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


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How Do Oil Spills Affect Sea Turtles?

Head and upper body of Kemp's Ridley sea turtle coated in thick brown oil.

A Kemp’s Ridley sea turtle covered in oil from the Deepwater Horizon oil spill in the Gulf of Mexico. (NOAA)

Sea turtles: These beloved marine reptiles have been swimming the seas for millions of years. Yet, in less than a hundred years, threats from humans, such as accidentally catching turtles in fishing gear (“bycatch”), killing nesting turtles and their eggs, and destroying habitat, have caused sea turtle populations to plummet. In fact, all six species of sea turtles found in U.S. waters are listed as threatened or endangered under the U.S. Endangered Species Act.

As we’ve seen in the Gulf of Mexico in recent years, oil spills represent yet another danger for these air-breathing reptiles that rely on clean water and clean beaches. But how exactly do oil spills affect sea turtles? And what do people do during and after an oil spill to look out for the well-being of sea turtles?

Living the Ocean Life

From the oil itself to the spill response and cleanup activities, a major oil spill has the potential to have serious negative effects on sea turtles. Part of the reason for this is because sea turtles migrate long distances and inhabit so many different parts of the ocean environment at different stages of their lives.

Graphic showing the life cycle of sea turtles in the ocean: egg laying; hatchling dispersal; oceanic feeding: small juveniles in sargassum; feeding on the continental shelf: large juveniles and adults, mating and breeding migration; and internesting near beach.

The life cycle of a sea turtle spans multiple habitats across the ocean, from sandy beaches to the open ocean. (NOAA)

For starters, sea turtles hatch (and females later return as adults to lay eggs) on sandy beaches. Then, they head to the vast open ocean where the tiny young turtles drift, hide from predators, and grow among floating islands of seaweed called sargassum. Finally, as larger juveniles and adults, they swim to the shallower waters of the continental shelf and near shore, where they spend the majority of the rest of their lives.

If a large offshore spill releases oil into the open ocean, currents and winds can carry oil across all of the habitats where sea turtles are found—and into the potential path of sea turtles of every age—as it makes its way to shore.

Another reason sea turtles can be particularly vulnerable to ocean oil spills is simply because they breathe air. Even though sea turtles can hold their breath on dives for extended periods of time, they usually come to the surface to breathe several times an hour. Because most oils float, sea turtles can surface into large oil slicks over and over again.

The situation can be even worse for very young sea turtles living among floating sargassum patches, as these small turtles almost never leave the top few feet of water, increasing their exposure to a floating oil slick. Furthermore, ocean currents and winds often bring oil to the same oceanic convergence zones that bring sargassum and young sea turtles together.

Turtle Meets Oil, Inside and Out

So, we know the many places sea turtles can run into an oil spill, but how exactly do they encounter the oil during a spill?

Graphic showing how spilled oil in the ocean can affect sea turtles at all stages of life and across ocean habitats: Oil on the shoreline can contaminate nesting females, nests, and hatchlings; larger turtles can inhale oil vapors, ingest oil in prey or sediment, and become coated in oil at the surface; winds and currents create ocean fronts, bringing together oil, dispersants, and sargassum communities, causing prolonged floating oil exposure; juvenile turtles ingest oil, inhale vapors, and become fatally mired and overheated; prey items may also be killed by becoming stuck in heavy oil or by dissolved oil components; and sargassum fouled by oil and dispersants can sink, leaving sargassum-dependent animals without food and cover and vulnerable to predators. Dead sea turtles may sink.

The potential impacts of an oil spill on sea turtles are many and varied. For example, some impacts can result from sea turtles inhaling and ingesting oil, becoming covered in oil to the point of being unable to swim, or losing important habitat or food that is killed or contaminated by oil. (NOAA)

It likely starts when they raise their heads above the water’s surface to breathe. When sea turtles surface in a slick, they can inhale oil and its vapors into their lungs; gulp oil into their mouths, down their throats, and into their digestive tracts while feeding; and become coated in oil, to the point of becoming entirely mired and unable to swim. Similarly, sea turtles may swim through oil drifting in the water column or disturb it in the sediments on the ocean bottom.

Female sea turtles that ingest oil can even pass oil compounds on to their developing young, and once laid, the eggs can absorb oil components in the sand through the eggshell, potentially damaging the baby turtle developing inside. Nesting turtles and their hatchlings are also likely to crawl into oil on contaminated beaches.

