NOAA's Response and Restoration Blog

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Latest NOAA Study Ties Deepwater Horizon Oil Spill to Spike in Gulf Dolphin Deaths

Group of dolphin fins at ocean surface.

A study published in the journal PLOS ONE found that an unusually high number of dead Gulf dolphins had what are normally rare lesions on their lungs and hormone-producing adrenal glands, which are associated with exposure to oil compounds. (NOAA)

What has been causing the alarming increase in dead bottlenose dolphins along the northern Gulf of Mexico since the Deepwater Horizon oil spill in the summer of 2010? Independent and government scientists have found even more evidence connecting these deaths to the same signs of illness found in animals exposed to petroleum products, as reported in the peer-reviewed online journal PLOS ONE.

This latest study uncovered that an unusually high number of dead Gulf dolphins had what are normally rare lesions on their lungs and hormone-producing adrenal glands.

The timing, location, and nature of the lesions support that oil compounds from the Deepwater Horizon oil spill caused these lesions and contributed to the high numbers of dolphin deaths within this oil spill’s footprint.

“This is the latest in a series of peer-reviewed scientific studies, conducted over the five years since the spill, looking at possible reasons for the historically high number of dolphin deaths that have occurred within the footprint of the Deepwater Horizon spill,” said Dr. Teri Rowles, one of 22 contributing authors on the paper, and head of NOAA’s Marine Mammal Health and Stranding Response Program, which is charged with determining the causes of unusual mortality events.

“These studies have increasingly pointed to the presence of petroleum hydrocarbons as being the most significant cause of the illnesses and deaths plaguing the Gulf’s dolphin population,” said Dr. Rowles.

A System out of Balance

In this study, one in every three dead dolphins examined across Louisiana, Mississippi and Alabama had lesions affecting their adrenal glands, resulting in a serious condition known as “adrenal insufficiency.” The adrenal gland produces hormones—such as cortisol and aldosterone—that regulate metabolism, blood pressure and other bodily functions.

“Animals with adrenal insufficiency are less able to cope with additional stressors in their everyday lives,” said Dr. Stephanie Venn-Watson, the study’s lead author and veterinary epidemiologist at the National Marine Mammal Foundation, “and when those stressors occur, they are more likely to die.”

Earlier studies of Gulf dolphins in areas heavily affected by the Deepwater Horizon oil spill found initial signs of this illness in a 2011 health assessment of dolphins living in Barataria Bay, Louisiana. NOAA scientists Dr. Rowles and Dr. Lori Schwacke spoke about the results of this health assessment in a 2013 interview:

“One rather unusual condition that we noted in many of the Barataria Bay dolphins was that they had very low levels of some hormones (specifically, cortisol) that are produced by the adrenal gland and are important for a normal stress response.

Under a stressful condition, such as being chased by a predator, the adrenal gland produces cortisol, which then triggers a number of physiological responses including an increased heart rate and increased blood sugar. This gives an animal the energy burst that it needs to respond appropriately.

In the Barataria Bay dolphins, cortisol levels were unusually low. The concern is that their adrenal glands were incapable of producing appropriate levels of cortisol, and this could ultimately lead to a number of complications and in some situations even death.”

Swimming with Pneumonia

Ultrasounds showing a normal dolphin lung, compared to lungs with mild, moderate, and severe lung disease.

Ultrasounds showing a normal dolphin lung, compared to lungs with mild, moderate, and severe lung disease. These conditions are consistent with exposure to oil compounds and were found in bottlenose dolphins living in Barataria Bay, Louisiana, one of the most heavily oiled areas during the Deepwater Horizon oil spill. (NOAA)

In addition to the lesions on adrenal glands, the scientific team discovered that more than one in five dolphins that died within the Deepwater Horizon oil spill footprint had a primary bacterial pneumonia. Many of these cases were unusual in severity, and caused or contributed to death.

Drs. Rowles and Schwacke previously had observed significant problems in the lungs of dolphins living in Barataria Bay. Again, in 2013, they had noted, “In some of the animals, the lung disease was so severe that we considered it life-threatening for that individual.”

In other mammals, exposure to petroleum-based polycyclic aromatic hydrocarbons, known as PAHs, through inhalation or aspiration of oil products can lead to injured lungs and altered immune function, both of which can increase an animal’s susceptibility to primary bacterial pneumonia. Dolphins are particularly susceptible to inhalation effects due to their large lungs, deep breaths, and extended breath hold times.

Learn more about NOAA research documenting the impacts from the Deepwater Horizon oil spill and find more stories reflecting on the five years since this oil spill.


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NOAA Launches New Data Management Tool for Public Access to Deepwater Horizon Oil Spill Data

Two people launch a water column sampling device off the side of a ship.

