Pod of dolphins jumping and feeding in an orange oil slick during Deepwater Horizon oil spill (NOAA).

Oil Spill Assessment for Marine Mammals

NOAA Publishes New Guidelines Assessing Exposure and Impacts of Oil Spills on Marine Mammals

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Map Below: Current oil spill case locations from NOAA's Damage Assessment Remediation and Restoration Program (NOAA).

Map Above: Current oil spill case locations from NOAA's Damage Assessment Remediation and Restoration Program (NOAA).

Since thousands of oil spills of varying sizes occur in U.S. waters each year, oil spill scientists must be prepared to respond to and assess the impacts of oil on marine mammals.

To do this, the National Oceanic and Atmospheric Administration (NOAA) has published:

"Guidelines for Assessing Exposure and Impacts of Oil Spills on Marine Mammals"

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These guidelines provide a review of considerations for marine mammals under NOAA's jurisdiction, incorporating knowledge gained from previous oil spills, especially the 2010 Deepwater Horizon spill.

This story map is an overview of some of the information, tools, and figures found in the report.

Marine Mammal Biology

Marine mammals occupy most offshore and coastal American waters.

Some species occupy nearshore waters, others include mid or deep water as part of their range, while others spend part of their time resting on land or ice.

Killer whale stalks a seal on ice float (NOAA).

All marine mammals occupy the surface waters of oceans, as they breathe air at the surface. This puts them at risk of surfacing in or near floating oil slicks. 

Several different species of marine mammals may occupy the same area, so oil spills can impact multiple species of marine mammals. 

Marine Mammal Diet

With the exception of manatees, most marine mammals are predatory, feeding on plankton, fish, shellfish, small invertebrates and even other marine mammals.

Consuming oiled prey is one way marine mammals can be exposed to oil during a spill. Contaminated prey can also be a long-term danger of oil spills as contaminants move through the ecosystem. 

Baleen whale surfaces while feeding (NOAA).

Marine Mammal Lifecycles

All marine mammals give birth to live young one at a time, produce milk, and nurse their young. Seals and sea lions reach sexual maturity around 4-5 years of age, but it can take whales between 5-14 years before they become sexually mature.

This means that marine mammal populations are vulnerable to traumatic events. It can take populations a very long time to recover after a devastating event like an oil spill. 

Mother sea lion and her pup (NOAA).


Marine Mammal Vulnerability to Oil

Petroleum products are complex and contain many compounds that can harm marine mammals and can cause death, cancers, and organ damage. Some oil compounds can linger in the water for a long time and accumulate in the bodies of living things.

Three dolphins swimming just beneath oiled water.

Dolphins swimming through oiled water during the Deepwater Horizon oil spill (NOAA).

Marine Mammals Can Be Exposed to Oil In Several Ways

Dolphin with oiled skin during the Deepwater Horizon oil spill (NOAA).

Their bodies can be oiled by swimming through oiled water.

Oil can be inhaled and aspirated as they breathe at the surface.

Oil can be ingested by preening fur seals as they clean themselves.

Oil can be ingested by consuming oiled water or prey.  

Mammals break down oil in their bodies quickly, so it can be difficult to determine oil exposure through chemical analysis if much time has passed.

The Science of Oil Exposure

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Learning from Past Spills

What we know about impacts on marine mammals from oil we learned mostly from the 1989 Exxon Valdez oil spill in Alaska and the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. 

Deepwater Horizon provided very strong evidence supporting injury to cetaceans (especially dolphins) from oil.

Within 18 months of Exxon Valdez two pods of killer whales experienced unprecedented number of deaths, ranging from 30%-40% mortality.

Decades later, neither pod has fully recovered.

Other whales died in record numbers in the six months following Exxon Valdez, -37 carcasses of cetaceans were found, although it was impossible to link oil to these casualties. 

Injuries to Dolphins from Deepwater Horizon

The Deepwater Horizon oil spill also provided strong evidence linking oil exposure to harm in marine mammals.

Common bottlenose dolphins from areas polluted with DWH oil suffered from lung disease, adrenal disease, poor body conditions, and other problems linked to oil exposure. 

More than 80% of the bottlenose dolphin pregnancies failed in the most polluted areas in the years following Deepwater Horizon. 

How Oil Causes Injury

Petroleum products are complex and contain many compounds that can harm marine mammals.

The most harmful compounds, single ringed, are found during and just after a spill. They are responsible for sudden deaths of animals, and can cause cancers and organ damage. 

Polycyclic Aromatic Hydrocarbons (PAHs) are another harmful compund linked to cancers, infertility, and immune system damage.

