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Latest Research Finds Serious Heart Troubles When Oil and Young Tuna Mix

This story was first published on March 26, 2014. It was updated April 9, 2015 to reflect additional research.

Atlantic bluefin tuna prepares to eat a smaller fish.

Atlantic bluefin tuna are a very ecologically and economically valuable species. However, populations in the Gulf of Mexico are at historically low levels. (Copyright: Gilbert Van Ryckevorsel/TAG A Giant)

In May of 2010, when the Deepwater Horizon rig was drilling for oil in the open waters of the Gulf of Mexico, schools of tuna and other large fish would have been moving into the northern Gulf. This is where, each spring and summer, they lay delicate, transparent eggs that float and hatch near the ocean surface. After the oil well suffered a catastrophic blowout and released 3.19 million barrels of oil into the Gulf, these fish eggs may have been exposed to the huge slicks of oil floating up through the same warm waters.

An international team of researchers from NOAA, Stanford University, the University of Miami, and Australia recently published a study in the journal Proceedings of the National Academy of Sciences exploring what happens when tuna mix with oil early in life.

“What we’re interested in is how the Deepwater Horizon accident in the Gulf of Mexico would have impacted open-ocean fishes that spawn in this region, such as tunas, marlins, and swordfishes,” said Stanford University scientist Barbara Block.

This study is part of ongoing research to determine how the waters, lands, and life of the Gulf of Mexico were harmed by the Deepwater Horizon oil spill and response. It also builds on decades of research examining the impacts of crude oil on fish, which began after the 1989 Exxon Valdez oil spill in Alaska. Based on those studies, NOAA and the rest of the research team knew that crude oil—including oil from the Deepwater Horizon oil spill (Incardona et al. 2013)—was toxic to young fish and taught them to look carefully at their developing hearts.

“One of the most important findings was the discovery that the developing fish heart is very sensitive to certain chemicals derived from crude oil,” said Nat Scholz of NOAA’s Northwest Fisheries Science Center.

This is why in this latest study they examined oil’s impacts on young bluefin tuna, yellowfin tuna, and amberjack, all large fish that hunt at the top of the food chain and reproduce in the warm waters of the open ocean. The researchers exposed fertilized fish eggs to small droplets of crude oil collected from the surface and the wellhead from the Deepwater Horizon spill, using concentrations comparable to those during the spill. Next, they put the transparent eggs and young fish under the microscope to observe the oil’s impacts at different stages of development. Using a technology similar to doing ultrasounds on humans, the researchers were able create a digital record of the fishes’ beating hearts.

All three species of fish showed dramatic effects from the oil, regardless of how weathered (broken down) it was. Severely malformed and malfunctioning hearts was the most severe impact. Depending on the oil concentration, the developing fish had slow and irregular heartbeats and excess fluid around the heart. Other serious effects, including spine, eye, and jaw deformities, were a result of this heart failure. (Incardona et al. 2014 [PDF])

Top: A normal young yellowfin tuna. Bottom: A deformed yellowfin tuna exposed to oil during development.

A normal yellowfin tuna larva not long after hatching (top), and a larva exposed to Deepwater Horizon crude oil as it developed in the egg (bottom). The oil-exposed larva shows a suite of abnormalities including excess fluid building up around the heart due to heart failure and poor growth of fins and eyes. (NOAA)

“Crude oil shuts down key cellular processes in fish heart cells that regulate beat-to-beat function,” noted Block, referencing another study by this team, (Brette et al. 2014).

As the oil concentration, particularly the levels of polycyclic aromatic hydrocarbons (PAHs), went up, so did the severity of the effects on the fish. Severely affected fish with heart defects are unlikely to survive. Others looked normal on the outside but had underlying issues like irregular heartbeats. This could mean that while some fish survived directly swimming through oil, heart conditions could follow them through life, impairing their (very important) swimming ability and perhaps leading to an earlier-than-natural death.

“The heart is one of the first organs to appear, and it starts beating before it’s completely built,” said NOAA Fisheries biologist John Incardona. “Anything that alters heart rhythm during embryonic development will likely impact the final shape of the heart and the ability of the adult fish to survive in the wild.”

