Scenarios and Responses to Future Deep Oil Spills

Ultra-deep water production of oil and gas – from depths greater than 1 mile (1500 m) – comprises an ever-increasing proportion of the world’s supply of hydrocarbons. In the Gulf of Mexico, ultra-deep production now exceeds that from shallower waters. The ultra-deep domains of the world’s oceans are home to unique and highly sensitive communities of animals, are characterized by extremes in environmental conditions (low temperatures, high pressures), and are exceedingly challenging regions in which to work safely. Deepwater Horizon (DWH) was the world’s first and largest ultra-deep water well blowout and likely not the last. In the wake of that incident, scientific research and industrial development have been focused to better understand the ultra-deep domain, to lessen the likelihood of accidents there, and to better respond to future incidents. This volume summarizes trends in the development of ultra-deep drilling, synthesizes the state of knowledge relevant to ultra-deep oil spill prevention and response, and contrasts the effects of simulated ultra-deep spills in the frontier regions of the Gulf and elsewhere. Recommendations for additional research and public policy changes to lessen the likelihood and impacts of future spills and to improve oil spill response are provided.

Rachel Carson’s 1962 landmark book, Silent Spring, describing the toxic effects of the persistent organic pesticide, DDT, was instrumental in bringing awareness to the notion of environmental pollution (Carson, Silent spring. Houghton Mifflin, Boston, 1962). This work was a catalyst that began the advancement of the global environmental pollution movement and the concern for persistent chemical pollutants (POP). By intentional design, POPs are chemically nonreactive and are resistant to degradation in aerobic environments. It is important to realize that oil pollution and toxicity derived from the polycyclic aromatic hydrocarbon (PAH) components in crude oil are fundamentally different from the chemistry of persistent organic pollutions and its bioaccumulation and magnification that were learned in the 1960s and 1970s. Petroleum hydrocarbons are not stable; they are, in fact, quite reactive in aerobic environments via microbial (Varjani, Bioresour Technol 223:277–286, 2017; Atlas and Hazen, Environ Sci Technol 45:6709–6715, 2011; Salminen et al., Biodegradation 15:29–39, 2004; Widdel and Rabus, Curr Opin Biotechnol 12:259–276, 2001) and photochemical (D’Auria et al., J Hazard Mater 164:32–38, 2009; Plata et al., Environ Sci Technol 42:2432–2438, 2008; Garrett et al., Environ Sci Technol 32:3719–3723, 1998; Overton EB, Laseter JL, Mascarella SW, Raschke C, Nuiry I, Farrington JW (1980) Photochemical oxidation of IXTOC I oil, pp 341–383. In: Proceedings of symposium on preliminary results from the September 1979 Researcher/Pierce IXTOC I Cruise. Key Biscayne, Florida, June 9–10, 1980, NOAA Office of Marine Pollution Assessment, Boulder, CO) oxidations. To understand the implications of oil spills, we need to recognize that we are dealing with the reduced form of a pollutant that can readily react in most of the environments. The goal of this chapter is to present the dynamics of an oil spill from the molecular level with a description of the carbon cycle, the role of photosynthesis, diagenetic production of oil, its ultimate conversion back to carbon dioxide, and the fundamental carbon cycle processes in environmental chemistry. Only by understanding what happens chemically to spilled oil can we accurately predict and understand the biological consequences of these spills and the harm done by exposures to hydrocarbons from oil.

This chapter provides a summary of the scientific knowledge about sediments and fauna in the margin of northwest Cuban shelf. Little scientific information is publicly available, and so much of what is discussed here is the result of the scientific expedition to the region in May 2017 on board the R/V Weatherbird II as part of the GoMRI consortium, C-IMAGE (see Foreword, this book). The goal was to set broad environmental baselines against which to evaluate the impacts of any potential future oil spill or other disturbance in the Gulf of Mexico (GoM). The chapter is organized in three parts: (1) overview of the geographical setting of Cuban margin of GoM; (2) sediment characterization including texture, composition, and geochronology of sediment cores; and (3) characterization of key bioindicators of oil impact: mollusks, meiofauna, and foraminifera.

Benthic ecosystems often act as a repository for oil contamination that washes ashore or is deposited onto sediments following a major oil spill. Sedimentary microorganisms mediate central ecosystem services on the coast, such as carbon and nutrient cycling, and these services may be adversely impacted by oil perturbation. Thus, during the response to the Deepwater Horizon (DWH) oil discharge in the Gulf of Mexico, considerable effort went into characterizing the response of benthic microbial communities to oil deposition on shorelines of the Northern Gulf where oil came ashore. Oil perturbation elicited a pronounced microbial response in coastal ecosystems, altering the abundance, diversity, and community composition of sedimentary microorganisms. Next-generation gene sequencing and metagenomic approaches, which were not available during previous large oil spills, have revolutionized the field of microbiology, providing new insights into the microbial response after the DWH discharge. This review centers on a case study of the fate of oil contamination in Pensacola Beach sands, which sheds light on the mechanisms of microbially mediated hydrocarbon degradation and the impacts of oiling to ecosystem functions. Analysis of field and laboratory results is discussed along with the technological advances that made these observations possible. Metagenomics enabled the application of ecological theory, thereby building a stronger foundation for the effective prediction of baseline microbial community structure/function and response to oiling. Oil perturbation was shown to resemble a press ecosystem disturbance according to the disturbance-specialization hypothesis. Benthic microbial communities were shown to be resilient, maintained ecosystem functions, and recovered quickly after oil disturbance.