Launching a device to take measurements in the water column during the 2010 Deepwater Horizon oil spill. NOAA built the online tool DIVER to organize and provide access to these scientific data and the many others collected in the wake of the spill. (NOAA)

A flexible new data management tool—known as DIVER and developed by NOAA to support the Natural Resource Damage Assessment (NRDA) for the 2010 Deepwater Horizon oil spill—is now available for public use. DIVER stands for “Data Integration, Visualization, Exploration and Reporting,” and it can be accessed at https://dwhdiver.orr.noaa.gov.

DIVER was developed as a digital data warehouse during the Deepwater Horizon oil spill response effort and related damage assessment process, which has required collecting and organizing massive amounts of scientific data on the environmental impacts of the spill.

The tool serves as a centralized data repository that integrates diverse environmental data sets collected from across the Gulf of Mexico ecosystem. It allows scientists from different organizations and laboratories located across the country to upload field data, analyses, photographs, and other key information related to their studies in a standardized format. DIVER thus brings together all of that validated information into a single, web-based tool.

In addition, DIVER provides unprecedented flexibility for filtering and downloading validated data collected as part of the ongoing damage assessment efforts for the Gulf of Mexico. The custom query and mapping interface of the tool, “DIVER Explorer,” provides both a data filter and review tools, which allow users to refine how they look for data and explore large data sets online. Query results are presented in an interactive dashboard, with a map, charts, table of results, metadata (data about the data), and sophisticated options for exporting the data.

View of DIVER Explorer map and query results for environmental impact data in the Gulf of Mexico.

A view of DIVER Explorer query results shown in an interactive dashboard. (NOAA)

In addition to the DIVER Explorer query tools, this website presents a detailed explanation of our data management approach, an explanation of field definitions and codes used in the data warehouse, and a robust help section.

Currently, DIVER provides access to nearly 4 million validated results of analytical chemistry from over 50,000 samples of water, tissue, oil, and sediment collected by federal, state, academic, and nongovernmental organizations to support the Deepwater Horizon damage assessment. As additional data sets become publicly available they will be accessible through the DIVER Explorer tool.

Read the announcement of this tool’s public launch from the NOAA website.


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NOAA Builds Tool to Hold Unprecedented Amounts of Data from Studying an Unprecedented Oil Spill

This is a post by Benjamin Shorr of NOAA’s Office of Response and Restoration.

The Deepwater Horizon Oil Spill: Five Years Later

This is the seventh in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

The Deepwater Horizon oil spill was the largest marine oil spill in U.S. history. In the wake of this massive pollution release, NOAA and other federal and state government scientists need to determine how much this spill and ensuing response efforts harmed the Gulf of Mexico’s natural resources, and define the necessary type and amount of restoration.

That means planning a lot of scientific studies and collecting a lot of data on the spill’s impacts, an effort beginning within hours of the spill and continuing to this day.

Scientists collected oil samples from across the Gulf Coast. Oil spill observers snapped photographs of oil on the ocean surface from airplanes. Oceanographic sensors detected oil in the water column near the Macondo wellhead. Biologists followed the tracks of tagged dolphins as they swam through the Gulf’s bays and estuaries. Scientists are using this type of information—and much more—to better understand and assess the impacts to the Gulf ecosystem and people’s uses of it.

But what is the best way to gather together and organize what would become an unprecedented amount of data for this ongoing Natural Resource Damage Assessment process? Scientists from across disciplines, agencies, and the country needed to be able to upload their own data and download others’ data, in addition to searching and sorting through what would eventually amount to tens of thousands of samples and millions of results and observations.

First, a Quick Fix

Early on, it became clear that the people assessing the spill’s environmental impacts needed a single online location to organize the quickly accumulating data. To address this need, a team of data management experts within NOAA began creating a secure, web-based data repository.

This new tool would allow scientific teams from different organizations to easily upload their field data and other key information related to their studies, such as scanned field notes, electronic data sheets, sampling protocols, scanned images, photographs, and navigation information. Graphic with gloved hands pouring liquid from sample jar into beaker and numbers of samples, results, and studies resulting from NOAA efforts. While this data repository was being set up, NOAA needed an interim solution and turned to its existing database tool known as Query Manager. Query Manager allowed users to sort and filter some of the data types being collected for the damage assessment—including sediment, tissue, water, and oil chemistry results, as well as sediment and water toxicity data—but the scope and scale of the Deepwater Horizon oil spill called for more flexibility and features in a data management tool. When NOAA’s new data repository was ready, it took over from Query Manager.

