174
spheric pressure (0.1 MPa) (Schedler et al. 2014). Rhodococcus PC20, isolated
from the deep- sea sediment of the Gulf of Mexico (GoM), has comparable growth
at 15 MPa and atmospheric pressure. However, in the presence of dispersant
COREXIT 9500A, the growth further diminishes, suggesting an enhanced toxicity
of the dispersant at elevated pressure (Hackbusch et al. submitted). On the other
hand, growth of aromatic hydrocarbon-degrading Sphingobium yanoikuyae B1 is
strongly impacted by pressure as low as 8.8 MPa (Schedler et al. 2014). Pressure
also exhibits an inhibitory effect on hydrocarbon-degrading indigenous microbial
community under nutrient- replete conditions, with a 4% decrease in n-alkane degradation for every 1 MPa increase (Nguyen et al. 2018). Application of high-pressure hydrocarbon degradation rates into a model increases accuracy of predictions
with time, suggesting that high-pressure biodegradation is one of the mechanisms
for the persistence of deepwater plume (Lindo-Atichati et al. 2014).
11.2.3 Sediment Analysis
A large-scale spatial model of the deposition of petroleum hydrocarbons following
the DWH spill was generated to provide a better guidance for future accidental
releases of oil contaminants from deep waters (Romero et al. 2017). In that study,
sediment cores (n = 2613) were collected and chemically analyzed by different
institutions (University of South Florida, US Government, and BP P.L.C.) from
coastal to deep-sea areas in the GoM (total area coverage: 194000 km
2
). A wide
range of compounds were included in the spatial analysis to include the different
hydrocarbon mixtures produced during the DWH spill due to partitioning of the oil
within the water column (subsurface intrusion layers, oil slick, oil-mineral aggregates). In addition, due to multiple hydrocarbon sources in the GoM, hydrocarbon
concentrations were compared within sediment core layers to distinguish background in each site to post-spill levels.
Results indicate that ~9.1 ± 4.1 × 10
4
metric tons of DWH oil was deposited in
~110,000 km
2
, containing 21% on average (up to 47%) of the total amount of oil
discharged and not recovered from the DWH spill, similar to the unaccounted
amount of oil reported previously (McNutt et al. 2012a). Relative to the oil mass
that remained in the environment, a large deposit of oil occurred in coastal (up to
43% in ~34,000 km
2
) and deep-sea (up to 4% in ~33,000 km
2
) areas, while negligible deposition was observed on the continental shelf (up to 0.5% in ~43,000 km
2
,
behaving as a transition zone in the northern GoM). Spatial trends in the amount and
composition of deposited hydrocarbons in sediments demonstrated that weathering
occurred mostly before deposition of DWH oil via various natural processes (evaporation, dissolution, degradation, photooxidation) and anthropogenic (burning of surface slick), depending on the area of deposition.
Schwing et al. (2017) employed a commonly used radioisotope tracer (excess
210
Pb or
210
Pb xs ) in sediment cores to characterize the spatial extent in the deepsea area of the large sedimentation event occurred after the DWH spill (Brooks
N. Perlin et al.
spheric pressure (0.1 MPa) (Schedler et al. 2014). Rhodococcus PC20, isolated
from the deep- sea sediment of the Gulf of Mexico (GoM), has comparable growth
at 15 MPa and atmospheric pressure. However, in the presence of dispersant
COREXIT 9500A, the growth further diminishes, suggesting an enhanced toxicity
of the dispersant at elevated pressure (Hackbusch et al. submitted). On the other
hand, growth of aromatic hydrocarbon-degrading Sphingobium yanoikuyae B1 is
strongly impacted by pressure as low as 8.8 MPa (Schedler et al. 2014). Pressure
also exhibits an inhibitory effect on hydrocarbon-degrading indigenous microbial
community under nutrient- replete conditions, with a 4% decrease in n-alkane degradation for every 1 MPa increase (Nguyen et al. 2018). Application of high-pressure hydrocarbon degradation rates into a model increases accuracy of predictions
with time, suggesting that high-pressure biodegradation is one of the mechanisms
for the persistence of deepwater plume (Lindo-Atichati et al. 2014).
11.2.3 Sediment Analysis
A large-scale spatial model of the deposition of petroleum hydrocarbons following
the DWH spill was generated to provide a better guidance for future accidental
releases of oil contaminants from deep waters (Romero et al. 2017). In that study,
sediment cores (n = 2613) were collected and chemically analyzed by different
institutions (University of South Florida, US Government, and BP P.L.C.) from
coastal to deep-sea areas in the GoM (total area coverage: 194000 km
2
). A wide
range of compounds were included in the spatial analysis to include the different
hydrocarbon mixtures produced during the DWH spill due to partitioning of the oil
within the water column (subsurface intrusion layers, oil slick, oil-mineral aggregates). In addition, due to multiple hydrocarbon sources in the GoM, hydrocarbon
concentrations were compared within sediment core layers to distinguish background in each site to post-spill levels.
Results indicate that ~9.1 ± 4.1 × 10
4
metric tons of DWH oil was deposited in
~110,000 km
2
, containing 21% on average (up to 47%) of the total amount of oil
discharged and not recovered from the DWH spill, similar to the unaccounted
amount of oil reported previously (McNutt et al. 2012a). Relative to the oil mass
that remained in the environment, a large deposit of oil occurred in coastal (up to
43% in ~34,000 km
2
) and deep-sea (up to 4% in ~33,000 km
2
) areas, while negligible deposition was observed on the continental shelf (up to 0.5% in ~43,000 km
2
,
behaving as a transition zone in the northern GoM). Spatial trends in the amount and
composition of deposited hydrocarbons in sediments demonstrated that weathering
occurred mostly before deposition of DWH oil via various natural processes (evaporation, dissolution, degradation, photooxidation) and anthropogenic (burning of surface slick), depending on the area of deposition.
Schwing et al. (2017) employed a commonly used radioisotope tracer (excess
210
Pb or
210
Pb xs ) in sediment cores to characterize the spatial extent in the deepsea area of the large sedimentation event occurred after the DWH spill (Brooks
N. Perlin et al.