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PHC biodegradation in marine environments, relatively few studies have been
conducted under conditions resembling the deep sea. In particular, hydrostatic pressure is a key environmental parameter that has been largely overlooked in biodegradation studies, due to methodological challenges and the difficulty to obtain samples.
Considering the rapid expansion of oil and gas drilling into deeper waters, there is
an urgent need to improve understanding of the influence of low temperature and
high pressure on biodegradation in order to better constrain the fate of hydrocarbons
in the deep sea. This chapter addresses the current understanding of deep sea PHC
biodegradation, highlighting discoveries made during the scientific response to the
DWH disaster.
Keywords Biodegradation · Deep sea · Pressure · Temperature · Petroleum
hydrocarbon · Hydrocarbon-degrading bacteria
7.1 Introduction
Similar to the breakdown of natural organic matter, biodegradation mediated by
indigenous microbial communities is the ultimate fate of the majority of petroleum
hydrocarbons (oil and gas) that enter the marine environment (Leahy and Colwell
1990; Hazen and Prince 2015; Joye et al. 2016). The fate and transport of discharged
oil are in turn determined by a complex interplay between hydrocarbon chemistry,
the microbial food web, and ambient oceanographic processes including dispersion,
dilution, dissolution, advection by ocean currents, particle flocculation and aggregation, sedimentation, and evaporation, along with biodegradation (Fig. 7.1). A suite
of environmental parameters limits the capacity and efficiency of microbial communities to degrade petroleum hydrocarbons in marine ecosystems. All of the same
environmental pressures that impact microbial food webs are in play during oil
discharge including temperature, pressure, oxygen and nutrient availability, and
physical or chemical form of the oil (Head et al. 2006).
Defined as the region below 200 m of water depth, the deep sea is cold, dark, and
exposed to incredibly high hydrostatic pressures. Although it comprises the largest
habitat for life on the planet and covers the majority of Earth’s surface area, the lack
of light precludes photosynthetic production, and biological communities are
dependent upon sedimented organic matter originating from the surface ocean.
Further, temperatures at the seafloor approach 3–4 °C, and hydrostatic pressure
increases with depth (1.0 MPa per 100 m) (Jørgensen and Boetius 2007). Thus, in
general, the deep ocean can be considered as a biological desert as well as an
extreme environment for life.
The Deepwater Horizon (DWH) disaster represents the largest accidental
marine oil spill in history. One of the unique characteristics of the DWH spill is the
depth at which it occurred, approximately one mile below the sea surface. Spanning
3 months, approximately 4.1–4.9 million barrels of crude oil were discharged into
J. E. Kostka et al.
PHC biodegradation in marine environments, relatively few studies have been
conducted under conditions resembling the deep sea. In particular, hydrostatic pressure is a key environmental parameter that has been largely overlooked in biodegradation studies, due to methodological challenges and the difficulty to obtain samples.
Considering the rapid expansion of oil and gas drilling into deeper waters, there is
an urgent need to improve understanding of the influence of low temperature and
high pressure on biodegradation in order to better constrain the fate of hydrocarbons
in the deep sea. This chapter addresses the current understanding of deep sea PHC
biodegradation, highlighting discoveries made during the scientific response to the
DWH disaster.
Keywords Biodegradation · Deep sea · Pressure · Temperature · Petroleum
hydrocarbon · Hydrocarbon-degrading bacteria
7.1 Introduction
Similar to the breakdown of natural organic matter, biodegradation mediated by
indigenous microbial communities is the ultimate fate of the majority of petroleum
hydrocarbons (oil and gas) that enter the marine environment (Leahy and Colwell
1990; Hazen and Prince 2015; Joye et al. 2016). The fate and transport of discharged
oil are in turn determined by a complex interplay between hydrocarbon chemistry,
the microbial food web, and ambient oceanographic processes including dispersion,
dilution, dissolution, advection by ocean currents, particle flocculation and aggregation, sedimentation, and evaporation, along with biodegradation (Fig. 7.1). A suite
of environmental parameters limits the capacity and efficiency of microbial communities to degrade petroleum hydrocarbons in marine ecosystems. All of the same
environmental pressures that impact microbial food webs are in play during oil
discharge including temperature, pressure, oxygen and nutrient availability, and
physical or chemical form of the oil (Head et al. 2006).
Defined as the region below 200 m of water depth, the deep sea is cold, dark, and
exposed to incredibly high hydrostatic pressures. Although it comprises the largest
habitat for life on the planet and covers the majority of Earth’s surface area, the lack
of light precludes photosynthetic production, and biological communities are
dependent upon sedimented organic matter originating from the surface ocean.
Further, temperatures at the seafloor approach 3–4 °C, and hydrostatic pressure
increases with depth (1.0 MPa per 100 m) (Jørgensen and Boetius 2007). Thus, in
general, the deep ocean can be considered as a biological desert as well as an
extreme environment for life.
The Deepwater Horizon (DWH) disaster represents the largest accidental
marine oil spill in history. One of the unique characteristics of the DWH spill is the
depth at which it occurred, approximately one mile below the sea surface. Spanning
3 months, approximately 4.1–4.9 million barrels of crude oil were discharged into
J. E. Kostka et al.