Some PAHS can linger in the water and accumulate in living things, causing health and reproductive problems that may be passed down to future generations. 

Impacts of Response Actions

Response actions, including the physical removal of oil from the environment through skimming, or burning, can harm marine mammals. 

Support and response vessel activity, shoreline oil assessments, or booming to contain oil can also cause accidental boat strikes. This document aims to inform responders about risks to marine mammals and guide best practices for oil spill response.

Oil Spill Emergency Response

When spills occur, NOAA provides scientific information to the Unified Command, which coordinates Incident Commanders from all organizations involved in oil sill response. 

NOAA may conduct shoreline assessments, aerial overflights and trajectory modeling to identify resources at risk. These activities are critical to guiding decision making by the Unified Command. 

Surveying the shore during Deepwater Horizon (NOAA).

Stranding Networks

During an oil spill where marine mammals may be affected, NOAA and stranding networks will participate in the the response to rescue and rehabilitate live animals and study dead animals in the spill area.

There are currently 32 facilities that can rehabilitate stranded marine mammals under NOAA's jurisdiction. In total, there are over 120 organizations or stranding network participants who are authorized to respond to marine mammal strandings.

Dead dolphin washed ashore in Barataria Bay after Deepwater Horizon (NOAA).

Map to Right: Oil footprint of Deepwater Horizon on 5/1/2010 and trajectory estimate of beached oil.

Understanding where oil is, where it is going, and what resources it might impact, is critical to mobilizing stranding networks.

How Stranding Networks Work

Oil spills are not the only reason a marine mammal may become stranded. Other possible causes include disease, parasites, harmful algal blooms, ship strikes, entanglement and weather events.

Some stranding network participants only respond to marine mammals on the beach, lacking facilities for rehabilitation. Other participants do engage in rescue and rehabilitation.

These participants may include Federal, state, and local government entities, non-governmental organizations, academic institutions, museums, and scientists among others.

Seal pup recovered after Exxon Valdez (Alaska Public Archives).

Methods for Assessing Injury to Marine Mammals from Oil Spills

No two oil spills are the same, so it is important for oil spill responders and marine mammal experts to be familiar with methods for assessing injury to marine mammals before disaster strikes.

The methods described in the Slideshow below represent the best starting points when planning a marine mammal oil spill assessment, although there may be other approaches appropriate for specific regions, species, and scenarios.

All field methods that involve approaching, handling, or sampling marine mammals (live or dead) require permits under the Marine Mammal Protection Act and Endangered Species Act.

Gray seal tagging for a research project in Massachusetts (NOAA).

Assessment Methods

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Photo Documentation

Collecting photos or videos of marine mammals in or near oil is the most common way to collect data for Natural Resource Damage Assessments. 

High quality and geo-referenced photos of dead animals, animals with oil on them, swimming in oil, or interacting with response operations are powerful evidence for a case.

Capture-Release Health Assessment

Hands-on sampling of animals can be conducted for a limited group of seals, sea lions, and small dolphins and porpoises.

Researchers can conduct a physical examination, ultrasound, collect blood or tissue samples, and mark individuals through tags or branding. 

This allows for follow-up on individual animals for long-term injuries.

Information from these studies can be very important for documenting injury from oil spills.

Sampling of Oil

Measuring the amount of oil in the water, sediments, air or prey is an indicator of exposure that supports injury to marine mammals.

Documenting the geographic extent of oil spills allows scientists to identify overlap with places marine mammals are known to live. 

Gathering this information is also important to link the specific type of oil spilled to contaminats found in sick or injured marine mammals. 

Map: PAH detects for all Deepwater Horizon water samples on 06/12/2010 (NOAA)

Visual Health Assessment 

Visual health assessment techniques may be appropriate for some species, particularity for large animals where capture-release is not possible.

Experts collect and review photographs to evaluate skin condition, scarring, presence of calves, and body condition. 

Visual health assessments have been preformed for several species of whales and leopard seals in oil spills. 

Sampling of Feces

Fecal samples have long been studied for information specific to digestive health and diet analysis, and have also been shown to contain hormones that indicate stress. 

Feces and vomit (spew) can be collected from the surface where a group of seals or sea lions has been resting, or from the water for samples that float.

Fecal samples from large whales can be encountered opportunistically, or by using trained dogs. 

Sampling of Breath

Whales and dolphins are surface breathers who inhale large amounts of air and exhale clouds of "blow".

Scientists collect samples using poles or drones, then test for hormones, microbes, and other factors to determine the animal's immune function. 

