NOAA's Response and Restoration Blog

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


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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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Post Hurricane Sandy, NOAA Aids Hazardous Spill Cleanup in New Jersey and New York

Oil sheen is visible on the waters of Arthur Kill on the border of New Jersey and New York in the wake of Hurricane Sandy.

Oil sheen is visible on the waters of Arthur Kill on the border of New Jersey and New York in the wake of Hurricane Sandy. (NOAA)

[UPDATED NOVEMBER 6, 2012] Hurricane Sandy’s extreme weather conditions—80 to 90 mph winds and sea levels more than 14 feet above normal—spread oil, hazardous materials, and debris across waterways and industrial port areas along the Mid Atlantic. NOAA’s Office of Response and Restoration is working with the U.S. Coast Guard and affected facilities to reduce the impacts of this pollution in coastal New York and New Jersey.

We have several Scientific Support Coordinators and information management specialists on scene at the incident command post on Staten Island, N.Y.

Since the pollution response began, we have been dispatching observers in helicopters with the Coast Guard to survey the resulting oil sheens on the water surface in Arthur Kill, N.J./N.Y. This is in support of the response to a significant spill at the Motiva Refinery in Sewaren, N.J., as well as for the cleanup and assessment of several small spills of diesel fuel, biodiesel, and various other petroleum products scattered throughout northern New Jersey’s refinery areas.

One of the challenges facing communities after a devastating weather event is information management. One tool we have developed for this purpose is ERMA, an online mapping tool which integrates and synthesizes various types of environmental, geographic, and operational data. This provides a central information hub for all individuals involved in an incident, improves communication and coordination among responders, and supplies resource managers with the information necessary to make faster and better informed decisions.

ERMA has now been adopted as the official common operational platform for the Hurricane Sandy pollution response, and we have sent additional GIS specialists to the command post.

Species and Habitats at Risk

The most sensitive habitats in the area are salt marshes, which are often highly productive and are important wildlife habitat and nursery areas for fish and shellfish. Though thin sheens contain little oil, wind and high water levels after the storm could push the diesel deep into the marsh, where it could persist and contaminate sediments. Because marshes are damaged easily during cleanup operations, spill response actions will have to take into account all of these considerations.

In addition, diesel spills can kill the many small invertebrates at the base of the food chain which live in tidal flats and salt marshes if they are exposed to a high enough concentration. Resident marsh fishes, which include bay anchovy, killifish, and silversides, are the fish most at risk because they are the least mobile and occupy shallow habitats. Many species of heron nest in the nearby inland marshes, some of the last remaining marshlands in Staten Island. Swimming and diving birds, such as Canada geese and cormorants, are also vulnerable to having their feathers coated by the floating oil, and all waterfowl have the potential to consume oil while feeding.

Based on the risks to species and habitats from both oil and cleanup, we weigh the science carefully before making spill response recommendations to the Coast Guard.

Tracking the Spilled Oil

Responders face an oily debris field in Sheepshead Bay, N.Y., after Hurricane Sandy. Nov. 2, 2012.

Responders face an oily debris field in Sheepshead Bay, N.Y., after Hurricane Sandy. Nov. 2, 2012. (U.S. Coast Guard)

Because no two oils are alike, we train aerial observers to evaluate the character and extent of oil spilled on the water. NOAA performs these aerial surveys, or overflights, of spilled oil like in Arthur Kill to determine the status of the oil’s source and to track where wind and waves are moving spilled oil while also weathering it. The movement of wind and waves, along with sunlight, works to break down oil into its chemical components. This changes the appearance, size, and location of oil, and in return, can change how animals and plants interact with the oil.

When spilled on water, diesel oil spreads very quickly to a thin film. However, diesel has high levels of toxic components which dissolve fairly readily into the water column, posing threats to the organisms living there. Biodiesel can coat animals that come into contact with it, but it breaks down up to four times more quickly than conventional diesel. At the same time, this biodegradation could cause potential fish kills by using up large amounts of oxygen in the water, especially in shallow areas.

Look for photos, maps, and updates on pollution-related response efforts at IncidentNews.

Check the Superstorm Sandy CrisisMap for aggregated information from NOAA, FEMA, and other sources on weather alerts and observations; storm surge and flood water data; aerial damage assessment imagery; and the locations of power outages, food and gas in New Jersey, and emergency shelters.