Next, a New Data Management Solution

As efforts to both curtail and measure the spill’s impacts continued, the amount and diversity of scientific data began pouring in at unprecedented rates. The NOAA team working on the new repository took stock of the types of data being entered into it and realized a database alone would not be enough. They searched for a better way to not only manage information in the repository but to organize the data and make them accessible to myriad scientists on the Gulf Coast and in laboratories and offices across the country.

Building on industry standard, open source tools for managing “big data,” NOAA developed a flexible data management tool—known as a “data warehouse”—which gives users two key features. First, it allows them to integrate data sets and documents as different as oceanographic sensor data and field observations, and second, it allows users to filter and download data for further analysis and research.

Now, this data warehouse is a little different than the type of physical warehouse where you stack boxes of stuff on row after row of shelves in a giant building. Instead, this web-based warehouse contains a flexible set of tables which can hold various types of data, each in a specific format, such as text documents in .pdf format or images in .jpg format.

Screenshot of data management tool showing map with locations of various data.

NOAA’s data management tool allows users to integrate very different data sets and documents, such as water and oil samples and field observations, as well as filter and download data for further analysis and research. (NOAA)

To fill this digital warehouse with data, the development team worked with the scientific and technical experts, who in many cases were out collecting data in places impacted by the oil spill, to establish a flow of information into the appropriate tables in the warehouse. In addition, they standardized formats for entering certain data, such as date, types of analysis, and names of species.

Manual and automated checks ensure the integrity of the data being entered, a process which gets easier as new data arrive in the warehouse and are incorporated into the proper table. The process of standardizing and integrating data in one accessible location also helps connect cross-discipline teams of scientists who may be working on different parts of the ecosystem, say marsh versus nearshore waters.

The NOAA team has also created a custom-built “query tool” for the data warehouse that can search and filter all of those diverse data in a variety of ways. A user can filter data by one or more values (such as what type of analysis was done), draw a box around a specific geographic area to search and filter data by location, select a month and year to sort by date sampled, or even type in a single keyword or sample ID. This feature is critical for the scientists and technical teams tasked with synthesizing data across time and space to uncover patterns of environmental impact.

Download the Data Yourself

NOAA’s data warehouse currently holds validated damage assessment data from more than 53,000 water, tissue, oil, and sediment samples, which, once these samples were analyzed, have led to over 3.8 million analytical results, also stored within the new tool. Together, NOAA’s samples and analytical results have informed more than 16 scientific studies published in peer-reviewed scientific journals, as well as many other academic and scientific publications.

While not all of the data from the damage assessment are publicly available yet, you can access validated data collected through cooperative studies or otherwise made available through the Natural Resource Damage Assessment legal process.

You can find validated data exported from NOAA’s digital data warehouse available for download on both the Natural Resource Damage Assessment website and NOAA’s interactive online mapping tool for this spill, the ERMA Deepwater Gulf Response website. Stay tuned for more about this new tool, including additional details on how it works and where you can find it.


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Who Is Funding Research and Restoration in the Gulf of Mexico After the Deepwater Horizon Oil Spill?

This is a post by Kate Clark, Acting Chief of Staff with NOAA’s Office of Response and Restoration, and Frank Parker, Associate Director for the NOAA RESTORE Act Science Program, with NOAA’s National Centers for Coastal Ocean Science.

The Deepwater Horizon Oil Spill: Five Years Later

This is the fourth in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

When an oil spill takes place, people want to see the coasts, fish, wildlife, and recreational opportunities affected by that spill restored—so they can be as they were before, as quickly as possible. Fortunately, the Oil Pollution Act of 1990 supports this. After most major oil spills, what routinely happens is the government undertakes a Natural Resource Damage Assessment, a rigorous, scientific process of assessing environmental injuries and, with public input, identifying and implementing the appropriate amount of restoration to compensate for the injuries resulting from this spill (all paid for by those responsible for the pollution).

What is not routine in the wake of an oil spill is the groundswell of support for even more research and restoration, beyond the scope of the usual damage assessment process, to bolster the resilience of the impacted ecosystem and coastal communities. Yet that is exactly what happened after the Deepwater Horizon well blowout in 2010, which renewed a national interest in the unique environment that is the Gulf of Mexico.

In the wake of this disaster, there have been various additional investments, outside of the Natural Resource Damage Assessment process, in more broadly learning about and restoring the Gulf of Mexico. These distinct efforts to fund research and restoration in the Gulf have been sizable, but keeping track of them can be, frankly, a bit confusing.

The many organizations involved are working to ensure the Gulf’s new infusions of funding for restoration and research are well coordinated. However, keep in mind that each effort is independent of the others in funding mechanism, primary mandate, and process.