Currently remote breath sampling is only useful for large whales, but breath can also be sampled in smaller cetaceans during capture-release assessments.

Necropsy

A significgant amount of information can be gathered from a recently deceased stranded marine mammal, for example data on disease and parasites, reproductive biology, life history and exposure to pollution. 

As a carcass degrades the amount of usable information that can be gathered is reduced, so it is important to perform necropsies as quickly as possible. 

Passive Acoustic Monitoring

Marine mammals, especially whales and dolphins, produce underwater sounds. Passive acoustic monitoring surveys marine mammals that are easier to hear than to see. 

Scientists deploy microphones to collect and detect marine mammals in the environment. 

This method can be used to confirm the presence of animals in the area of a spill.

It can also be used to monitor shifts in distribution or declines of abundance, inferring loss of individuals due to injury. 

Remote Biopsy

Remote biopsy collection is a technique used to collect skin and blubber samples using a pneumatic rifle, pole spear, or crossbow. 

Darts collect and hold the sample until it can be collected for processing. 

Remote Biopsy (Cont.)

​This method allows for a sample to be collected form a free-swimming animal with minimal disturbance. 

The sample can provide a wealth of information, including genetic information, stable isotope analysis, and hormone concentrations. 

However, more research is needed on tracing oil-derived contaminants in blubber. 

Using Sound Science to Hold Polluters Accountable

America's marine resources are public resources, they belong to us all.

The assessment methods outlined above are best practices to collect quality data after oil spills, hazardous waste spills and ship groundings, allowing NOAA and our partners to hold responsible parties accountable for injuries to marine mammals and fund restoration on behalf of all Americans.

NOAA Damage Assessment Remediation and Restoration Program oil spill, hazardous waste, and ship grounding site locations (NOAA).

Laws for Marine Mammals & Oil Spills

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Marine Mammal Protection Act

The primary objective of the Marine Mammal Protection Act (MMPA) is to maintain the health and stability of marine ecosystems and the marine mammals that inhabit them.

The MMPA established a national policy to prevent marine mammal species from declining beyond a the point they are not functioning elements of their ecosystems. 

All marine mammal species (live and dead animals) regardless of their population status, are protected under the MMPA. 

Oil Pollution Act

The Oil Pollution Act (OPA) was enacted in 1990. It strengthened the Nation's ability to prevent and respond to oil spills after Exxon Valdez.

If an oil spill occurs in an area where marine mammals are known to be, NOAA works with the U.S Fish and Wildlife Service Ecological Services to coordinate wildlife response. 

Endangered Species Act

The Endangered Species Act (ESA) protects species that are endangered or threatened with extinction, and the conservation of their critical habitats.

During an oil spill, many of the efforts to rescue marine mammals and clean up their habitats fall under ESA definitions of "take".

There are emergency protocols within ESA to best help endangered species in oil spills. Emergency Section 7 consultation is engaged in these cases.

National Marine Sanctuaries Act

This act protects marine and coastal environments that are of special national significance, regulating harmful activities within sanctuaries.

NOAA-Office of Marine Sanctuaries assists in response actives to minimize harm within sanctuaries. 

Guidelines for Assessing Exposure and Impacts of Oil Spills on Marine Mammals

    Included in this publication are tools and information about marine mammals to help prepare for future disasters. Although the needs of each oil spill are unique, these guidelines serve as a planning tool to use sound science to prepare for future spills.

Experts at NOAA continue to work diligently with our partners, so when oil spill disasters strike we will be even better prepared to respond on behalf of marine mammals.

Mother sea lion and pup (NOAA).

For More Information Please Visit:

Or Contact

  • Laurie Sullivan: laurie.sullivan@noaa.gov
  • Tom Brosnan: tom.brosnan@noaa.gov
  • Megan Ewald: megan.ewald@noaa.gov

All Images Are Credited to NOAA and Are in the Public Domain

 

Dolphins swimming through oiled water during the Deepwater Horizon oil spill (NOAA).

Dolphin with oiled skin during the Deepwater Horizon oil spill (NOAA).

Gray seal tagging for a research project in Massachusetts (NOAA).

Mother sea lion and pup (NOAA).

Killer whale stalks a seal on ice float (NOAA).

Baleen whale surfaces while feeding (NOAA).

Mother sea lion and her pup (NOAA).

Surveying the shore during Deepwater Horizon (NOAA).

Dead dolphin washed ashore in Barataria Bay after Deepwater Horizon (NOAA).

Seal pup recovered after Exxon Valdez (Alaska Public Archives).