NOAA's Response and Restoration Blog

An inside look at the science of cleaning up and fixing the mess of marine pollution

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

12 Comments

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.

Author: Ashley Braun

Ashley Braun is the Web Editor for NOAA's Office of Response and Restoration (OR&R). That means she writes and edits a good portion of what appears on OR&R’s web pages, blog, and social media.

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

  1. Thank you for your article. Can you direct me to any sources of information on the edibility of seafood from the Gulf and its estuaries?

  2. Thank-YOU, MS ASHLEY for this VERY GREAT (but aggravating article about oil Co’s boo-boo)…..TOO bad mankind in NOT permitted to use electric powered vehicles….and NOT be dependent on OIL companies, eh?,. The OIL company “BIG BOYS” prevented the electric-powered cars I was told. Do YOU know about this?

    MERCI!

  3. Clean up this mess. Between USA, JAPAN, CHINA AND REPUBLICANS. WE HAVE OCEANS AND DRINKING WATER THAT IS LETHAL. MAJOR SCREW UPS.MARINE LIFE IS DYING SO FAST. YOU PEOPLE NEED TO FIX THIS FREAKING DISASTER. YOU HAVE MADE OUR LIVES HELL

  4. Check out the film; “Who Killed the Electric Car?” Also, I have heard there was a patent on an engine that would get 100 mpg of gas that an oil company bought and sat on so it would not be manufactured en mass. This is akin to evil. We are facing the sixth mass species extinction and it is the only one that is human caused; due to greed by the fossil fuel, mining, logging, and big agriculture industries; greed. It’s time for the people to lead us into the direction of “The Great Healing” or we will forever carry the shame of destroying our delicate biosphere.

  5. Has NOAA given this report and findings to local communities in the Gulf? Shouldn’t BP be paying not only for this type of research but also for the restoration of the underwater habitat?

  6. Can this really ever be cleaned up?? An oil spill like this could happen in the Great Lakes if the 63 year old pipeline breaks. And that’s 1/5 of the worlds fresh water.

  7. I don’t understand why it is taking so long to help these sick dolphins in the first place. At the first sign of being ill, something should have been done. I can’t believe it took five years to see the first signs of distress from the dolphin’s.

    • Hi Lynda,

      The state and federal trustees, including our scientific colleagues at universities and institutions around the Gulf, are engaged in a rigorous, scientific process of injury assessment (known as Natural Resource Damage Assessment) and are still analyzing the data, conducting studies, and evaluating what happened. The trustees (as stewards of the affected natural resources) began planning these studies while the Macondo well was still leaking. The first round of health assessments began the summer after the well was capped. These studies, which have taken place at different times over the past five years, aim to understand and verify the potential impacts to dolphins and other marine life affected by the oil spill, which will inform the restoration required to help these creatures.

      Our obligation under the Oil Pollution Act is to restore the public’s natural resources injured by the Deepwater Horizon spill to the condition they would have been in but for the spill and to compensate the public for the services of those natural resources that were injured or lost. In addition to assessing the damage, we are undertaking early restoration and developing a long-term restoration plan with public involvement to meet that responsibility.

      The assessment is a thorough and time-consuming process by which we evaluate the best scientific evidence available to ensure we understand the injuries caused by the spill, as well as the most appropriate means to restore for those injuries and to compensate for the lost use of the Gulf’s resources while they are injured. The restoration planning effort involves a great deal of public outreach to ensure we consider the public’s perspective when making restoration decisions. You can learn more and stay tuned to the restoration efforts here: http://www.gulfspillrestoration.noaa.gov/

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s