Not the Picture of Health

Graphic showing how oil spill cleanup and response activities can negatively affect sea turtles: Cleaning oil from surface and subsurface shores with large machines deters nesting; booms and other barriers prevent females from nesting; response vessels can strike and kill sea turtles and relocation trawlers can inadvertently drown them; application of dispersants may have effects on sea turtles; and skimming and burning heavy oil may kill some sea turtles, while also exposing others to smoke inhalation.

Oil spill cleanup and response activities can negatively affect sea turtles as well. For example, oil containment booms along beaches can prevent nesting females from reaching the shores to lay their eggs. (NOAA)

Once sea turtles encounter oil, what are the impacts of that exposure?

Inhaling and swallowing oil generally result in negative health effects for animals, as shown in dolphins and other wildlife, hindering their overall health, growth, and survival. Lining the inside of sea turtles’ throats are pointy spines called esophageal papillae, which normally act to keep swallowed food inside while allowing water to be expelled. Unfortunately, these projections also seem to trap thick oil in sea turtles’ throats, and evidence of oil has been detected in the feces of oiled turtles taken into wildlife rehabilitation centers.

Oil can irritate sensitive mucus membranes around the eyes, mouth, lungs, and digestive tract of sea turtles, and toxic oil compounds known as polycyclic aromatic hydrocarbons (PAHs) can be absorbed into vital organ tissues such as the lungs and liver. Because sea turtles can hold their breath for long periods, inhaled oil has a greater chance of being absorbed into their bodies. Oil compounds that get passed from mother turtles to their young can interfere with development and threaten the survival of sea turtles still developing in the eggs.

Once inside their systems, oil can impede breathing and heart function in sea turtles, which can make diving, feeding, migrating, mating, and escaping predators more difficult. Being heavily covered in oil likewise impedes sea turtles’ abilities to undertake these activities, which puts them at risk of exhaustion and dehydration. In addition, dark oil under a hot summer sun can heat up turtles to dangerous temperatures, further jeopardizing their health and even killing them. In fact, sea turtles heavily coated in oil are not likely to survive without medical attention from humans.

Another, less direct way oil spills can affect the health of sea turtles is by killing or contaminating what they eat, which, depending on the species, can range from fish and crabs to jellyfish to seagrass and algae. In addition, if oil kills the sargassum where young sea turtles live, they lose their shelter and source of food and are forced to find suitable habitat elsewhere, which makes them more vulnerable to predators and uses more energy.

Spill response and cleanup operations also can harm sea turtles unintentionally. Turtles can be killed after being struck by response vessels or as a result of oil burning and skimming activities. Extra lighting and activity on beaches can disrupt nesting and hatchling turtles, as well as incubating eggs.

Help Is on the Way

A person holding a small clean Kemp's Ridley sea turtle over a blue bin.

A Kemp’s Ridley sea turtle ready to be returned to the wild after being cleaned and rehabilitated during an oil spill. (NOAA)

The harm that oil spills can cause to sea turtles is significant, and estimating the full suite of impacts to these species is a long and complicated process.  There are some actions that have been taken to protect these vulnerable marine reptiles during oil spills. These include activities such as:

  • Performing rescue operations by boat, which involve scooping turtles out of oil or water using dip-nets and assessing their health.
  • Taking rescued turtles to wildlife rehabilitation centers to be cleaned and cared for.
  • Monitoring beaches and coastlines for injured (and sometimes dead) turtles.
  • Monitoring nesting beaches to safeguard incubating nests.
  • Conducting aerial surveys to assess abundance of adults and large juvenile turtles potentially in the footprint of an oil spill.

Finally, the government agencies acting as stewards on behalf of sea turtles, as well as other wildlife and habitats, will undertake a scientific evaluation of an oil spill’s environmental impacts and identify restoration projects that make up for any impacts.

As an example, read about the impacts to sea turtles from the 2010 Deepwater Horizon oil spill, details about how they were harmed, and the proposed restoration path forward.


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10 Photos That Tell the Story of the Exxon Valdez Oil Spill and its Impacts

Exxon Valdez ship with response vessels in Prince William Sound.

The single-hull tanker Exxon Valdez ran aground on Bligh Reef in Prince William Sound, Alaska, March 24, 1989, spilling 11 million gallons of crude oil. (U.S. Coast Guard)

While oil spills happen almost every day, we are fortunate that relatively few make such large or lasting impressions as the Deepwater Horizon or Exxon Valdez spills. Before 2010, when the United States was fixated on a gushing oil well at the bottom of the Gulf of Mexico, most Americans could probably only name one spill: when the tanker Exxon Valdez released 11 million gallons of crude oil into Alaska’s Prince William Sound on March 24, 1989.