Tracking Dollars for Gulf Restoration

In one effort, announced while the Macondo well was still gushing oil, BP dedicated up to $500 million dollars to be spent over 10 years “to fund an independent research program designed to study the impact of the oil spill and its associated response on the environment and public health in the Gulf of Mexico.” This investment spawned the Gulf of Mexico Research Initiative, or GOMRI, which is governed by an independent, academic research board of 20 science, public health, and research administration experts and independent of BP’s influence.

Meanwhile, BP faced both potential criminal and civil penalties under the Clean Water Act, which regulates the discharge of pollutants into U.S. waters. When such penalties are pursued by the government for pollution events, such as an oil spill, a portion of the criminal monetary penalties are usually paid to a local environmental foundation or conservation organization to administer the funds.

Ultimately, BP agreed to a $4 billion criminal settlement in 2013, with the bulk of that money going to North American Wetlands Conservation Fund, National Fish and Wildlife Foundation, and National Academy of Sciences.

Chart showing various investments and their recipients for science and restoration efforts in the Gulf of Mexico after the Deepwater Horizon oil spill.

Science and restoration initiatives in the Gulf of Mexico following the Deepwater Horizon oil spill. (NOAA)

That still leaves civil penalties to be determined. Normally, civil penalties under the Clean Water Act are directed to the General Treasury.

However, Congress passed legislation calling for 80 percent of the administrative and civil penalties related to the Deepwater Horizon oil spill to be diverted directly to the Gulf of Mexico for ecological and economic restoration. This legislation, known as the RESTORE Act (Resources and Ecosystems Sustainability, Tourist Opportunities, and Revived Economies of the Gulf Coast States Act of 2012), passed on July 6, 2012.

While the full extent of BP’s civil penalties have yet to be determined, in 2013 the Department of Justice finalized a civil settlement with Transocean in the amount of $1 billion. This settlement results in more than $800 million going to the Gulf of Mexico under the RESTORE Act. As to penalties for BP, the court has currently ruled on two of the three trial phases. Based on those rulings, currently under appeal, the penalty cap for BP is $13.7 billion. A third trial phase for factors that are taken into account in establishing the penalty at or under that cap was concluded in February 2015. The court has yet to rule on the third phase of the trial, and the pending appeals have not yet been heard by the appeals court.

NOAA and Restoration in the Gulf

So where does NOAA fit into all of this? NOAA is carrying out its usual duties of working with its partners to assess injury to and restore impacted natural resources through the Natural Resource Damage Assessment process. However, NOAA also is involved in supporting broader Gulf research and resilience, which will complement the damage assessment process, in two new ways through the RESTORE Act.

First, NOAA is supporting in the RESTORE Act’s Gulf Coast Ecosystem Restoration Council, which is chaired by Commerce Secretary Penny Pritzker (NOAA sits in the Department of Commerce). Second, NOAA is leading the Gulf Coast Ecosystem Restoration Science, Observation, Monitoring, and Technology Program, or more simply, the NOAA RESTORE Act Science Program.

A NOAA ship at dock.

NOAA is leading a science program aimed at improving our understanding of the Gulf of Mexico and the plants and animals that live there, in order to better protect and preserve them. (NOAA)

This program exists because we simply don’t know as much as we need to know about the Gulf of Mexico and the plants and animals that live there in order to reverse the general decline of coastal ecosystems and ensure resilience in the future.

To make sure this new science program addresses the needs of the region, NOAA, in partnership with the U.S. Fish and Wildlife Service, met with resource managers, scientists, and other Gulf of Mexico stakeholders to discuss what the focus of the program should be. We heard three key messages loud and clear:

  • Make sure the research we support is closely linked to regional resource management needs.
  • Coordinate with other science initiatives working in the region.
  • Make the results of research available quickly to those who could use them.
Woman checks for bubbles in a sample of water on board the NOAA Ship Pisces.

The NOAA RESTORE Act Science Program is already in the process of making available $2.5 million for research in the Gulf of Mexico, with more opportunities to come. (NOAA)

NOAA and the U.S. Fish and Wildlife Service have designed a science plan [PDF] for the NOAA RESTORE Act Science Program that outlines how we will make this happen.

The science plan describes the research priorities highlighted during our engagement with stakeholders and from reviewing earlier assessments of the science needed to better understand the Gulf of Mexico. These priorities will guide how the program directs its funding over the coming years.

The research priorities include improving our understanding of how much and when freshwater, sediment, and nutrients enter the coastal waters of the Gulf of Mexico and what this means for the growth of wetlands and the number of shellfish and fish in the Gulf of Mexico. Another priority is developing new techniques and technologies for measuring conditions in the Gulf to help inform resource management decisions.