Even at low levels, oil can have severe effects on young fish, not only in the short-term but throughout the course of their lives. This is why the research team, composed of scientists from NOAA, Stanford University, and the University of Miami, is studying fish exposed to low levels of crude oil as embryos that subsequently grow into juveniles and adults in clean water. Initial research has shown that subtle disruptions of the embryonic heartbeat can produce permanent changes in heart shape that negatively affect swimming performance and other behaviors critical for fish survival. The team has shown similar underlying effects on juvenile mahi mahi (Mager et al. 2014), and studies are ongoing using zebrafish.

These subtle but serious impacts are a lesson still obvious in the recovery of marine animals and habitats still happening 25 years after the Exxon Valdez oil spill.

Find the most up-to-date summary of NOAA-funded research on crude oil’s potential effects on fish in the Gulf Mexico.


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Detecting Change in a Changing World: 25 Years After the Exxon Valdez Oil Spill

Life between high and low tide along the Alaskan coast is literally rough and tumble.

The marine animals and plants living there have to deal with both crashing sea waves at high tide and the drying heat of the sun at low tide. Such a life can be up and down, boom and bust, as favorable conditions come and go quickly and marine animals and plants are forced to react and repopulate just as quickly.

But what happens when oil from the tanker Exxon Valdez enters this dynamic picture—and 25 years later, still hasn’t completely left? What happens when bigger changes to the ocean and global climate begin arriving in these waters already in flux?

Telling the Difference

Two people wearing chest waders sift for marine life in shallow rocky waters.

In 2011 NOAA marine biologist Gary Shigenaka (right) sifts through the sediments of Alaska’s Lower Herring Bay, looking for the tiny marine life that live there. (Photo by Gerry Sanger/Sound Ecosystem Adventures)

In the 25 years since the Exxon Valdez oil spill hit Alaska’s Prince William Sound, NOAA scientists, including marine biologist Gary Shigenaka and ecologist Alan Mearns, have been studying the impacts of the spill and cleanup measures on these animals and plants in rocky tidal waters.

Their experiments and monitoring over the long term revealed a high degree of natural variability in these communities that was unrelated to the oil spill. They saw large changes in, for example, numbers of mussels, seaweeds, and barnacles from year to year even in areas known to be unaffected by the oil spill.

This translated into a major challenge. How do scientists tell the difference between shifts in marine communities due to natural variability and those changes caused by the oil spill?

Several key themes emerged from NOAA’s long-term monitoring and subsequent experimental research:

  • impact. How do we measure it?
  • recovery. How do we define it?
  • variability. How do we account for it?
  • subtle connection to large-scale oceanic influences. How do we recognize it?

What NOAA has learned from these themes informs our understanding of oil spill response and cleanup, as well as of ecosystems on a larger scale. None of this, however, would have been apparent without the long-term monitoring effort. This is an important lesson learned from the Exxon Valdez experience: that monitoring and research, often viewed as an unnecessary luxury in the context of a large oil spill response, are useful, even essential, for framing the scientific and practical lessons learned.

Remote Possibilities

As NOAA looks ahead to the future—and with the Gulf of Mexico’s Deepwater Horizon oil spill in our recent past—we can incorporate and apply lessons of the Exxon Valdez long-term program into how we will support response decisions and define impact and recovery.

The Arctic is a region of intense interest and scrutiny. Climate change is opening previously inaccessible waters and dramatically shifting what scientists previously considered “normal” environmental conditions. This is allowing new oil production and increased maritime traffic through Arctic waters, increasing the risk of oil spills in remote and changing environments.

If and when something bad happens in the Arctic, how do scientists determine the impact and what recovery means, if our reference point is a rapidly moving target? What is our model habitat for restoring one area impacted by oil when the “unimpacted” reference areas are undergoing their own major changes?

Illustrated infographic showing timeline of ecological recovery after the Exxon Valdez oil spill.

Tracking the progress of recovery for marine life and habitats following the Exxon Valdez oil spill is no easy task. Even today, not all of the species have recovered or we don’t have enough information to know. (NOAA) Click to enlarge.