Here we’ve gathered 10 photos that help tell the story of the Exxon Valdez oil spill and its impacts, not only on the environment but also on science, policy, spill response, school kids, and even board games. It has become a touchstone event in many ways, one to be learned from even decades after the fact.

1. Time for safety

Calendar showing March 1989 and image of Exxon Valdez ship.

In an ironic twist of fate, the Exxon Shipping Company’s safety calendar featured the tanker Exxon Valdez in March 1989, the same month the ship ran aground. Image: From the collection of Gary Shigenaka.

Long before the Exxon Valdez tanker ran aground on Bligh Reef in Prince William Sound, a series of events were building that would enable this catastrophic marine accident to unfold as it did. These actions varied from the opening of the Trans-Alaska Pipeline in the 1970s to the decision by the corporation running that pipeline to disband its oil spill response team and Exxon’s efforts to hold up both the tanker Exxon Valdez and its captain, Joseph Hazelwood, as exemplars of safety.

Captain Hazelwood received two Exxon Fleet safety awards for 1987 and 1988, the years leading up to March 1989, which was coincidentally the month the Exxon Valdez was featured on an Exxon Shipping Company calendar bearing the warning to “take time to be careful – now.”

Read more about the timeline of events leading up to the Exxon Valdez oil spill.

2. A law for the birds

Birds killed as a result of oil from the Exxon Valdez spill.

Thanks to the Oil Pollution Act, federal and state agencies can more easily evaluate the full environmental impacts of oil spills — and then enact restoration to make up for that harm. (Exxon Valdez Oil Spill Trustee Council)

Photos of oil-soaked birds and other wildlife in Prince William Sound reinforced just how inadequate the patchwork of existing federal, state, and local laws were at preventing or addressing the Exxon Valdez oil spill.

While lawmakers took nearly a year and a half—and a few more oil spills—to pass the Oil Pollution Act of 1990, this landmark legislation was without a doubt inspired by that major oil spill. (After all, the law specifically “bars from Prince William Sound any tank vessels that have spilled over 1,000,000 gallons of oil into the marine environment after March 22, 1989.” In other words, the Exxon Valdez.) In the years since it passed, this law has made huge strides in improving oil spill prevention, cleanup, liability, and restoration.

3.  The end of single-hull tankers

People observe a large tanker with a huge gash in its hull in dry dock.

Evidence of the success of double-hull tankers: The Norwegian tanker SKS Satilla collided with a submerged oil rig in the Gulf of Mexico in 2009 and despite this damage, did not spill any oil. (Texas General Land Office)

This image of a damaged ship is not showing the T/V Exxon Valdez, and that is precisely the point. The Exxon Valdez was an oil tanker with a single hull, which meant that when it hit ground, there was only one layer of metal for the rocks to tear through and release its tanks of oil.

But this 2009 photo shows the Norwegian tanker SKS Satilla after it sustained a major gash in its double-sided hull — and didn’t spill a drop of oil. Thanks to the Oil Pollution Act of 1990, all new tankers and tank-barges were required to be built with double hulls to reduce the chance of another Exxon Valdez situation. January 1, 2015 was the final deadline for phasing out single-hull tankers in U.S. waters.

 4. Oiled otters and angry kids

Policymakers weren’t the only ones to take note and take action in the wake of the Exxon Valdez oil spill. Second grader Kelli Middlestead of the Franklin School in Burlingame, California, was quite upset that the oil spill was having such devastating effects on one of her favorite animals: sea otters. So, on April 13, 1989, she wrote and illustrated a letter to Walter Stieglitz, Alaskan Regional Director of the U.S. Fish and Wildlife Service, to let him know she felt that the oil spill was “killing nature.”

Indeed, sea otters in Prince William Sound weren’t declared recovered from the Exxon Valdez oil spill until 2013. Other species still haven’t recovered and in some sheltered beaches below the surface, you can still find pockets of oil.

5. Oil and killer whales do mix (unfortunately)

Killer whales swimming alongside boats skimming oil from the Exxon Valdez oil spill.

Killer whales swimming in Prince William Sound alongside boats skimming oil from the Exxon Valdez oil spill (State of Alaska, Dan Lawn).

One of the species that has yet to recover after the Exxon Valdez oil spill is the killer whale, or orca. Before this oil spill, scientists and oil spill experts thought that these marine mammals were able to detect and avoid oil spills. That is, until two killer whale pods were spotted swimming near or through oil from this spill. One of them, a group nicknamed the “AT1 Transients” which feed primarily on marine mammals, suffered an abrupt 40% drop in population during the 18 months following the oil spill.

