The growing energy demand in industrialized North America, as in the rest of the world, has been satisfied mostly by use of fossil fuel hydrocarbons. As consumption, exploration, transportation, and production of hydrocarbons offshore and in coastal areas have increased, scientists have recognized and studied impacts of oil in the sea. Regulators have implemented new requirements, spill responders have developed innovative techniques, and the industry has employed updated operational practices and safety measures to limit the impact on the marine environment. Although significant progress has been made to better understand and reduce quantities and effects of oil in the sea, the risks have not been eliminated. A serious reminder of this was the 2010 Deepwater Horizon (DWH) disaster, an explosion that resulted in the largest oil spill in North American waters.
With the support of many agencies and industry, the National Academies published reports in 1975, 1985, and 2003 on inputs, fates, and effects of petroleum-based hydrocarbon mixtures in the sea, both from natural sources and human activities. The reports assessed the scope of the challenge and made recommendations for improvement in oil spill science, prevention, and mitigation of the impact of harmful discharges on the environment, and for reduction of inputs from operational and accidental discharges. This study is the fourth report in a series. Nearly two decades have passed since the third report was released, over which time there have been significant advances in technology and science. There are almost 20 additional years of research on long-term effects of oil spills on the environment from incidents such as the Exxon Valdez oil spill and six large (more than 10,000 barrels) spills in North American waters, including the DWH explosion and oil spill.
The Committee on the Oil in the Sea IV was appointed to document the current state of knowledge of sources, volumes, fate, and effects of oil entering the marine environment; to identify important gaps in research and understanding in each of those areas; and to make recommendations on reducing the inputs into the sea and the effects of oil on the environment (the Statement of Task is included in Chapter 1, Box 1.2). The committee’s deliberations and report writing were informed by review of scientific literature and by a series of public meetings and presentations, drawing in expertise from academic, governmental, and non-governmental communities.
SOURCES OF OIL IN THE SEA
The life cycle of “oil in the sea” starts with the input of oil to the marine environment. Oil enters the sea from a variety of sources, including:
- natural oil and gas seeps;
- extraction of petroleum (spills from production and drilling platforms, deposition from platform air emission, produced water, and gas condensate discharges disaggregated by platform type [e.g., deep water, ultra-deep, shallow waters, leaks associated with platform decommissioning]);
- transportation of petroleum (pipeline spills, tanker spills, operational discharges, coastal facility spills, deposition from tanker exhaust and volatile organic carbon [VOC] emissions); and
- consumption of petroleum (land-based runoff, recreational vehicle discharge, spills from commercial vessels, operational discharges from commercial vessels, atmospheric deposition from land-based sources, aircraft dumping during emergencies).
The past 20 years have brought many changes to the ways in which oil and natural gas are extracted, transported, and consumed. The North American energy landscape has changed with the production of shale oil and natural gas both in the United States and Canada. In the past, the United States was a net importer of hydrocarbons, but now, because of the increased production and changes in legislation allowing export of crude oil, the United States has become an exporter
of crude oil and natural gas, which has had an impact on terminals and on shipping routes.
Increased urban populations in coastal areas, changes in consumer behavior, improved fuel efficiency of vehicles, and introduction of electric cars are all impacting land-based consumption and, although more difficult to quantify, inputs of oil into the sea.
Other major changes that have had an impact on inputs of oil entering the sea since the Oil in the Sea III report include new regulations on design and operation of ships carrying hydrocarbons as cargo or as fuel, and on engines used on recreational vessels. Following the DWH oil spill, major changes were introduced to the regulations governing offshore oil and gas operations, and major advances were made in blowout prevention and source control. New performance measures and enforcement mechanisms have been introduced to improve pipeline safety. In general, there is an increased focus on improving the safety culture in the oil and gas as well as in the shipping industry.
Although specific data are lacking for estimating many inputs of fossil fuel hydrocarbons into North American waters, enough data do exist to understand recent trends and, in many cases, to provide more precise estimations of annual volumes. Overall, looking at oil inputs to the sea from 2010 to 2019, as compared to previous reported estimates from 1990 to 1999, if the DWH oil spill event had not occurred, it could be concluded that regulatory changes, advances in science and technology, and, for the most part, attention to safety have helped to reduce the amount of oil pollution in North American waters.