After the Deepwater Horizon (DWH) oil spill, interest in marine animal movement was heightened by recognition that some individual animals had been cryptically exposed to the oil, and that some of these exposed individuals later moved, introducing oil contamination to geographic areas that were beyond the initial domain of direct oil impact. Forensic methods based on internally recorded stable-isotope records can be used to address the issue of movement by contaminated individuals. Different tissues provide stable-isotope histories that reflect different periods in the individual’s history, ranging from just a few recent days in the case of blood plasma to the entire lifetime in the case of eye lenses and otoliths. Isotopic offsets between tissue types (e.g., liver and muscle) within the same individual can be used to measure the relative site fidelities of different individuals. Among individuals that have low site fidelity, geographic movements can be estimated by comparing lifetime isotope trends with background maps of isotope variation (isoscapes). The process of isotope conservation within the vertebrate eye lens is described, and practical application of forensic methods and data interpretation are discussed.

The lack of baseline data has hindered the assessment of impacts from large-scale oil spills throughout their history. Baseline data collected before an adverse event such as an oil spill are critical for quantifying impacts and understanding recovery rates to pre-spill levels. In the case of the two largest oil spills in the Gulf of Mexico (GoM), Deepwater Horizon and Ixtoc 1, the lack of comprehensive contaminant baselines limits our ability to project when the ecosystem will return to pre-spill conditions and assess the short- and long-term impacts of contamination on ecosystems. Beginning in 2011, we initiated comprehensive sampling in the GoM to develop broad-scale and Gulf-wide hydrocarbon contaminant baselines primarily targeting continental shelf fishes in the USA, Mexico, and Cuba. We also developed a time series of collections over 7 years from the region in which DWH occurred. In the event there is another oil spill in the GoM, the samples from these baselines will provide broad-scale but not installation-specific baseline information for the assessment of impact and recovery. This chapter provides a summary of historical sampling and current baseline data for pelagic, mesopelagic, and demersal fish in the GoM. Further, we outline the importance of ongoing and more specific collection of monitoring data for hydrocarbon pollution.

As deep-sea oil exploitation increases worldwide, the probability of another Deepwater Horizon (DWH) blowout also increases. The DWH disaster directly impacted the coastal communities of the Gulf of Mexico (GoM) with 11 deaths and the release of 172.2 million gallons of gas-saturated oil, covering over 1000 miles of coastline and contaminating an estimated 300,000 million cubic meters of GoM water. In the aftermath of the DWH blowout, the question of what a similar event would look like outside the GoM is of fundamental importance. Anticipating the extent and potential environmental impact of major spills in other locations becomes important for effective oil preparedness and response, including coordination of emergency response between neighboring countries. Avoiding deep-sea drilling in environmentally sensitive and some of the world’s most biodiverse and productive fishing areas is also of upmost importance. The west coasts of Cuba and West Africa may be two of the most environmentally sensitive areas across the North Atlantic, yet exploitation of deepwater oil reservoirs has already started or is imminent. Northwest Cuba holds abundant coral reefs characterized by uniquely high diversity and fish biomass, and the region is also home of multi-species spawning aggregations, crucial for the persistence of fish populations. In addition, this area contains Cuba’s most important lobster fishery grounds. A major oil spill occurring in NW Cuba is thus likely to have deleterious impacts on the biodiversity and seafood resources of the region. The West African coastal upwelling system is an extremely productive area, harboring one of the world’s main “hot spots” in terms of fish abundance and biomass. This important system is most likely also a crucial mechanism regulating the climate, and an oil spill in this area could thus have severe local and global impacts.

The ever-growing increase in deep-sea oil explorations in the Gulf of Mexico (GoM) has been raising concerns with regard to future oil spills. Major oil spills in the GoM such as the Deepwater Horizon (DWH 2010) and the Ixtoc 1 (1979) resulted in extensive pollution of the pelagic, sea-floor, and coastal ecosystems. Oil spill transport and fate models are effective tools which allow a spatiotemporally explicit reconstruction of oil spills, while accounting for key processes such as evaporation, sedimentation, biodegradation, and dissolution. Oil transport data can be fed into an ecosystem model to help estimate system-scale changes in biodiversity and impacts on the delivery of ecosystem services. The increase in deep-sea oil-drilling endeavors warrants an evaluation of the potential outcomes and effects of oil spills. However, each spill scenario is a complex 4-D problem, spanning over wide spatiotemporal dimensions, affecting various media (water, sediments, coast, air); hence it is difficult to effectively evaluate the differences between various oil spill scenarios.

