Patrick T. Schwing

The Deep Water Horizon (DWH) oil spill occurred in the Northern Gulf of Mexico (NGoM) in 2010. Over 700 million liters of oil spilled into the NGoM in the 87 days the wellhead was actively leaking. Samples were taken from sites annually to semi-annually from 2010-2023 to provide a spatial and temporal benthic assessment for the NGoM. Reference conditions provide an ecological snapshot of the marine environment and allow for quantitative assessment of impact and response in the case of future oil spills. Benthic foraminifera, which are single-celled, testate organisms that inhabit the seafloor have proven to be excellent indicators and records of ecological change. Stable carbon isotopes in benthic foraminifera shells (tests) have also proven to be effective indicators of petroleum carbon incorporation into the benthic system. Seafloor sediment cores were most recently collected in 2023, at specific time series sites in the NGoM, as a part of the Scientist-At-Sea program. The sediment cores were subsampled at 2 mm increments. Calcareous foraminifera species, Cibicidoides pachyderma and C. wuellerstorfi, were isolated for stable isotope (oxygen and carbon) analysis using a stable isotope ratio mass spectrometer (SIRMS). Stable isotopes from benthic foraminifera from two of the time-series sites have been measured continually from 2010 to 2017. This study will provide a comparison of the latest benthic foraminifera stable carbon isotopes profiles with previous collections to determine long-term recovery of the system, gain insight into natural variability, and establish long-term preservation of the DWH signal in fossil (downcore) benthic foraminifera tests. These records will continue to aid in the understanding of natural seafloor carbon cycling, and also in the event of future pollution events such as oil spills.

The DWH blowout and Taylor Energy sediment-slump incidents raise questions regarding siting of energy facilities and preparedness for large-scale and long-duration spills. The culmination of 10-years of research supported by the Gulf of Mexico Research Initiative provides important new perspectives related to oil spill preparedness and impact assessment. The DWH, at 1522 mwd, and the release of a light sweet-crude oil was just one of the potential "family of blowouts" that could potentially occur at varying locations. Since oil exploration has continuously gone deeper, with drilling now occurring to at least 2960 mwd, high-pressure testing facilities have been developed to predict oil partitioning, solubility and droplet sizes for blowouts occurring at varying depths oil-types and gas/oil ratios. High-pressure facilities can also be used to determine the efficacy of sub-surface dispersant injection and other oil spill countermeasures. During DWH, under-sea oil plumes rich in BTEX compounds and a regionally-expansive MOSSFA (Marine Oil Snow Sedimentation and Flocculent Accumulation) event caused significant ecological damage resulting in 3-15% of the oil on the seafloor. There are now advance modeling tools to better define intrusion geometry, chemistry, trajectory and fate and to predict MOSSFA events. The lack of environmental baselines for waters, sediments and biota prior to the spills led to equivocation on the extent of impacts. In the event of future large-scale and long-term spills, a broader array of environmental and ecological baselines now will provide the information needed to quantify impacts and assess long-term consequences. Baselines near existing and planned exploration and production infrastructure include, but are not limited to, oil-derived components in waters, important fish species, sediments and benthic ecosystems. Prior to the commitment of drilling exploratory oil wells in regions prone to sub-surface slumping, sediment coring and shallow seismic techniques can identify areas susceptible to and that have experienced geologically-recent sediment slumping thus preventing an incident like that which topple and buried the network of well infrastructure. This talk will review a range of policy recommendations aiming to fulfill this ambitious but necessary endeavor.