However, there are also new potential sources for oil pollution in North American and global waters related to the aging infrastructure in the sea and along the coasts, deteriorating shipwrecks releasing oil, sea-level rise and increased intensity and frequency of storms, use and transport of new types of oil, changes in shipping routes including travel through arctic regions, shifts in workforce, expertise and asset ownership in the energy industry, warfare, and others.
The committee’s best estimates of the mass of oil entering the sea through natural sources, land-based sources, operational discharge, and accidental spills are shown in Figure S.1 (refer to Chapter 3 for details on the estimates). The general trends are described below:
- The estimates of land-based sources by far outweigh other sources, even when including the DWH oil spill and worst-case projections for the Mississippi Canyon 20 oil spill in the estimates. Land-based runoff was calculated using the same approach as Oil in the Sea III and is based on several assumptions; it is therefore not possible to determine the quantitative increase with confidence; however, these estimates are in line with global estimates (which are closer to 30 times higher than those reported two decades ago in Oil in the Sea III).
- The second highest input is from natural oil seeps. The committee’s estimates of natural seeps are roughly one-third lower than reported in Oil in the Sea III, and reflect updated estimates for the Gulf of Mexico; new data are not available in other North American regions.
- Spills represent the third highest input, even when including an annualized estimate for the DWH oil spill. In North America, spills occurred more frequently in offshore waters than nearshore waters and predominantly in the Gulf of Mexico. Over 20 years, the volume of spills decreased significantly for pipelines, tank vessels, non-tank vessels, and coastal refineries.
- The other major source is operational discharges, which, in this report, include produced water from offshore oil wells and discharges from machinery operations on commercial vessels. Assuming full compliance of regulations, all discharges from commercial vessel operations are small, less than 10 metric tonnes per year. Although it can be safely assumed that discharges from recreational boating greatly decreased with regulatory actions to ban sales of the two-stroke engine, there are no data available for estimating actual discharges of oil in the marine environment from this source. Produced water estimates are higher in total than they were 20 years ago, reflective of increased offshore hydrocarbon production.
It should be noted that not all sources of oil in the sea are equal in terms of impact on marine life; chronic or continuous inputs have very different effects on the environment than accidental spills. The volume and the rate of discharge, as well as other factors, are important for determining both the fate and the effects of the oil in the marine environment.
This report also recognizes “that there was a significant lack of systematic data collection concerning petroleum hydrocarbon discharges entering the oceans” (NRC, 1975), indicating little progress since the original Oil in the Sea report in 1975 (titled Petroleum in the Marine Environment) and more recently in 2003. While the Oil in the Sea IV committee found more specific data on some inputs (spill volumes, permitted discharges), values in other input categories remain vague (land-based runoff, sewage discharge, two-stroke engines, atmospheric deposition, and emergency aerial dumping) to nonexistent.
More precise estimates of fossil fuel inputs in relation to natural sources such as oil seeps may permit identification of particular anthropogenic inputs that are significant in comparison with local natural inputs, are likely to have adverse effects on marine organisms, and are amenable to efforts to reduce or otherwise mitigate these inputs.
Recommendation: In recognition of decades of inaction on past Oil in the Sea report recommendations to measure natural and anthropogenic oil inputs
to inform mitigation of the effects on the marine environment, the committee recommends that an independent group report on measures and responsibilities of North American agencies to acquire more comprehensive data to better achieve quantification of oil inputs to the sea. The following actions should be taken to improve quantification of oil inputs to the marine environment:
- Federal agencies should work with industry and academia to use existing techniques, along with exploration of new technologies, for identification and quantification of inputs from natural seeps including less recently studied areas such as the North American Pacific margin, North American Arctic margin, and newly discovered seeps in the North American Atlantic margin. Priority should be given to areas with offshore energy exploration and production and along marine shipping routes to better assess background levels of oil in the sea and inform damage assessment.