Apply for Research Funding

Currently, the NOAA RESTORE Act Science Program is holding its first competition for funding, with over 100 research teams already responding. It will make $2.5 million available for researchers to review and integrate what we already know about the Gulf of Mexico and work with resource managers to develop strategies directing the program toward our ultimate goal of supporting the sustainability of the Gulf and its fisheries.

The results of this work also will help inform the direction of other science initiatives and restoration activities in the Gulf region. NOAA and the U.S. Fish and Wildlife Service will announce the winners of this funding competition in the fall of 2015.

To learn more about the NOAA RESTORE Act Science Program and future funding opportunities, visit http://restoreactscienceprogram.noaa.gov/.


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In the Wake of the Deepwater Horizon Oil Spill, Gulf Dolphins Found Sick and Dying in Larger Numbers Than Ever Before

The Deepwater Horizon Oil Spill: Five Years Later

This is the third in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

A dolphin is observed with oil on its skin on August 5, 2010, in Barataria Bay, La.

A dolphin is observed with oil on its skin on August 5, 2010, in Barataria Bay, Louisiana. (Louisiana Department of Wildlife and Fisheries/Mandy Tumlin)

Dolphins washing up dead in the northern Gulf of Mexico are not an uncommon phenomenon. What has been uncommon, however, is how many more dead bottlenose dolphins have been observed in coastal waters affected by the Deepwater Horizon oil spill in the five years since. In addition to these alarmingly high numbers, researchers have found that bottlenose dolphins living in those areas are in poor health, plagued by chronic lung disease and failed pregnancies.

Independent and government scientists have undertaken a number of studies to understand how this oil spill may have affected dolphins, observed swimming through oil and with oil on their skin, living in waters along the Gulf Coast. These ongoing efforts have included examining and analyzing dead dolphins stranded on beaches, using photography to monitor living populations, and performing comprehensive health examinations on live dolphins in areas both affected and unaffected by Deepwater Horizon oil.

The results of these rigorous studies, which recently have been and continue to be published in peer-reviewed scientific journals, show that, in the wake of the 2010 Deepwater Horizon oil spill and in the areas hardest hit, the dolphin populations of the northern Gulf of Mexico have been in crisis.

Troubled Waters

Due south of New Orleans, Louisiana, and northwest of the Macondo oil well that gushed millions of barrels of oil for 87 days, lies Barataria Bay. Its boundaries are a complex tangle of inlets and islands, part of the marshy delta where the Mississippi River meets the Gulf of Mexico and year-round home to a group of bottlenose dolphins.

During the Deepwater Horizon oil spill, this area was one of the most heavily oiled along the coast. Beginning the summer after the spill, record numbers of dolphins started stranding, or coming ashore, often dead, in Barataria Bay (Venn-Watson et al. 2015). One period of extremely high numbers of dolphin deaths in Barataria Bay, part of the ongoing, largest and longest-lasting dolphin die-off recorded in the Gulf of Mexico, persisted from August 2010 until December 2011.

In the summer of 2011, researchers also measured the health of dolphins living in Barataria Bay, comparing them with dolphins in Sarasota Bay, Florida, an area untouched by the Deepwater Horizon oil spill. Differences between the two populations were stark. Many Barataria Bay dolphins were in very poor health, some of them significantly underweight and five times more likely to have moderate-to-severe lung disease. Notably, the dolphins of Barataria Bay also were suffering from disturbingly low levels of key stress hormones which could prevent their bodies from responding appropriately to stressful situations. (Schwacke et al. 2014)

“The magnitude of the health effects that we saw was surprising,” said NOAA scientist Dr. Lori Schwacke, who helped lead this study. “We’ve done these health assessments in a number of locations across the southeast U.S. coast and we’ve never seen animals that were in this poor of condition.”

The types of illnesses observed in live Barataria Bay dolphins, which had sufficient opportunities to inhale or ingest oil following the 2010 spill, match those found in people and other animals also exposed to oil. In addition, the levels of other pollutants, such as DDT and PCBs, which previously have been linked to adverse health effects in marine mammals, were much lower in Barataria Bay dolphins than those from the west coast of Florida.

Dead in the Water

Based on findings from the 2011 study, the outlook for dolphins living in one of the most heavily oiled areas of the Gulf was grim. Nearly 20 percent of the Barataria Bay dolphins examined that year were not expected to live, and in fact, the carcass of one of them was found dead less than six months later (Schwacke et al. 2014). Scientists have continued to monitor the dolphins of Barataria Bay to document their health, survival, and success giving birth.