The second group of affected killer whales, the fish-eating “AB Pod Residents,” lost 33% of their population, and while they have started to rebound, the transients are listed as a “depleted stock” under the Marine Mammal Protection Act and may have as few as seven individuals remaining, down from a stable population of at least 22 in the 1980s.

Building on the lessons of the Exxon Valdez and Deepwater Horizon oil spills, NOAA has developed an emergency plan for keeping the endangered Southern Resident killer whale populations of Washington and British Columbia away from potential oil spills.

6. Tuna troubles

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

A normal yellowfin tuna larva (top), and a larva exposed to Deepwater Horizon crude oil during development (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)

How does crude oil affect fish populations? In the decades since the Exxon Valdez spill, teams of scientists have been studying the long-term effects of oil on fish such as herring, pink salmon, and tuna. In the first couple years after this spill, they found that oil was in fact toxic to developing fish, curving their spines, reducing the size of their eyes and jaws, and building up fluid around their hearts.

As part of this rich research tradition begun after the Exxon Valdez spill, NOAA scientists helped uncover the precise mechanisms for how this happens after the Deepwater Horizon oil spill in 2010. The photo here shows both 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 exhibits a suite of abnormalities, showing how toxic chemicals in oil such as polycyclic aromatic hydrocarbons (PAHs) can affect the embryonic heart. By altering the embryonic heartbeat, exposure to oil can transform the shape of the heart, with implications for how well the fish can swim and survive as an adult.

7. Caught between a rock and a hard place

Mearns Rock boulder in 2003.

The boulder nicknamed “Mearns Rock,” located in the southwest corner of Prince William Sound, Alaska, was coated in oil which was not cleaned off after the 1989 Exxon Valdez oil spill. This image was taken in 2003. (NOAA)

Not all impacts from an oil spill are as easy to see as deformed fish hearts. As NOAA scientists Alan Mearns and Gary Shigenaka have learned since 1989, picking out those impacts from the noisy background levels of variability in the natural environment become even harder when the global climate and ocean are undergoing unprecedented change as well.

Mearns, for example, has been monitoring the boom and bust cycles of marine life on a large boulder—nicknamed “Mearns Rock”—that was oiled but not cleaned after the Exxon Valdez oil spill. What he and Shigenaka have observed on that rock and elsewhere in Prince William Sound has revealed large natural swings in the numbers of mussels, seaweeds, and barnacles, changes which are unrelated to the oil spill as they were occurring even in areas untouched by the spill.

Read more about how these scientists are exploring these challenges and a report on NOAA’s involvement in the wake of this spill.

8. A game culture

A view of part of the board game “On the Rocks: The Great Alaska Oil Spill” with a map of Prince William Sound.

The game “On the Rocks: The Great Alaska Oil Spill” challenges players to clean all 200 miles of shoreline oiled by the Exxon Valdez — and do so with limits on time and money. (Credit: Alaska Resources Library and Information Services, ARLIS)

Just as the Exxon Valdez oil spill touched approximately 200 miles of remote and rugged Alaskan shoreline, this spill also touched the hearts and minds of people far from the spill. References to it permeated mainstream American culture in surprising ways, inspiring a cookbook, a movie, a play, music, books, poetry, and even a board game.

That’s right, a bartender from Valdez, Alaska, produced the board game “On the Rocks: The Great Alaska Oil Spill” as a result of his experience employed in spill cleanup. Players vied to be the first to wash all 200 miles of oiled shoreline without running out of time or money.

9. Carrying a piece of the ship

The rusted and nondescript piece of steel on the left was a piece of the tanker Exxon Valdez, recovered by the salvage crew in 1989 and given to NOAA marine biologist Gary Shigenaka. It was the beginning of his collection of Exxon Valdez artifacts and remains the item with the biggest personal value to him. The piece of metal on the right, inscribed with "On the rocks," is also metal from the ship but was purchased on eBay.

The rusted and nondescript piece of steel on the left was a piece of the tanker Exxon Valdez, recovered by the salvage crew in 1989 and given to NOAA marine biologist Gary Shigenaka. It was the beginning of his collection of Exxon Valdez artifacts and remains the item with the biggest personal value to him. The piece of metal on the right, inscribed with “On the rocks,” is also metal from the ship but was purchased on eBay. (NOAA)

One NOAA scientist in particular, Gary Shigenaka, who kicked off his career working on the Exxon Valdez oil spill, was personally touched by this spill as well. After receiving a small chunk of metal from the ship’s salvage, Shigenaka began amassing a collection of Exxon Valdez–related memorabilia, ranging from a highball glass commemorating the ship’s launch in 1986 (ironic considering the questions surrounding its captain being intoxicated the night of the accident) to the front page of the local paper the day of the spill.

