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21.1 Introduction
The deep ocean represents one of the few places left on the planet where humans are
still actively exploring and where innumerable insights have yet to be discovered. It
is therefore not surprising that the ecological impacts of oil spills on natural
resources of the deep ocean are only partially understood. Nevertheless, this chapter
aims to: describe some of the known adverse effects of releases of oil on deep ocean
resources, identify a broader range of potential spill-related impacts in deep-sea
habitats, and give examples of challenges that exist for scientists who attempt damage assessment work in the deep ocean. While there have been a number of accidents over the course of modern history where oil spills have occurred at depth,
none of these previous events were of the same scale as the 2010 Deepwater Horizon
oil spill. In light of the pace and trajectory of offshore oil and gas development, supported by recent federal policies aimed at further increasing the pace of offshore oil
and gas development (Federal Register 2017), it seems unlikely that the Deepwater
Horizon spill will be the last deep spill of its kind. We therefore draw heavily from
our experiences with the Deepwater Horizon oil spill in this chapter as we discuss
the impacts of deep oil spills on marine resources, with the caveat that, although
there are similarities in deep ocean habitats across the globe, and certain species
have widespread abundance, the information presented herein may not apply uniformly to all deep ocean habitats. We also highlight that we do not discuss herein the
impacts to surface and shoreline resources, as those impacts have been studied
extensively in the broader oil spill literature, but rather focus on the impacts of deep
oil spills to deep benthic resources.
One fortunate result of the Deepwater Horizon oil spill was the unprecedented
magnitude of scientific investigation that followed. Subsequent chapters in this
book will provide in detail specific results from this body of work. In order to set the
stage for these more detailed discussions, this chapter: (1) explains the regulatory
and legal context that directed tens of millions of dollars of deep-sea research and
ultimately led to the conclusions reached by the natural resource Trustees related to
the ecological impacts of the spill, (2) provides an overarching ecosystem-level perspective of impacts, and (3) shares some of the insights gained from overseeing and
guiding the government-funded investigative work to assess injuries to deep-sea
natural resources. This chapter draws from information presented originally in the
US Government’s Programmatic Damage Assessment and Restoration Plan, and
readers are encouraged to review that plan’s entirety for additional detail and context (Trustees 2016).
The ocean floor of the Gulf of Mexico is generally subdivided into three distinct
depth zones: the continental shelf (0–200 m); the continental slope (200–800 m),
which drops off more abruptly; and the deep benthos (below 800 m) (Fig. 21.1,
Trustees 2016). Characteristic biological resources inhabit each of these diverse zones,
due to differences in habitat (although some mobile resources move between them).
The vast majority of the seafloor along the Gulf of Mexico consists of muddy sediment substrate, though in certain areas hard substrates are present (Love et al. 2013).
21 Overview of Ecological Impacts of Deep Spills: Deepwater Horizon
21.1 Introduction
The deep ocean represents one of the few places left on the planet where humans are
still actively exploring and where innumerable insights have yet to be discovered. It
is therefore not surprising that the ecological impacts of oil spills on natural
resources of the deep ocean are only partially understood. Nevertheless, this chapter
aims to: describe some of the known adverse effects of releases of oil on deep ocean
resources, identify a broader range of potential spill-related impacts in deep-sea
habitats, and give examples of challenges that exist for scientists who attempt damage assessment work in the deep ocean. While there have been a number of accidents over the course of modern history where oil spills have occurred at depth,
none of these previous events were of the same scale as the 2010 Deepwater Horizon
oil spill. In light of the pace and trajectory of offshore oil and gas development, supported by recent federal policies aimed at further increasing the pace of offshore oil
and gas development (Federal Register 2017), it seems unlikely that the Deepwater
Horizon spill will be the last deep spill of its kind. We therefore draw heavily from
our experiences with the Deepwater Horizon oil spill in this chapter as we discuss
the impacts of deep oil spills on marine resources, with the caveat that, although
there are similarities in deep ocean habitats across the globe, and certain species
have widespread abundance, the information presented herein may not apply uniformly to all deep ocean habitats. We also highlight that we do not discuss herein the
impacts to surface and shoreline resources, as those impacts have been studied
extensively in the broader oil spill literature, but rather focus on the impacts of deep
oil spills to deep benthic resources.
One fortunate result of the Deepwater Horizon oil spill was the unprecedented
magnitude of scientific investigation that followed. Subsequent chapters in this
book will provide in detail specific results from this body of work. In order to set the
stage for these more detailed discussions, this chapter: (1) explains the regulatory
and legal context that directed tens of millions of dollars of deep-sea research and
ultimately led to the conclusions reached by the natural resource Trustees related to
the ecological impacts of the spill, (2) provides an overarching ecosystem-level perspective of impacts, and (3) shares some of the insights gained from overseeing and
guiding the government-funded investigative work to assess injuries to deep-sea
natural resources. This chapter draws from information presented originally in the
US Government’s Programmatic Damage Assessment and Restoration Plan, and
readers are encouraged to review that plan’s entirety for additional detail and context (Trustees 2016).
The ocean floor of the Gulf of Mexico is generally subdivided into three distinct
depth zones: the continental shelf (0–200 m); the continental slope (200–800 m),
which drops off more abruptly; and the deep benthos (below 800 m) (Fig. 21.1,
Trustees 2016). Characteristic biological resources inhabit each of these diverse zones,
due to differences in habitat (although some mobile resources move between them).
The vast majority of the seafloor along the Gulf of Mexico consists of muddy sediment substrate, though in certain areas hard substrates are present (Love et al. 2013).
21 Overview of Ecological Impacts of Deep Spills: Deepwater Horizon