Since the Deepwater Horizon (DwH) oil spill, numerous research teams, many funded by GoMRI, have spent considerable resources developing modeling tools, collecting and analyzing measurements, and performing scientific studies to understand different aspects governing the eventual fate of the oil. This has resulted in more than 12,800 articles (including peer-reviewed and non-reviewed articles, listed in a Googletm Scholar search) referencing the spill. Together, these data have provided the basis for development of vastly improved modeling tools for tracking the distribution and chemical evolution of oil. But one area where our understanding remains quite limited is the role that microbes play in determining the eventual fate of oil and its impact on ecosystems, and how these processes depend on environmental conditions (hydrographic and biogeochemical properties of the water and circulation), hindering predictive capability.
The overarching goal of this project is to synthesize recent model developments and results from field- and laboratory-based microbial studies in order to fundamentally advance understanding of how microbial biodegradation influences accumulation of petroleum in the water column and in marine sediments of the deep ocean and the shelf, and to investigate the impacts of potential future oil spills under different temperatures, oxygen levels, suspended particulate matter, transport, and bathymetric regimes, all of which would influence biodegradation. The outcomes of this study will provide a more comprehensive analysis of the fate of the Deepwater Horizon (DwH) oil spill than is currently available and improve the ability to forecast the fate of future oil spills. This directly addresses the Gulf of Mexico Research Initiative’s (GoMRI) Research Theme 2, “Chemical evolution and biological degradation of the petroleum/dispersant system and subsequent interaction with coastal, open-ocean, and deep-water ecosystems.”
The DwH oil spill occurred in an area that encompasses a broad variety of oceanographic environments and ecosystems; where microbial activities are quite significant and diverse and where one expects the microbes to strongly influence biodegradation and accumulation of petroleum in the water column and marine sediments of the deep ocean. The DwH spill originated over the deep outer shelf where it could potentially have been transported seaward over the abyssal region of the Gulf of Mexico, or onto shelves of varying width and toward coasts with sandy shores or wetlands. One of the most important components of this area’s circulation, hydrography, and biogeochemistry is the Mississippi River. Among other things, the river supplies nutrients fueling productivity, fresh water that contributes to upper ocean stratification, and sediments that can interact with oil in the water column. Over the Texas-Louisiana shelf to the west, seawater properties (temperature, salinity, turbidity, and currents) are very different than what is found in the deeper location of DwH, and low oxygen (hypoxic) conditions occur each summer. While analysis of the DwH surface oil transport shows that a relatively small fraction of oil from the spill drifted over the Texas-Louisiana shelf, under different forcing regimes, a substantial quantity of the oil could have been advected over this shelf and deposited on the seafloor through sedimentation/flocculation. Additionally, microbial respiration of oil deposited on sediments when hypoxic conditions prevail can further exacerbate low oxygen conditions. Thus, it is critical to have the ability to predict the eventual fate of oil and its impact on ecosystems because toxic oil constituents pose unknown threats to benthic organisms, many of which are harvested in the Gulf of Mexico for human consumption. Additionally, there is an increased likelihood of large spills in the future due to heavy oil and gas extraction activities taking place over the shelf.
This Consortium brings together a select team of investigators with a diverse array of expertise to synthesize their scientific, technological, and data products into a framework that will be used to gain a more complete understanding of the interaction of oil with shelf and deepwater marine ecosystems. Our team will answer questions such as:
- How does the rate of biodegradation of petroleum differ in shelf sediments versus deepwater sediments, and how would this change for locally released (i.e., a shelf spill) oil deposited onto shelf sediments versus aged oil deposited onto sediments on the shelf after advection from a deepwater spill?
- How would the oil delivery pathways differ when the oil spill occurs in a region of high turbidity, such as during a major river discharge event with high sediment, nutrients and freshwater inputs, or during a period of large resuspension associated with storm events?
- How would the biodegradation of petroleum be affected if the spill were to occur, or be advected to, a region experiencing hypoxic conditions?
The specific objectives of this Consortium are to:
1. Integrate recently developed modeling components, including those that simulate large-scale (Gulf of Mexico) circulation, shelf/coastal circulation, three-dimensional oil transport and fate, marine microbial interactions, biogeochemical transformations, and sediment and flocculation processes into a framework for simulating the interaction of petroleum with marine ecosystems from its source along its eventual pathways.
2. Evaluate the system with recent physical, biogeochemical, and sediment observations and microbial processes measurements (including metagenomic and metatranscriptomic datasets).
3. Conduct simulations using the modeling framework of the DwH oil spill and other potential spill scenarios in the region, including similar deepwater releases under conditions that favor transport onto adjacent shallow shelves and coastal areas, oil spills occurring directly on the shelf, spills occurring during cold winter conditions, oil spills in the presence of low oxygen environments, and spills occurring during large river discharge and/or storm events.
4. Perform analysis of the model simulations to address the above questions and gain a better understanding of the interplay between physical and biochemical processes acting on petroleum in the ocean and consequences on deepwater and shelf ecosystems.
The DwH oil spill resulted in an unprecedented commitment to study and better understand different aspects of the fate of oil released in northeast region of the Gulf of Mexico. It is critical to maintain that momentum. This Consortium intends to synthesize the technology, tools, and scientific knowledge of a group of individual investigators some of whom, since the DwH event, have immersed themselves in this study. Additionally, the Consortium brings to the study investigators who can fill critical gaps in our ability to numerically model the transport and fate of oil in coastal waters. As a legacy of this research, the Consortium team will produce a comprehensive framework for simulating and understanding the role that microbes play in mitigating the impacts of oil spills. The model system will be an open source product that can potentially be run in a variety of locations with different physical forcing models. Expected outcomes include the ability to predict the impact of oil spills occurring under different temperature, hydrodynamic, and biogeochemical regimes, a consistently annotated synthesis of genomic and transcriptomic data for the Gulf of Mexico, and the elucidation of mechanisms relating hydrocarbon degradation to microbial community dynamics, flocculation, and sediment transport processes