- Federal agencies should work with state and local authorities to undertake regular monitoring of oil inputs from land-based sources of water (runoff, rivers, harbors, and direct ocean sewage discharge) to determine oil inputs into marine environments.
- Federal agencies should support research to refine estimates of land-based inputs of oil that are transported via the atmosphere to the sea (including fuel jettison) by expanding the geographic and temporal coverage of data collection, and by refining understanding of the source of hydrocarbons measured in marine atmospheres and surface seawater.
- Relevant agencies should work with industry to gain a better understanding of composition and concentrations in produced water (from offshore exploration and production activities) released into the marine environment and implement practices to reduce potential environmental impacts of these discharges.
- A study should be conducted on the level of the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex I compliance to establish a baseline to monitor changes in compliance.
PREVENTION OF OIL IN THE SEA
Because land-based runoff is a significant source of oil in coastal seas (resulting largely from urbanization and an increase in the number of vehicles in operation), preventative measures could include initiatives to improve capture and processing of stormwater and sewage discharge, reduce gasoline vehicle usage (e.g., carpooling, increased use of public transportation), and continue improvements in fuel efficiency and increase usage of electric vehicles, as well as improving car maintenance and the replacement of older vehicles.
Advances have been made by industry and federal and state agencies in developing and implementing technologies and best practices for preventing accidental spills from onshore and offshore pipelines and facilities and marine transportation.
Recommendation: During the transition to more renewable energy sources, the following steps should be taken by industry and by federal and state agencies to prevent future spills in North American waters:
- Consistent with previous reports, government and industry should continue their efforts to develop and implement technologies and best practices to prevent and reduce the magnitude of accidental spills from onshore and offshore pipelines and facilities and marine transportation. The committee recognizes the risk of complacency following periods of reduced spillage and advises government and industry to maintain vigilance.
- Government should review whether the technical recommendations arising from the extensive investigations in the aftermath of the DWH oil spill regarding blowout preventers, operational issues, and safety culture have been implemented, and identify those that have not yet but could be implemented.
Government should conduct a comprehensive review of the integrity of coastal onshore and offshore energy infrastructure to determine if it can withstand increased frequency and intensity of extreme weather events and other natural hazards. This should involve:
- review and update of design criteria for extreme events in light of new data;
- assessment of modifications to existing structures needed to prevent or mitigate damage or spillage of oil resulting from extreme events; and
- development of response plans and corresponding response capabilities to reduce and mitigate spills in case of damage due to extreme weather events.
- To mitigate potential spills from aging infrastructure, appropriate agencies should take inventory of the existing remnants of oil storage, transport, or production activities that still need to be identified. Salvage or capping of these facilities should be prioritized based on the potential impact if the infrastructure fails.
- In order to maintain response readiness, government should assess the economic and environmental impacts of changes in marine vessel transportation on pollution risk, such as introduction of new fuel types, increased vessel size, new types of cargoes (liquefied natural gas, other gases, biofuels, and diluted bitumen), and new traffic patterns and offshore infrastructure.
MINIMIZING THE EFFECTS
While much is done to prevent and reduce amounts of oil entering the sea, accidental spills occur and will continue so long as there is offshore production and transportation of oil. In the event that a spill does occur, it is important to have tools available, and plans in place to most effectively respond to the spill and to protect the vulnerable.
Recommendation: The following steps should be taken to minimize the effects of oil entering the sea:
- Regulatory mechanisms should be introduced to encourage evaluation, permitting, and deploying of new advanced response techniques when they become available. The use of these techniques during actual emergency response should be guided by the specific scenario to ensure they add value and maximize health, safety, environmental, cultural, and socioeconomic protection.
- Appropriate responsible agencies should plan for effective ways for rapid scientific response to oil spills to enable scientists to mobilize to the field quickly and in concert with response operations. This should involve rapid communication and approvals between all parties to define the operationally relevant scientific direction and gather relevant information for future decision making with respect to minimizing the effects of the spill.
