The Deepwater Horizon Oil Spill and Marine Mammals
The Marine Mammal Commission has been monitoring closely all aspects of the Deepwater Horizon oil spill, including response, assessment, and restoration efforts. The Commissioners, staff, and scientific advisors are in frequent contact with other federal and state agencies and non-governmental stakeholders with expertise on marine mammals and marine ecosystems, and the potential effects of oil spills on marine mammals. Although oil from the Deepwater Horizon spill continues to be seen in certain areas of the Gulf, federal and state resource agencies have shifted their focus to injury assessment and restoration planning. Determining the short-term and long-term effects of the spill on the ecosystem, including marine mammals, is a primary goal of assessment efforts. This information will be used to determine liabilities for losses to natural resources and ecological services as a result of the oil spill and to guide restoration efforts to ensure that resources are returned to baseline conditions. Baseline conditions are those that would exist had the spill not occurred.
The Commission has actively supported response and assessment efforts, provided information to help understand the potential effects of the spill, and developed recommendations for long-term assessment of effects. To monitor the distribution of marine mammals in the oil spill area, the Commission funded the initial deployment of passive, high-frequency acoustic recording equipment by researchers from Scripps Institution of Oceanography working in collaboration with the National Marine Fisheries Service’s Southeast Fisheries Science Center. In June 2010 the Marine Mammal Commission testified before Congress regarding the Deepwater Horizon oil spill and its effects on marine mammals. The Commission’s testimony summarized potential short-term and long-term effects, how these effects will be assessed, and the likely impact of oil and gas activities on marine mammals in the Gulf and elsewhere. In August 2011 the Commission submitted to Congress a statement of research needs to assess the long-term effects of the spill on marine mammals. The Commission will continue to work with federal and state resource agencies and non-governmental stakeholders to review response and assessment efforts. The Commission also will continue to track and facilitate efforts to recover and restore the Gulf ecosystem.
Marine Mammals at Risk in the Gulf of Mexico
Stock assessment reports compiled by the National Marine Fisheries Service identify 21 marine mammal species under its jurisdiction that occur in the Gulf of Mexico, comprising 57 stocks, 37 of which are bottlenose dolphin stocks. In addition, the Fish and Wildlife Service is responsible for one species of marine mammal that occurs in the Gulf of Mexico, the Florida manatee.
Marine mammal species and stocks in the Gulf of Mexico
Baseline information for these species and stocks is limited. For example, abundance estimates for only 5 of the 57 Gulf of Mexico stocks (or stock groups) listed in the National Marine Fisheries Service's 2010 stock assessment reports meet the Service's own standards for acceptable precision (i.e., a coefficient of variation equal or less than 0.3 for the best population estimate). The lack of information will make it difficult to determine what changes have occurred as a result of the spill, if any, in population size, distribution, habitat use, and other aspects of marine mammal demography and ecology.
Potential Effects of Oil Spills on Marine Mammals
All marine mammal stocks in the Gulf may have been, or may still be, affected by the Deepwater Horizon spill. All effects are initially manifested at the individual level, and must lower the individual’s probability of survival or reproduction to affect the population. The effects may be direct (e.g., contact with oil or dispersants, interactions with response activities) or indirect (e.g., degradation of habitat, reduced availability of prey).
Potential physiological or behavioral effects of concern include:
Observed Impacts from Previous Spills and Studies
The available information on the effects of oil on marine mammals is limited. Current understanding is based primarily on information from the Exxon Valdez oil spill, other oil spills, a small number of controlled exposure studies, simulations and in vitro studies, and observed effects of exposure on non-marine mammal species. Available information does not allow for a prediction of the severity of either short- or long-term effects of the Deepwater Horizon spill on marine mammals. However, available information does provide ample evidence that exposure to oil can harm marine mammals. For example:
Deepwater Horizon Oil Spill
The Deepwater Horizon oil spill presented a number of unique challenges, as compared to other spills in U.S. and international waters:
Response and Assessment Activities
The government's response to affected wildlife (e.g., mammals, sea turtles, and seabirds) followed procedures established for this spill by the Wildlife Branch of the Deepwater Horizon Unified Command. Under this structure, the National Oceanic and Atmospheric Administration (NOAA) and the Fish and Wildlife Service worked with the Oiled Wildlife Care Network to coordinate the Gulf marine mammal stranding network, revise NOAA’s marine mammal response guidelines to address Gulf species, train stranding responders regarding hazardous materials and chain-of-custody protocols, and distribute sampling supplies.
Surveillance and various operational crews and the public were able to report injured and stranded wildlife to the Wildlife Branch via the Wildlife Hotline and other means. The Wildlife Branch provided daily summary reports of stranded wildlife in the area affected by the oil spill on the Restore the Gulf web site, and the locations of stranded animals were posted on the NOAA GeoPlatform web site. More detailed information on marine mammal and sea turtle strandings, as well as general information on response activities and effects of oil on marine mammals and sea turtles, were posted on NOAA's Office of Protected Resources Gulf of Mexico oil spill web site.