Considering these health conditions, it should come as little surprise that record high numbers of dolphins have been dying along the coasts of Louisiana (especially Barataria Bay), Alabama, and Mississippi. This ongoing, higher-than-usual marine mammal die-off, known as an unusual mortality event, has lasted over four years and claimed more than a thousand marine mammals, mostly bottlenose dolphins. For comparison, the next longest lasting Gulf die-off (in 2005–2006) ended after roughly a year and a half (Litz et al. 2014 [PDF]).

Researchers studying this exceptionally long unusual mortality event, which began in February 2010, identified within it multiple distinct groupings of dolphin deaths. All but one of them occurred after the Deepwater Horizon oil spill, which released oil from April to July 2010, and corresponded with areas exposed heavily to the oil, particularly Barataria Bay (Venn-Watson et al. 2015). In early 2011, the spring following the oil spill, Mississippi and Alabama saw a marked increase in dead dolphin calves, which either died late in pregnancy or soon after birth, and which would have been exposed to oil as they were developing.

The Gulf coasts of Florida and Texas, which received comparatively little oiling from the Deepwater Horizon spill, did not see the same significant annual increases in dead dolphins as the other Gulf states (Venn-Watson et al. 2015). For example, Louisiana sees an average of 20 dead whales and dolphins wash up each year, but in 2011 alone, this state recorded 163 (Litz et al. 2014 [PDF]).

The one grouping of dolphin deaths starting before the spill, from March to May 2010, took place in Louisiana’s Lake Pontchartrain (a brackish lagoon) and western Mississippi. Researchers observed both low salinity levels in this lake and tell-tale skin lesions thought to be associated with low salinity levels on this group of dolphins. This combined evidence supports that short-term, freshwater exposure in addition to cold weather early in 2010 may have been key contributors to those dolphin deaths prior to the Deepwater Horizon spill.

Legacy of a Spill?

A bottlenose dolphin swims in the shallow waters along a sandy beach with orange oil boom.

A bottlenose dolphin swims in the shallow waters along the beach in Grand Isle, Louisiana, near oil containment boom that was deployed on May 28, 2010. Oil from the Deepwater Horizon oil spill began washing up on beaches here one month after the drilling unit exploded. (U.S. Coast Guard)

In the past, large dolphin die-offs in the Gulf of Mexico could usually be tied to short-lived, discrete events, such as morbillivirus and marine biotoxins (resulting from harmful algal blooms). While studies are ongoing, the current evidence does not support that these past causes are responsible for the current increases in dolphin deaths in the northern Gulf since 2010 (Litz et al. 2014).

However, the Deepwater Horizon oil spill—its timing, location, and nature—offers the strongest evidence for explaining why so many dolphins have been sick and dying in the Gulf since 2010. Ongoing studies are assessing disease among dolphins that have died and potential changes in dolphin health over the years since the spill.

As is the case for deep-sea corals, the full effects of this oil spill on the long-lived and slow-to-mature bottlenose dolphins and other dolphins and whales in the Gulf may not appear for years. Find more information related to dolphin health in the Gulf of Mexico on NOAA’s Unusual Mortality Event and Gulf Spill Restoration websites.


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At the Bottom of the Gulf of Mexico, Corals and Diversity Suffered After Deepwater Horizon Oil Spill

The Deepwater Horizon Oil Spill: Five Years Later

This is the second in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

Very little, if any, light from the sun successfully travels to the extreme bottom of the Gulf of Mexico. At these dark depths, the water is cold and the inescapable pressure of thousands of feet of ocean bears down on everything.

Yet life in the deep ocean is incredibly diverse. Here, delicate branches of soft coral are embraced by the curling arms of brittlestars. Slender sea fans, tinged with pink, reach for tiny morsels of food drifting down like snow from above. From minute marine worms to elongated fish, the diversity of the deep ocean is also a hallmark of its health and stability.

However, this picture of health was disrupted on April 20, 2010. Beginning that day and for almost three months after, the Macondo wellhead unleashed an unprecedented amount of oil and natural gas nearly a mile beneath the ocean. In addition, the response to this oil spill released large amounts of chemical dispersant, both at the source of the leaking oil and on the ocean surface. These actions were meant to break down oil that might have threatened life at the sea surface and on Gulf shores. Nevertheless, the implications for the ocean floor were largely unknown at the time.

In the five years since the Deepwater Horizon oil spill, a number of academic and independent scientists along with state and federal agencies, including NOAA and the Bureau of Ocean Energy Management, have been collaborating to study just how this oil spill and response affected the deep ocean and seafloor of the Gulf. What they found was the footprint of the oil spill on the seafloor, stamped on sickened deep-sea corals and out-of-balance communities of tiny marine invertebrates.