- Large oil spills contaminating productive marine ecosystems and shorelines may inflict mass mortalities on vulnerable species such as seabirds, marine mammals, and shoreline biota and disrupt the ecology in that location. Following a spill, appropriate environmental specialists (e.g., a specialist in the Incident Command System [ICS]) should promptly identify these species, ecological linkages should be promptly identified, and their abundances in the affected region should be monitored, to enable detection of these indirect effects on populations at the community level and ensure their protection.
ADVANCES IN OIL SPILL SCIENCE
Understanding the Fates of Oil in the Sea
In the past two decades, there has been major progress in understanding fundamental physical, chemical, and biological processes and reactions that influence the fate of oil in the marine environment. Significant advances have been made in the following areas:
- The interactions of live oil and gas spilled within the ocean water column are better understood.
- Gas bubble sizes and oil droplet breakup processes for oil released into the sea, critical to determining their fate and ultimately determining the affected environments, can be more accurately predicted.
- A new phenomenon, “tip streaming,” responsible for creating micro-scale droplets, has been identified for droplets treated with chemical dispersant, allowing threads of oil to leak into and break within the droplet wake.
- Ongoing advancements in data storage platforms and computing capabilities have enabled profound advances in computational fluid dynamics modeling of oil spills in the oceans.
- Dissolution, long known as a relevant fate process for oil spilled at the sea surface, has been recognized as potentially significant for subsea oil spills, such as accidental oil well blowouts.
- Research on optimal design, implementation, and efficacy analysis of subsea dispersant injection (SSDI) was employed as a response option during the DWH oil spill. These analyses showed that even modest changes in oil droplet size distributions may lead to significant changes in the fate and effects of the spilled oil and may significantly benefit human health by reducing volatile organic carbon emissions to the atmosphere from subsea spills.
- There is renewed appreciation of the importance of photo-oxidation by solar irradiation of oil at the sea surface and near-surface as a major pathway for oil degradation. Numerous direct and indirect photooxidation reaction products likely influence the fate and toxicity of spilled oil.
- Marine oil snow sedimentation and flocculant accumulation (MOSSFA), a phenomenon observed in the Gulf of Mexico, has been proposed as a mechanism to explain observed oil transport to the seafloor during and after the DWH oil spill.
- There is an expanded appreciation of processes and oil fates unique to cold water and sea ice in deep sea and Arctic environments, and new recognition that oil biodegradation can occur at rates faster than previously assumed at near-freezing temperatures.
Understanding the Effects of Oil in the Sea
Understanding of exposure to and ultimately the acute and chronic effects of oil pollution on marine and estuarine habitats and resident organisms has significantly expanded and improved since the publication of Oil in the Sea III in 2003. Highlights include:
- The identification of new exposure scenarios (i.e., routes and/or specific chemical components involved), toxicity mechanisms of action, target sites and biological effects, mixture toxicity, environmental modifiers of toxicity (e.g., UV light, pressure), new biological receptors, impacted habitats and species, and long-term implications from direct or indirect exposure to oil spills.
- There have been significant advances in resolving the complexity of determining or predicting the effects of petroleum hydrocarbons in the marine environment within a changing ecosystem and multiple co-stressors using field, laboratory, or predictive modeling-based approaches.
- New knowledge of oil toxicity with “natural” lower-level exposures via respiration/absorption includes the chronic effects on the hypothalamic-pituitary-adrenal axis (at least in marine mammals), immune system in many higher-level vertebrates, and an organism’s microbiome (external and/or internal), which may influence the overall health of the exposed organism.
- Biotechnology ‘omics1 tools have also been developed to detect target sites and mechanisms of action for oil toxicity and as biomonitoring tools for use in baseline studies, damage, and recovery assessments.
- There has been tremendous growth in the examination of the potential effects of oil spills on human health, including mental and behavioral effects; and considerations of socio-economic impacts and community resilience as well as the potential direct toxicity to humans of crude oil, its components, and derivatives.