The Oil Pollution Act of 1990 was passed after the Exxon Valdez oil spill and addresses liability for losses to natural resources and services caused by the discharge or substantial threat of discharge of oil. Designated trustees (federal, tribal, and state agencies) are charged with conducting a Natural Resource Damage Assessment after an oil spill or other discharge event. The assessment consists of collecting and analyzing information to evaluate the nature and extent of injuries resulting from the incident. Trustees then determine the restoration actions needed to bring injured natural resources and services back to baseline conditions and make the environment and public whole for interim losses. BP and the other responsible parties are then expected to pay the costs of natural resource damages (including the costs of assessing such damage) and compensate the public for lost services derived from those natural resources.
To assess damages and plan restoration, the Trustees must compare the best available baseline information on conditions before the spill against information collected during and after the spill. Assessment efforts for marine mammals have involved and will continue to involve a variety of surveillance and monitoring activities in the Gulf of Mexico, such as:
In October 2010 the Trustees confirmed damage and injury to natural resources as a result of the spill and issued a notice of intent to begin planning restoration activities. Planning and implementation of restoration activities likely will take several years and require integration and analysis of multiple types of information. These include measures and comparisons of the ecological, biological, geophysical, chemical, and oceanographic conditions in the Gulf, both pre- and post-spill, and/or modeling of conditions where pre- and/or post-spill information is not available.
Restoration activities that may benefit marine mammals include not only clean-up of the spilled oil, but also (1) basic assessment of the marine mammal stocks in the Gulf, and (2) reduction of other human-related risk factors in the Gulf, such as noise from seismic surveys, vessel traffic, sonar and military activities; fishery interactions; disturbance from tourism and illegal feeding; harmful algal blooms and anoxic zones.
Determining the respective roles of human-related risk factors and their interactions with the spill is a substantial but important challenge. In 2010, prior to the spill, unusually high numbers of bottlenose dolphins began to strand in the northern Gulf. Strandings continued to occur in high numbers throughout the spill and through spring and summer 2011. NOAA has declared these deaths to be an Unusual Mortality Event (in accordance with the Marine Mammal Protection Act), and is coordinating the investigation of these mortalities (pre- and post-oil spill) with ongoing Natural Resource Damage Assessment activities where the data needs of these two processes coincide.
Priorities for assessing the spillís long-term effects on Gulf marine mammals
Responding to stranded animals and assessment of immediate effects of oil are of the utmost priority during or immediately after a spill. However, the likelihood of detecting certain impacts decreases with time and the utility and value of certain types of research declines accordingly. Therefore, the Commission gives high priority at this time to assessment of long-term effects, including:
Implementation of the needed research will require resources beyond those currently available, as well as improved infrastructure (e.g., research vessels, aircraft, and laboratories), more trained personnel, better sampling methods, and refined analytical tools to detect and assess the effects of exposure to oil. Coordination of public and private research activities is critical to focus on the most important topics, achieve collaboration to the greatest degree possible, develop a weight-of-evidence approach for detecting effects, and avoid unnecessary duplication of effort. Collaboration and partnerships among the involved federal, state, and local agencies, industry, non-governmental organizations, research institutions and organizations, and the public also should help maximize the benefits of limited resources and minimize the effects of research activities on marine mammals.
Future research strategies and capacity
The extent to which we can learn more about the spill’s effects on marine mammals, as well as the effects of other human-related factors, will depend largely on our ability to improve research strategies and capacity in the Gulf. The Deepwater Horizon oil spill provided a sobering indicator of the shortcomings of our current research and management approach for marine mammals in the Gulf of Mexico. Those shortcomings can be grouped under five key topics, as follows:
Web Sites for Further Information
U.S. Government Web site on Gulf of Mexico oil spill response and restoration activities:
NOAA Office of Response and Restoration Web site on Deepwater Horizon Oil Spill Response:
NOAA Damage Assessment, Remediation, and Restoration Program’s Gulf Spill Restoration web site (including Natural Resource Damage Assessment work plans):
National Marine Fisheries Service Office of Protected Resources Gulf of Mexico oil spill web site:
U.S. Fish and Wildlife Service Web site on Deepwater Horizon Oil Spill Response:
Environmental Protection Agency Response to the BP Oil Spill in the Gulf of Mexico web site:
Oiled Wildlife Care Network Blog (includes archived postings regarding Deepwater Horizon response activities):
Bureau of Ocean Energy Management, Regulation and Enforcement BP/Deepwater Horizon oil spill library and reading room: http://www.boemre.gov/deepwaterreadingroom
National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling web site and report:
U.S. Coast Guard/Bureau of Ocean Energy Management, Regulation and Enforcement Joint Investigation Team web site and report: http://www.deepwaterinvestigation.com
Gulf of Mexico Research Initiative (BP funded research on effects of the Deepwater Horizon oil spill and related topics): http://www.gulfresearchinitiative.org
Gulf of Mexico Sea Grant Programs Deepwater Horizon Oil Spill Research and Monitoring Activities Database: http://gulfseagrant.tamu.edu/oilspill/database.htm
National Marine Fisheries Service Permits web site (whales and dolphins):
Fish and Wildlife Service Permits web site (manatees):