See more photos of his collection.

10. The infamous ship’s fate

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.

After causing the largest-to-date oil spill in U.S. waters, what ever happened to the ill-fated Exxon Valdez ship? It limped back for repairs to San Diego Bay where it was built, but by the time it was sea-ready again, the ship had been banned from Prince William Sound by the Oil Pollution Act and would instead be reassigned to the Mediterranean and Middle East and renamed accordingly, the Exxon Mediterranean.

But a series of new names and bad luck continued to follow this ship, until it was finally sold for scrap in 2011. Under its final name, Oriental Nicety, it was intentionally grounded at the infamous shipbreaking beaches of Alang, Gujarat, India, in 2012 and dismantled in its final resting place 23 years after the Exxon Valdez ran aground half a world away.


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For the First Time in Decades, Scientists Examine How Oil Spills Might Affect Baleen Whales

A North Atlantic right whale's mouth is visible at the ocean surface.

NOAA scientists and partners recently collaborated to examine how oil and dispersants might affect the function of baleen in humpback, bowhead, and right whales (pictured). Hundreds of baleen plates hang from these whales’ top jaws and allow them to filter food from the water. (Credit: Georgia Department of Natural Resources, Permit 15488)

Several days of unseasonably warm weather in late September had Gary Shigenaka starting to wonder how much longer he and his colleagues would be welcome at Ohmsett, a national oil spill research facility in New Jersey.

They were working with whale baleen, and although the gum tissue anchoring their baleen samples had been preserved with formalin, the balmy fall weather was taking a toll. As a result, things were starting to smell a little rank.

Fortunately, cooler weather rounded out that first week of experiments, and the group, of course, was invited back again. Over the course of three week-long trials in September, December, and January, they were trying to tease out the potential impacts of oil and dispersants on whale baleen.

As a marine biologist with NOAA’s Office of Response and Restoration, Shigenaka’s job is to consider how oil spills might threaten marine life and advise the U.S. Coast Guard on this issue during a spill response.

But the last time scientists had examined how oil might affect whale baleen was in a handful of studies back in the 1980s. This research took place before the 1989 Exxon Valdez and 2010 Deepwater Horizon oil spills and predated numerous advances in scientific technique, technology, and understanding.

Thanks to a recent opportunity provided by the U.S. Bureau of Safety and Environmental Enforcement, which runs the Ohmsett facility, Shigenaka and a team of scientists, engineers, and oil spill experts have been able to revisit this question in the facility’s 2.6 million gallon saltwater tank.

The diverse team that made this study possible hails not just from NOAA but also Alaska’s North Slope Borough Department of Wildlife Management (Dr. Todd Sformo), Woods Hole Oceanographic Institution (Dr. Michael Moore and Tom Lanagan), Hampden-Sydney College (Dr. Alexander Werth), and Oil Spill Response Limited (Paul Schuler). In addition, NOAA’s Marine Mammal Health and Stranding Response Program provided substantial support for the project, including funding and regulatory expertise, and was coordinated by Dr. Teri Rowles.

Getting a Mouthful

To understand why this group is focused on baleen and how an oil spill might affect this particular part of a whale, you first need to understand what baleen is and how a whale uses it. Similar to fingernails and hooves, baleen is composed of the protein keratin, along with a few calcium salts, giving it a tough but pliable character.

A hand holds a ruler next to oiled baleen hanging from a clamp next to a man.

Made of the flexible substance keratin, baleen plates have tangles of “fringe hair” that act as nets to strain marine life from mouthfuls of ocean water. This study examined how oil and dispersants might affect the performance of baleen. (NOAA)

Twelve species of whales, including humpback and bowhead, have hundreds of long plates of baleen hanging from the top jaw, lined up like the teeth on a comb, which they use to filter feed. A whale’s tongue rubs against its baleen plates, fraying their inner edges and creating tangles of “fringe hair” that act like nets to catch tiny sea creatures as the whale strains massive gulps of ocean water back out through the baleen plates.

Baleen does vary somewhat between species of whales. Some might have longer or shorter baleen plates, for example, depending on what the whale eats. Bowhead whales, which are Arctic plankton-eaters, can have plates up to 13 feet long.