Listening in

NOAA marine biologist Gary Shigenaka explores these questions as he reflects on the 25 years since the Exxon Valdez oil spill in the following Making Waves podcast from the National Ocean Service:

[NARRATOR] This all points back at what Gary says is the main take-away lesson after 25 years of studying the aftermath of this spill: the natural environment in Alaska and in the Arctic are rapidly changing. If we don’t understand that background change, then it’s really hard to say if an area has recovered or not after a big oil spill.

[GARY SHIGENAKA] “I think we need to really keep in mind that maybe our prior notions of recovery as returning to some pre-spill or absolute control condition may be outmoded. We need to really overlay that with the dynamic changes that are occurring for whatever reason and adjust our assessments and definitions accordingly. I don’t have the answers for the best way to do that. We’ve gotten some ideas from the work that we’ve done, but I think that as those changes begin to accelerate and become much more marked, then it’s going to be harder to do.”

 

Read a report by Gary Shigenaka summarizing information about the Exxon Valdez oil spill and response along with NOAA’s role and research on its recovery over the past 25 years.


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After the Big Spill, What Happened to the Ship Exxon Valdez?

This is a post by Gary Shigenaka, a marine biologist with NOAA’s Office of Response and Restoration.

Close-up of the ship's name on side of Exxon Valdez.

The last days of the Exxon Valdez: in the San Diego shipyard before the first name change. Photo from the collection of Gary Shigenaka, NOAA.

A popular myth exists that it is bad luck to rename a boat.  It is unclear whether this applies to “boats” as big as a 987-foot-long oil tanker, but it is possible that the ship originally known as the Exxon Valdez might be used to argue that the answer is “yes.”

When the Exxon Valdez was delivered to Exxon on December 11, 1986, it was the largest vessel ever built on the west coast of the U.S. On July 30, 1989, four months after it ran aground in Alaska’s Prince William Sound and caused the then-largest oil spill in U.S. waters, the crippled Exxon Valdez entered dry dock at National Steel and Shipbuilding in San Diego—its original birthplace.

The trip south from Prince William Sound had not been without incident. Divers discovered hull plates hanging from the frame 70 feet below the surface that had to be cut away, and a 10 mile oil slick trailing behind the ship for a time prevented it from entering San Diego Bay.

New Law, New Name

Ship Exxon Mediterranean in Trieste, Italy, July 1991.

Exxon Mediterranean in Trieste, Italy, July 1991. Photo by Arki Wagner, used with permission.

Nearly a year and $30 million later, the ship emerged for sea trials as the Exxon Mediterranean.  The Exxon Valdez had suffered the ignominy—and corporate hardship—of effectively being singled out in U.S. legislation (the Oil Pollution Act of 1990 [PDF]) and banned from a specific U.S. body of water:

SEC. 5007. LIMITATION.

Notwithstanding any other law, tank vessels that have spilled more than 1,000,000 gallons of oil into the marine environment after March 22, 1989, are prohibited from operating on the navigable waters of Prince William Sound, Alaska.

(33 U.S.C. § 2737)

With this banishment institutionalized in U.S. law, Exxon Shipping Company shifted the operational area for the ship to the Mediterranean and the Middle East and renamed it accordingly.  In 1993, Exxon spun off its shipping arm to a subsidiary, Sea River Maritime, Inc., and the Exxon Mediterranean became the Sea River Mediterranean.  This was shortened to S/R Mediterranean.

In 2002, the ship was re-assigned to Asian routes and then temporarily mothballed in an undisclosed location.

A Ship Singled Out?

Exxon filed suit in federal court challenging the provisions of the Oil Pollution Act of 1990 that had banned its tanker from the Prince William Sound trade route.  In November 2002, the Ninth Circuit Court of Appeals upheld the Oil Pollution Act and its vessel prohibition provision (the Justice Department noting that to that time, 18 vessels had been prevented from entering Prince William Sound).  While Sea River had argued that the law unfairly singled out and punished its tanker, and that there was no reason to believe that a tanker guilty of spilling in the past would spill in the future, the three-judge panel disagreed unanimously.