A Sickened Seafloor

A part of the world difficult to reach—and therefore difficult to know—the depths of the Gulf of Mexico required a huge collaborative and technological effort to study its inhabitants. Beginning in the fall of 2010, teams of scientists set out on multiple research cruises to collect deep-sea data, armed with specialized equipment, including remotely operated vehicles (ROVs), cameras capable of withstanding the crushing pressure of the deep ocean, and devices that could bore into the ocean bottom and scoop up multiple samples of sediments at a time.

Through these efforts, researchers have uncovered large areas of the Gulf of Mexico seafloor that contain most of the oil spill’s notable deep-sea impacts. One area in particular surrounds the damaged wellhead and stretches to the southwest, following the path of the massive underwater plume of Deepwater Horizon oil. At times, up to 650 feet thick and over a mile wide, the oil plume drifted at depths more than 3,500 feet beneath the ocean surface, leaving traces of its presence on the bottom as it went (Camilli et al. 2010).

The Macondo wellhead sits at the center of a bull’s-eye–shaped pattern of harm on the seafloor, with oil-related impacts lessening in intensity farther from the oil’s source. Further tying this pattern of injury to the Deepwater Horizon spill, a conservative chemical tracer of petroleum turned up in surface seafloor sediments extending 15 miles from the wellhead (Valentine et al. 2014).

Diversity Takes a Nose Dive

Few people ever see the bottom of the deep ocean. So what do these impacted areas actually look like? Starting several months after the leaking well was capped, researchers used ROVs and special cameras to dive down roughly 4,500 feet. They found multiple deep-sea coral colonies showing recent signs of poor health, stress, and tissue damage. On these corals, the polyps, which normally extend frilly tentacles from the corals’ branching arms, were pulled back, and excessive mucus hung from the corals’ skeletons, which also revealed patches of dead tissue. All of these symptoms have been observed in corals experimentally exposed to crude oil (White et al. 2012 PDF).

Five photos of deep-sea coral showing the progression of impacts over several years.

A time series of coral showing the progression of typical impacts at a site of coral colonies located less than seven miles from the source of Deepwater Horizon oil. You can see the brown “floc” material present in November 2010 disappears by March 2011 and afterward, is replaced by fuzzy gray hydroids and the coral loses its brittlestar companion. (Credit: Hsing et al. 2013)

Many of these coral colonies were partly or entirely coated in a clumpy brown material, which researchers referred to as “floc.” Chemical analysis of this material revealed the presence of petroleum droplets with similar chemical markers to Deepwater Horizon oil. The brittlestars usually associated with these corals also appeared in strange colors and positions. Some entire coral colonies were dead.

Research teams noted these observations only at corals within roughly 16 miles of the wellhead (White et al. 2012 PDF, Fisher et al. 2014). However, many similar coral colonies located further from the spill site showed no poor health effects.

Even one and two years later, deep-sea corals within the footprint of the spill still had not recovered. Hydroids took the place of the brown floc material on affected corals. Relatives of jellies, hydroids are fuzzy, grayish marine invertebrates that are known to encrust unhealthy coral.

Life on and under the sediment at the bottom of the Gulf also suffered, with the diversity of a wide range of marine life dropping across an area roughly three times the size of Manhattan (Montagna et al. 2013). Notably, numbers of tiny, pollution-tolerant nematodes increased in areas of moderate impact but at the expense of the number and types of other species, particularly copepods, small crustaceans at the base of the food chain. These effects were related to the concentration of oil compounds in sediments and to the distance from the Deepwater Horizon spill but not to natural oil seeps.

Top row, from left,  two types of crustaceans and a mollusk. Bottom row shows three types of marine worms known as polychaetes.

Examples of some of the common but very small marine invertebrates found living on and under the Gulf of Mexico seafloor. The top row shows, from left, two types of crustaceans and a mollusk, which are more sensitive to pollution. The bottom row shows three types of marine worms known as polychaetes, which tended to dominate ocean sediments with higher oil contamination found near corals. (Courtesy of Paul Montagna, Texas A&M University)

More sensitive to pollution, fewer types and numbers of crustaceans and mollusks were found in sediments around coral colonies showing impacts. Instead, a few types of segmented marine worms known as polychaetes tended to dominate ocean sediments with higher oil contamination near these corals (Fisher et al. 2014).

A Long Time Coming

Life on the bottom of the ocean moves slowly. Deep-sea corals live for hundreds to thousands of years, and their deaths are rare events. Some of the corals coated in oily brown floc are about 600 years old (Prouty et al. 2014). The observed impacts to life in the deep ocean are tied closely to the Deepwater Horizon oil spill, but the full extent of the harm and the eventual recovery may take years, even decades, to manifest (Fisher and Demopoulos, et al. 2014).