COMMON THEMES FOR ADVANCING OIL SPILL SCIENCE
Complex and intrinsic interdependencies exist among inputs, fates, and effects and the measures to reduce them, either from the source or by response. Recognition of this interdependency accompanied by best practices with respect to oil spill science in general led to the emergence of several repeated themes throughout the report for advancing understanding of oil spill science, all with the end goal of minimizing negative impacts to the environment by better informing prevention, response, and restoration activities.
Long-Term Funding for Inputs, Fates, and Effects of Oil in the Sea
The Gulf of Mexico Research Initiative (GoMRI), a 10-year program initiated after the DWH oil spill, resulted in an extraordinary output of both discipline-specific and multidisciplinary research by funding a mix of field, laboratory, mesocosm, and test facility science and related modeling. Advancement of oil spill science has a history of being hindered by a boom-and-bust funding cycle and, consequently, the inability to sustain research and the scientific expertise to conduct the research.
Recommendation: As recommended in Oil in the Sea III, there remains a need for long-term, sustained funding focused on oil in the sea to support multi-disciplinary research projects that address current knowledge gaps, including those listed as Research Needs throughout this report. Research is needed to address new regulatory requirements and to improve response capabilities. The application of new data and technologies to advance interdisciplinary knowledge of fates and effects of oil in the sea will require a longer funding commitment than is currently typical.
Open Water Experimentation and Use of Spills of Opportunity
Government agencies, industry, private companies, nongovernmental organizations, and academia are continually looking into improvements to response technologies, identifying the effects of oil on the environment, developing better ways to monitor oil in and on the water, and looking for ways to increase the efficiency of response operations and organizations. These projects generally take place in a laboratory or test tank. It is not possible to simulate all the complexities and variability of field conditions in a small-scale or large-scale laboratory setting alone. Field experiments with real oil and studies conducted during actual response events are critical for understanding the fate and behavior of oil in realistic conditions and for the development, testing, and improvement of response techniques.
Recommendation: As recommended in previous reports, controlled in situ field trials using real oils should be planned, permitted, and funded to incorporate multi-disciplinary research focused on important processes as well as response techniques that do not accurately scale from in vitro or ex situ experiments to in situ conditions. Additionally, funding and systemic mechanisms should be set in place by appropriate agencies to enable rapid deployment of qualified scientific personnel during actual oil spill events (i.e., spills of opportunity) to conduct appropriate, time-critical research in situ, outside the Natural Resource Damage Assessment process, while having minimal or no interference with spill response activities.
Baseline Knowledge and Data
After a spill has occurred, assessment and research efforts often do not have appropriate or requisite pre-spill data for comparison with post-spill observations and assessment of remediation. This limits the ability to assess the inputs, fates, and effects of oil in the sea.
Recommendation: There is a need to review how pertinent knowledge and data from numerous sources are most effectively assembled, made available, and archived, given the advances and gaps in understanding noted in this report.
- The review should assess what is needed for baseline knowledge and data with recognition that both
1 Meaning genomics and related biomolecular analyses.
- natural and anthropogenic influences (other than inputs of oil) result in baselines that are dynamic in space and time.
- Funding should be established for appropriate baseline data acquisition and curation in locations of particular interest, such as coastal areas, areas with offshore energy exploration and production, and marine transportation routes.
- Data collections would include aspects such as physical oceanography, biogeochemical processes, contaminant source surveys, critical species (e.g., endangered, abundant, and vulnerable, or of commercial importance) and marine biodiversity, and pertinent metrics of human health and well-being.
- As a corollary, guidelines should be developed for collecting and analyzing baseline data immediately after and in the midst of a spill from neighboring, unaffected (control) areas, where possible.
- U.S. Interagency Coordination Committee on Oil Pollution Research (ICCOPR) member agencies, in cooperation with relevant agencies from Canada and Mexico and other interested parties, should convene a series of regional workshops and studies to inform the most efficient process of defining and assembling the evolving baseline knowledge and data. These workshops should gather relevant knowledge from stakeholders such as Indigenous peoples; diverse rural, suburban, and urban coastal communities; government agencies; business and industry; nonprofit groups; and the academic sector.