This study was, at least in part, inspired by scientists wondering what would happen to a bowhead whale if a mouthful of water brought not just lunch but also crude oil from an ill-fated tanker traversing its Arctic waters.

Would oil pass through a whale’s hundreds of baleen plates and coat their mats of fringe hairs? Would that oil make it more difficult for the whale to push huge volumes of water through the oily baleen, causing the whale to use more energy as it tried? Does that result change whether the oil is freshly spilled, or weathered with age, or dispersed with chemicals? Would dispersant make it easier for oil to reach a whale’s gut?

Using more energy to get food would mean the whales then would need to eat even more food to make up for the energy difference, creating a tiring cycle that could tax these gargantuan marine mammals.

Testing this hypothesis has been the objective of Shigenaka’s team. While it might sound simple, almost nothing about the project has been straightforward.

Challenges as Big as a Whale

One of the first challenges was tackled by the engineers at Woods Hole Oceanographic Institution. They were tasked with turning the mechanical features of Ohmsett’s giant saltwater tank into, essentially, a baleen whale’s mouth.

Woods Hole fabricated a special clamp and then worked with the Ohmsett engineering staff to attach it to a corresponding mount on the mechanical bridges that move back and forth over the giant tank. The clamp gripped the sections of baleen and allowed them to be held at different angles as they moved through the water. In addition, this custom clamp had a load cell, which was connected to a computer on the bridge. As the bridge moved the clamp and baleen at different speeds and angles through the water, the team could measure change in drag on the baleen via the load cell.

With the mechanical portion set up, the Ohmsett staff released oil into the test tank on the surface of the water, and the team watched expectantly how the bridges moved the baleen through the thin oil slick. It turned out to be a pretty inefficient way to get oil on baleen. “How might a whale deal with oil on the surface of the water?” asked Shigenaka. “If it’s feeding, it might scoop up a mouthful of water and oil and run it through the baleen.” But how could they simulate that experience?

They tried using paintbrushes to apply crude oil to the baleen, but that seemed to alter the character of the baleen too much, matting down the fringe hairs. After discussions with the Ohmsett engineering staff, the research team finally settled on dipping the baleen into a pool of floating oil that was contained by a floating ring. This set-up allowed a relatively heavy amount of oil to contact baleen in the water and would help the scientists calibrate their expectations about potential impacts.

Testing the Waters

Four black plumes of dispersed oil are released underwater onto long plates of baleen moving behind the applicator.

After mixing chemical dispersant with oil, the research team released plumes of it underwater in Ohmsett’s test tank as baleen samples moved through the water behind the applicator. Researchers also tested the effects of dispersant alone on baleen function. (NOAA)

In all, Shigenaka and his teammates ran 127 different trials across this experiment. They measured the drag values for baleen in a variety of combinations: through saltwater alone, with fresh oil, with weathered oil, with dispersed oil (pre-mixed and released underwater through a custom array designed and built by Ohmsett staff), and with chemical dispersant alone. They tested during temperate weather as well as lower temperature conditions, which clearly thickened the consistency of the oil. They conducted the tests using baleen from three different species of whales: bowhead, humpback, and right whale.

Following all the required regulations and with the proper permits, the bowhead baleen was donated by subsistence whalers from Barrow, Alaska. The baleen from other species came from whales that had stranded on beaches from locations outside of Alaska.

In addition to testing the potential changes in drag on the baleen, the team of researchers used an electric razor to shave off baleen fringe hairs as samples for chemical analysis to determine whether the oil or dispersant had any effects on baleen at the molecular level. They also determined how much oil, dispersed oil, and dispersant were retained on the baleen fringe hairs after the trials.

At this point, the team is analyzing the data from the experimental trials and plans to submit the results for publication in a scientific journal. NOAA is also beginning to create a guidance document on oil and cetaceans (whales and dolphins), which will incorporate the conclusions of this research.

While the scientific community has learned a lot about the apparent effects of oil on dolphins in the wake of the 2010 Deepwater Horizon oil spill, there is very little information on large whales. The body of research on oil’s effects on baleen from the 1980s concluded that there were few and transient effects, but whether that conclusion holds up today remains to be seen.

“This is another piece of the puzzle,” said Shigenaka. “If we can distill response-relevant guidance that helps to mediate spill impacts to whales, then we will have been successful.”

Work was conducted under NOAA’s National Marine Fisheries Service Permits 17350 and 18786.