A MOSSFA (marine oil snow sedimentation and flocculent accumulation) event was the reason that substantial amounts of the spilled oil were transported to the seafloor during the Deepwater Horizon (DWH) oil well blowout. The region-wide sinking and flocculent accumulation of marine oil snow on the sediment surface changed redox conditions, slowed down the biodegradation of the oil, and increased the spatial and temporal impacts on the benthic community and habitat suitability. Recent field research has confirmed that, in addition to the DWH MOSSFA event in the northern Gulf of Mexico (nGoM), another extensive MOSSFA event occurred in a biologically sensitive area in the southern Gulf of Mexico (sGoM) during the 1979–1980 Ixtoc 1 oil well blowout. Thus, MOSSFA events are not unexpected and have the potential to not only alter sediment chemical conditions but also to extend, expand, and intensify the ecological impact of an oil spill. Consequently this risk should be taken into consideration when preparing response strategies for potential future oil spills and subsurface oil well blowouts. To illustrate this approach, MOSSFA-sensitive areas were identified in offshore areas where deepwater oil production and exploration are occurring. Based on the newly gained insights into the factors that can initiate and contribute to a MOSSFA event, global maps showing the presence of oil/gas platforms, phytoplankton biomass, and suspended mineral matter are developed in order to infer the probability that future MOSSFA events are likely to occur. These maps are of particular importance for oil spill responders who will be deciding locations and which oil spill response strategies (i.e., applying large volumes of dispersants, burning in situ burnings, increasing riverine inputs of nutrients, and fine-grained clay particles) would result in the development of a MOSSFA event.

During the Deepwater Horizon (DWH) oil spill, extensive areas of the Gulf of Mexico (GoM) were closed for fishing due to the risk of seafood contamination and fishers’ health. The closures were determined daily according to the estimated extent of the spill relying mainly on satellite imaging. These closures were largely limited to the northern GoM. Yet, evidence from the field indicates a presence of oil beyond the closures, in some cases at toxic concentrations. With the advancement of oil transport modeling, together with the availability of new in situ data, we examine the 4D extent of the DWH spill, along with the effectiveness of the fishery closures in capturing the oil spill extent. We use the oil application of the Connectivity Modeling System (oil-CMS), cross-checked against in situ BP Gulf Science Data (GSD) and other published studies. The oil-CMS indicates that DWH extended well beyond the satellite footprint and fishery closures, with the closures capturing only ~55% of the total extent of the spill. With an increasing global shift toward deep-sea drilling, our findings are important for the safety of coastal communities and marine ecosystems around deep-sea drilling areas.

The Deepwater Horizon (DWH) oil spill may be indicative of future large, deep spills that may occur in the coming decades. Given that future deepwater spills are possible, critical considerations include (1) establishing baselines for oceanic marine mammal and populations in at-risk areas, (2) understanding the implications of response choices for oceanic marine mammals, (3) designing studies with adequate coverage for post-spill monitoring, and (4) identifying effective strategies for oceanic marine mammal restoration. In this chapter, we consider these four stages in the context of a series of hypothetical oil spill scenarios, identifying ways that lessons learned from the DWH oil spill and prior events can be applied to future disasters.

Mitigation options for deep-sea oil spills are indeed few. In the open ocean, far from land, booming, burning, and mechanical pickup of oil at the sea surface may be of limited value due to wave and wind conditions. The use of chemicals to disperse oil into smaller droplets is predicated on the assumptions that smaller droplets are more easily dissolved into surrounding waters and that smaller droplets are degraded by bacterial action more rapidly than are larger droplets. During the Deepwater Horizon accident, a novel use of dispersants injected directly into the subsurface source of the blowout was undertaken to treat the oil prior to surfacing. The presence of subsurface “plumes” of small droplets and dissolved oil observed during DWH raised the issue of active measures to sequester oil in the subsurface vs. allowing it to surface. Reducing the concentration of volatile organic compounds surfacing near workers was also a stated objective of subsurface dispersant injection (SSDI) application. Aquatic toxicity testing has evolved significantly from a sole focus on short-term mortality to evaluate a variety of sublethal physiological, genotoxic, and immunogenic impacts affecting animal health and fitness of exposed populations. In this chapter we consider a number of pressing – and heretofore unresolved – issues surrounding the use of dispersants as an oil spill mitigation tool. Further, we advocate continued, targeted research to help resolve ongoing controversies regarding dispersant use.