Big Data and Interdisciplinary Research
Enormous streams of data have been generated from advances in analytical techniques, particularly in petroleum and environmental chemistry and in ‘omics. Archival and maintenance of this “big data” to make it universally accessible is essential for meaningful interpretation of the data and to support interdisciplinary research linking oil chemistry to the fates and effects of the oil in the environment to inform response.
Recommendation: A free, central, universally accessible and curated repository should be formed for information pertinent to oil in the sea in order to better manage the enormous data sets being generated through advanced chemical analyses, ‘omics techniques, geoscience surveys (among others), and especially field and laboratory studies pursuant to oil spills. Optimum use of such archives will require development of data analytics, data quality control, and reporting standards for associated metadata to enable integration and interpretation by, and training of, interdisciplinary teams.
Oil in the Arctic
Marine traffic in Arctic waters is increasing with seasonal decrease in ice cover, and increased offshore oil production is a possibility in the future. Both of these factors could lead to higher risk of oil pollution in the Arctic. Yet, oil spill science in Arctic waters and shorelines has lagged behind study of more temperate and accessible marine ecosystems. Field experiments in Norway, Canada, Alaska, Svalbard, and Greenland have uncovered many complex processes affecting oil in Arctic environments. However, utilizing this information in modeling or response requires additional work.
Recommendation: In agreement with previous reports, there should be a concerted effort to gather information about the fate of oil in Arctic marine ecosystems, with and without ice cover, in advance of further development of this region. This would include baseline surveys (geophysical and biological); efficacy of response and mitigation options; data acquisition on natural attenuation and active remediation strategies, including biodegradation kinetics at low temperature; and effects on higher organisms, populations, and ecosystems in Arctic waters and on shorelines.
New requirements for low sulfur fuel oils (LSFOs) for marine shipping came into effect in 2020, but studies on these oils are currently extremely limited. The few very-low sulfur fuel oil (VLSFO) and ultra-low sulfur fuel oil (ULSFO) samples studied to date differ chemically from traditional marine fuel oils and from each other. To date, insufficient research has been conducted to determine transport and weathering behavior, biodegradability, and toxicity of different LSFO formulations under diverse environmental conditions.
Recommendation: Government should fund research needed to study the composition, toxicity, and behavior of new types of marine fuels (e.g., LSFO, VLSFO, biofuels) and petroleum products (e.g., diluted bitumen) so that fate and effects of these products can be understood and response operations can be planned and executed most effectively to reduce impacts.
The human aspect of oil in the sea permeates each of the decisions made in cleanup activities and endpoints. To that end, it is paramount to understand how oil, as well as oil spills and their responses, may affect human health and welfare. Each response to an oil spill is focused on minimizing harm to the environment. The ultimate clean-up goal is to ensure a healthy ecosystem for a sustainable future, and this
includes both safety measures for those working, living, and recreating along its shores and the sustainability of marine resources such as food, energy, and transportation.
Recommendation: The governmental agencies involved in responding to an oil spill should upgrade the priority and attention given to individual and community mental and behavioral effects and community socioeconomic disruptions in the ICS decision-making and response processes. The inclusion of community-based human health assessment and mitigation measures into the ICS is needed to provide a more holistic approach regarding both human and ecosystem health.
OIL SPILL SCIENCE RESEARCH NEEDS
In addition to identifying overarching recommendations for advancing oil spill science, the report also highlights specific research necessary to better understand the fate and effects of oil in the marine environment, as well to advance response capabilities. Specific research needs are identified for the topical areas of oil spill response and the fates and effects of oil in the sea.
Oil will continue to be a part of the global energy mix, though its share is likely to decrease as the use of alternative energy sources increases. New energy sources and fuels, such as biofuels, ammonia, and hydrogen, can introduce new safety and pollution concerns. The regulators, the research community, and the industry are encouraged to proactively review and address any potential adverse effects from these transitions. The recommendations and research gaps outlined in this report take into account a changing energy landscape. They are critical to address while this transition is taking place, and thereafter, to ultimately reduce impacts of oil on ocean ecosystems and human health and move toward a restorative and sustainable state following both human-caused chronic and episodic releases of oil into the sea.