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What’s It Like Saving Endangered Baby Sea Turtles in Costa Rica?

This is a post by the Office of Response and Restoration’s Valerie Chu.

Three newly hatched Olive Ridley sea turtles crawl across sand.

Newly hatched Olive Ridley sea turtles make their way toward the ocean. (Used with permission of Julie Watanuki)

I was standing on a sandy Costa Rican beach in the dark of night when I received a hard lesson in the challenges of saving an endangered species. It was my first night volunteering during a seven-day stint on a sea turtle conservation project with the Asociación de Voluntarios para el Servicio en Áreas Protegidas (ASVO) in Montezuma, Costa Rica.

I was charged with protecting sea turtle nests in the ASVO hatchery from poachers and hungry wildlife. On the night of my very first shift, I discovered something terrible had happened. A net covering one of the sea turtle nests had been taken off, and when I looked inside, I found the remains of eight dead baby turtles with just their heads bitten off. When I looked in the back of the hatchery, I noticed that some eggs also had been dug up and eaten.

It was heartbreaking, but furthered my resolve to protect these vulnerable turtles.

Later that night, I discovered who the culprits were—two raccoons. Throughout my shift, the two raccoons would sneak back and I would scare them away each time. Fortunately, the raccoons did not come back in the following days. I was grateful I could play a small part in giving young sea turtles a head start in a long and dangerous journey.

Thinking (and Acting) Globally

Rows of nets cover sandy sea turtle nests, surrounded by fencing.

Volunteers with ASVO place sea turtle eggs collected from Costa Rican beaches into a hatchery with nets covering the nests to protect them from poachers, predators, and other threats. The eggs hatch less than two months later. (Used with permission of Valerie Chu)

Ever since I graduated from the University of Washington in 2012, I’ve wanted to make a positive impact on the dwindling populations of endangered species around the world. I started by volunteering to help orphaned and injured wildlife at the PAWS Wildlife Center near Seattle, Washington (where I recently volunteered during a vegetable oil spill).

As I’ve worked with these animals, my desire of making a global impact on wildlife conservation has increased more and more. In December 2015, I finally got my chance to do it when I traveled to Costa Rica to volunteer with ASVO.

ASVO’s primary goal is to promote active conservation in protected areas, beaches, and rural communities of Costa Rica. They have a volunteer program in around 20 different areas of the country, staffed by some 2,300 volunteers, comprising both local and international volunteers from around the world.

Turtle Time

I was working with Olive Ridley sea turtles, a vulnerable species likely to become endangered in the foreseeable future. Their main threats to survival are direct harvest of adults and eggs, incidental capture in commercial fisheries, loss of nesting habitat, and predators.

During nesting season in Costa Rica, people with ASVO patrol the beaches for female turtles laying their eggs and then gather the eggs and place them at a hatchery. This way, the eggs are protected from poachers, predators, and other threats, both human and environmental. The eggs incubate in the hatchery for between 52 and 58 days before hatching.

Because I had arrived at the end of sea turtle nesting season, I mostly handled the hatchlings and released them into the ocean. When the newly hatched turtles had completely emerged from their nests, I would—while wearing a glove—pick up each one from its nest and head to the ocean. I would then set the turtles down on the sand and watch them walk into the ocean. Some turtles would lose their way because they would walk in the wrong direction or get swept aside by a big wave, so it was my job to make sure they found their way to the ocean without mishap.

Most of my turtle volunteer shifts were at night, and because sea turtles are very sensitive to white light, we could only use a red light while handling them. During night shifts, we were always paired with a second person, allowing us to have one person handle the hatched turtles while the other could stand guard at the hatchery (a very important job, as I observed my first night).

After releasing the turtles, I had to record the number of turtles released, the time of the release, and other notes. Each of the nests held roughly 80-100 eggs, and about 50-70 eggs would hatch, which was an incredible sight.

Don’t Stop (Thinking About What You Can Do)

This trip was an absolutely amazing experience for me. By working with these turtles, I began to fulfill my dream of making a global impact on endangered species populations. On top of that, I was able to connect with other people who care about these issues and form a deep bond over this shared experience.

In the future, I hope to continue volunteering for the conservation of imperiled species like the tiny sea turtles I encountered in Costa Rica. In 2017, I plan to travel to Thailand to work with the endangered elephant population.

But there are lots of ways to protect endangered species at home too. How do you plan to help?

Three people help wash an oiled goose in big soapy wash tubs.

