taking place in the sediments. While the aquatic DOM creates
homogenous FTICR-MS spectra due to the slower transformations, dilutions, and
longer residence times of species in the water column, WEOM of recent sediments
shows a higher variability in the composition between different locations, owing to
the relatively faster deposition of fresh biomass. Thus, in general, the chemical
character of both water-extractable and lipid species in the sediments better reflects
the input signatures of different sources and likely acts as a better alternative for oil
spill assessments.
Noticeably, recent sediment analyses using ultrahigh-resolution mass spectrometry are still scarce. In this sense, nontargeted approaches, such as the RADAR
mode FTICR-MS approach previously explained, are potential tools to rapidly
expand the inventory of biomarkers and early diagenetic degradation products of
biological materials in recently deposited organic matter, where complex mechanisms are involved and multiproxy nontargeted approaches seem to be a better fit.
Such approaches show great promise for both pre-spill baseline characterization, as
well as for assessment of planktonic and benthic responses of microbial communities to petrogenic inputs.
15.5.1 FTICR-MS Characterization of Marine Oil Snow
Associations Generated by Oil Spills
In addition to previously known removal mechanisms for oil released into oceans,
one important discovery resulting from the DWH oil spill was the realization that
MOSSFA represents a significant fate for oil released into systems such as the Gulf
of Mexico (Daly et al. 2016; Quigg et al. 2016). MOSSFA is believed to occur when
sticky extracellular polymeric substances (EPS), excreted by microbial communities in response to oil presence, bring together oil, mineral, and biological materials
to form marine oil snow (MOS) particles that eventually settle out of the water
column and contribute to sedimentary material (Quigg et al. 2016). Studies conducted following the DWH spill suggest between 4% and 31% of oil released during
the spill may have been entrained in MOS and contributed to sediments (Chanton
et al. 2015; Valentine et al. 2014). FTICR-MS makes it possible to determine what
J. R. Radović et al.
biomarkers in stratigraphic horizons corresponding to the DWH blowout can be
related to a hypothesized MOSFFA (Marine Oil Snow Sedimentation and Flocculent
Accumulation) event, which rapidly deposited large amount of mineral particles,
spilled MW oil, and microbial biomass to the seafloor (Daly et al. 2016).
More recently, Jaggi (2018) used FTICR-MS to analyze water-extractable
organic matter (WEOM) from the northern GoM (Gulf of Mexico) sediment, revealing a spectrum enriched with nitrogen-containing compounds, containing up to six
nitrogen heteroatoms, likely related to proteinaceous cell constituents. The sediment WEOM, when compared to the aquatic DOM, showed lower carbon number
and DBE values in the dominant species, likely representing the low molecular
weight intermediates from a series of hydrolytic, fermentative, and eventually respiratory processes taking place in the sediments. While the aquatic DOM creates
homogenous FTICR-MS spectra due to the slower transformations, dilutions, and
longer residence times of species in the water column, WEOM of recent sediments
shows a higher variability in the composition between different locations, owing to
the relatively faster deposition of fresh biomass. Thus, in general, the chemical
character of both water-extractable and lipid species in the sediments better reflects
the input signatures of different sources and likely acts as a better alternative for oil
spill assessments.
Noticeably, recent sediment analyses using ultrahigh-resolution mass spectrometry are still scarce. In this sense, nontargeted approaches, such as the RADAR
mode FTICR-MS approach previously explained, are potential tools to rapidly
expand the inventory of biomarkers and early diagenetic degradation products of
biological materials in recently deposited organic matter, where complex mechanisms are involved and multiproxy nontargeted approaches seem to be a better fit.
Such approaches show great promise for both pre-spill baseline characterization, as
well as for assessment of planktonic and benthic responses of microbial communities to petrogenic inputs.
15.5.1 FTICR-MS Characterization of Marine Oil Snow
Associations Generated by Oil Spills
In addition to previously known removal mechanisms for oil released into oceans,
one important discovery resulting from the DWH oil spill was the realization that
MOSSFA represents a significant fate for oil released into systems such as the Gulf
of Mexico (Daly et al. 2016; Quigg et al. 2016). MOSSFA is believed to occur when
sticky extracellular polymeric substances (EPS), excreted by microbial communities in response to oil presence, bring together oil, mineral, and biological materials
to form marine oil snow (MOS) particles that eventually settle out of the water
column and contribute to sedimentary material (Quigg et al. 2016). Studies conducted following the DWH spill suggest between 4% and 31% of oil released during
the spill may have been entrained in MOS and contributed to sediments (Chanton
et al. 2015; Valentine et al. 2014). FTICR-MS makes it possible to determine what
J. R. Radović et al.