Learn more about the studies supported by the federal government’s Natural Resource Damage Assessment for the Deepwater Horizon oil spill, which determines the environmental harm due to the oil spill and response and seeks compensation from those responsible in order to restore the affected resources.


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For Alaska’s Remote Pribilof Islands, a Tale of Survival and Restoration for People and Seals

Set in the middle of Alaska’s Bering Sea, a string of five misty islands known as the Pribilof Islands possess a long, rich, and at times, dark history. A history of near extinction, survival, and restoration for both people and nature. A history involving Alaska Natives, Russians, the U.S. government and military, and seals.

It begins with the native people, known as the Unangan, who live there. They tell a story that, as they say, belongs to a place, not any one person. The story is of the hunter Iggadaagix, who first found these islands many years ago after being swept away in a storm and who wanted to bring the Unangan back there from the Aleutian Islands. When the Unangan finally did return for good, it was in the 18th century, and their lives would become intimately intertwined with those of the northern fur seals (Callorhinus ursinus). Each summer roughly half of all northern fur seals breed and give birth in the Pribilof Islands.

Map of fur seal distributions in Bering Sea and Pacific Ocean, with location of Pribilof Islands.

An 1899 map of the distribution (in red) and migrations of the American and Asiatic Fur Seal Herds in the Bering Sea and North Pacific Ocean. Based on data collected 1893-1897. The Pribilof Islands (St. Paul and St. George) are visible north of the main Aleutian Islands, surrounded by the center collections of red dots. Click to enlarge. (U.S. Government)

But these seals and their luxurious fur, along with the tale of Iggadaagix, would eventually bring about dark times for the seals, the Unangan, and the islands themselves. After hearing of Iggadaagix and searching for a new source of furs, Russian navigator Gavriil Loginovich Pribylov would land in 1786 on the islands which would eventually bear his name. He and others would bring the Unangan from the Aleutian Islands to the Pribilof’s St. George and St. Paul Islands, where they would be put to work harvesting and processing the many fur seals.

In these early years on the islands, Russian hunters so quickly decimated the fur seal population that the Russian-American Company, which held the charter for settling there, suspended hunting from 1805 to 1810. The annual limit for taking fur seals was then set at 8,000 to 10,000 pelts, allowing the population to rebound significantly.

The United States Arrives at the Islands

Fast forward to 1867, when the United States purchased Alaska, including the Pribilof Islands, from Russia for $7.2 million.

Some people considered the lucrative Pribilof Islands fur seal industry to have played a role in this purchase. In fact, this industry more than repaid the U.S. government for Alaska’s purchase price, hauling in $9,473,996 between 1870 and 1909.

The late 19th and early 20th centuries saw various U.S. military branches establish stations on the Pribilof Islands, as well as several (at times unsuccessful) attempts to control the reckless slaughter of fur seals. From 1867 until 1983, the U.S. government managed the fur seal industry on the Pribilof Islands.

In 1984, the Unangan finally were granted control of these islands, but the government had left behind a toxic legacy from commercial fur sealing and former defense sites: hazardous waste sites, dumps, contaminants, and debris.

Making Amends with the Land

This is where NOAA comes into the picture. In 1996, the Pribilof Islands Environmental Restoration Act called on NOAA to restore the environmental degradation on the Pribilof Islands. In particular, a general lack of historical accountability on the islands had led to numerous diesel fuel spills and leaks and improperly stored and disposed waste oils and antifreeze. By 1997 NOAA had removed thousands of tons of old cars, trucks, tractors, barrels, storage tanks, batteries, scrap metal, and tires from St. Paul and St. George Islands. Beginning in 2002, NOAA’s efforts transitioned to cleaning up soil contamination and assessing potential pollution in groundwater.

However, the Department of Defense has also been responsible for environmental cleanup at the Pribilof Islands. The U.S. Army occupied the islands during World War II and left behind debris and thousands of 55-gallon drums, which were empty by 1985 but had previously contained petroleum, oils, and lubricants, which could have leaked into the soil.

By 2008, NOAA’s Office of Response and Restoration had fulfilled its responsibilities for cleaning up the contamination on the Pribilof Islands, closing a dark chapter for this remote and diverse area of the world and hopefully continuing the healing process for the Unangan and fur seals who still call these islands their home.

Learn More about the Pribilof Islands

Man posing with schoolchildren.

Dr. G. Dallas Hanna with a class of Aleut schoolchildren on St. George Island, Alaska, circa 1914. (National Archives)

You can dig even deeper into the wealth of historical information about the Pribilof Islands at pribilof.noaa.gov.

There you can find histories, photos, videos, and documents detailing the islands’ various occupations, the fur seal industry, the relocation of the Unangan during World War II, the environmental contamination and restoration, and more.

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