The Oil Pollution Act of 1990, the landmark law resulting from the Exxon Valdez oil spill, legislated the phase-out of all single-hulled tankers from U.S. waters by 2015. On October 21, 2003, single-hulled tankers carrying heavy oils were banned by the European Union.  A complete ban on single-hulled tankers was to be phased in on an accelerated schedule in 2005 and 2010. There remains pressure to eliminate single-hulled tankers from the oil trade worldwide, so their days are clearly numbered.

In 2005, the S/R Mediterranean was reflagged under the Marshall Islands after having remained a U.S.-flagged ship for 20 years (reportedly in the hopes that it eventually would have been permitted to re-enter the Alaska – U.S. West Coast – Panama route for which it had been designed).  The ship’s name became simply Mediterranean.

In 2008, ExxonMobil and its infamous tanker finally parted ways when Sea River sold the Mediterranean to a Hong Kong-based shipping company, Hong Kong Bloom Shipping Co., Ltd. The ship was once again renamed, to Dong Fang Ocean, and reflagged under Panamanian registry.  Its days as a tanker also came to an end, as the Dong Fang Ocean was converted into a bulk ore carrier at Guangzhou CSSC-Oceanline-GWS Marine Engineering Co., Ltd., China.

The Dong Fang Ocean labored in relative anonymity in its new incarnation until November 29, 2010.  On that day, it collided with another bulk carrier, the Aali in the Yellow Sea off Chengshan, China. Both vessels were severely damaged; the Dong Fang Ocean lost both anchors, and the Aali sustained damage to its ballast tanks.  The Dong Fang Ocean moved to the port of Longyan with assistance by tugs.

The End Is Near

With this last misfortune, the final countdown to oblivion began in earnest for the vessel-formerly-known-as-Exxon-Valdez.  In March 2011, the ship was sold for scrap to a U.S.-based company called Global Marketing Systems (GMS). GMS in turn re-sold it to the Chinese-owned Best Oasis, Ltd., for $16 million.

Exxon Valdez/Exxon Mediterranean/Sea River Mediterranean/S/R Mediterranean/Mediterranean/Dong Fang Ocean/Oriental Nicety being dismantled on the beach of Alang, India, 2012.

Exxon Valdez/Exxon Mediterranean/Sea River Mediterranean/S/R Mediterranean/Mediterranean/Dong Fang Ocean/Oriental Nicety being dismantled in Alang, India, 2012. Photo by ToxicsWatch Alliance.

Intending to bring the Oriental Nicety, as it had been renamed yet one last time, ashore at the infamous shipbreaking beaches of Alang, Gujarat, India, Best Oasis was blocked by a petition filed by Delhi-based ToxicsWatch Alliance with the Indian Supreme Court on the grounds that the ship could be contaminated with asbestos and PCBs. ToxicsWatch Alliance invoked the Basel Convention, which restricts the transboundary movements of hazardous wastes for disposal. However, an environmental audit required by the court showed no significant contamination, and in July 2012, the Oriental Nicety was cleared to be brought ashore for its final disposition. The ship was reportedly beached on August 2, 2012.

Shanta Barley, writing for Nature, penned a wry obituary as a lead-in to her article about the last days of the ship:

The Oriental Nicety (née Exxon Valdez), born in 1986 in San Diego, California, has died after a long struggle with bad publicity.

Editor’s note: Use Twitter to chat directly with NOAA marine biologist Gary Shigenaka about the Exxon Valdez and its impacts on Alaska’s marine life and waters on Monday, March 24 at 3:00 p.m. Eastern. Follow the conversation at #ExxonValdez25 and get the details: http://1.usa.gov/1iw2Y6W.

Gary Shigenaka.

Gary Shigenaka.

Gary Shigenaka is one of the original biological support specialists in the Emergency Response Division of NOAA’s Office of Response and Restoration. Even though his career with NOAA has spanned decades, Gary’s spill response experience began with the Exxon Valdez. He has worked countless spills since then, in the U.S. and internationally. He also currently oversees a number of response-related research efforts and represents the U.S. Department of Commerce on the Region 10 Regional Response Team.