Valerie Chu is an Environmental Scientist who has been providing support for the Office of Response and Restoration’s Emergency Response Division software projects since 2012, when she obtained her undergraduate degree in Environmental Science and Resource Management and then started working with NOAA and Genwest. During her spare time, she volunteers with animal welfare-related causes such as PAWS and Zazu’s House Parrot Sanctuary.


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Why Is It So Hard to Count the Number of Animals Killed by Oil Spills?

Dead bird covered in oil next to spill containment boom on a beach.

Many animals directly killed by oil spills will never be found at all for a number of reasons. Even if people can find a dead animal carcass, it might be too decomposed to tell if oil killed it. (Department of Interior)

After an oil spill along the coast, the impacts might appear to be pretty obvious: oil on beaches, dead birds, oil-coated otters. When conducting a Natural Resource Damage Assessment, it’s our job to measure those environmental impacts and determine what kind of restoration—and how much—is needed to make up for those impacts.

But in general we don’t base those calculations solely on how many animals were observed dead on shorelines, because that would drastically underestimate the total number of animals killed by an oil spill.

Why?

Well, for starters, the length of shoreline where animals might wash up could be very long, isolated, or otherwise difficult to survey. For a large oil spill, imagine trying to study a place as expansive as the Gulf of Mexico. This body of water covers roughly 600,000 square miles and borders five states. Also, significant portions of the shore are wetlands with convoluted shorelines that make searching and finding animals much more difficult than on sandy beaches.

Let Me Count the Ways

Scientists records data on a dead dolphin on a beach.

Oil spills can have indirect effects that don’t necessarily kill animals and plants, at least, not right away, but those impacts can lead to death and health and reproductive problems months or years later. (Credit: Louisiana Department of Fisheries and Wildlife)

Trying to determine the total number of animals that died because of an oil spill offers multiple challenges. Quantifying these impacts to wildlife relies in part on people being able to find, record, and sometimes take samples of dead animal carcasses across an extended distance and length of time.

They then would need to tie those deaths to a particular oil spill, which is part of our responsibility as we assess the environmental harm after a spill. It’s also complicated by the fact that animals die every day for many reasons other than oil spills, due to changes in weather, food supplies, predation, background pollution, and disease.

This difficult undertaking has numerous limitations, and as a result, relying on counts of animal deaths alone can drastically underestimate the actual harm caused by a spill.

Graphic of oil spill in ocean near coast showing the multiple scenarios for the carcasses of animals killed by an oil spill. They include: Discovered carcasses (Of those carcasses that are found, most are too decomposed to determine the cause of death), remote strandings (Animals strand on remote shorelines that humans don't frequent), scavenging (Carcasses attract scavengers, such as sharks, birds, crabs, and others, that consume and remove evidence of dead animals), dying underwater (Some animals may die while underwater and disappear), decomposition (Hot weather causes carcasses to decay quickly in the water and on the shore), sinking (Carcasses may sink), and winds, currents, and distance from shore (These factors impact the movement of animals toward or away from shore).

The challenge of finding an animal that dies from an oil spill: Only a fraction of the turtles, dolphins, birds, fish, and other animals killed by an oil spill are ever found. (NOAA)

For example, even if people can find a dead animal carcass, it might be too decomposed to tell if oil killed it. But more likely are the scenarios where animals directly killed by oil will never be found at all because they:

  • Are eaten by predators or scavengers.
  • Die underwater.
  • Sink below the ocean surface.
  • Wash ashore in remote areas where people can’t or don’t often go.
  • Are carried out to the open ocean by winds and currents.
  • Decompose before people can observe them.
  • Are too tiny for people to easily observe after they die (e.g., young fish and crustaceans).

Late-Breaking Effects

To make things even more challenging, oil spills can have indirect effects that don’t outright kill animals and plants, at least, not right away. Dealing with exposure to oil can cause a number of damaging impacts, including lung disease (from inhaling oil vapors), stress hormone dysfunction, reduced growth, increased vulnerability to disease, heart failure and deformities in developing fish, and reproductive problems in animals such as dolphins and fish.

These types of effects can lead to other health impacts and sometimes eventually death, with the fallout felt across generations. Simply trying to count the number of dead animal carcasses found immediately after an oil spill would miss these deaths (or births that never happen) that can come months or even years afterward.

Seek and You May or May Not Find

Despite these challenges, it’s still useful to collect dead animal carcasses after an oil spill and use information gained from them to support other approaches for determining broader oil spill impacts.

One such approach takes into account several additional types of data, along with the observations of dead animals, to infer the likely true number of animals killed by an oil spill. These data include different animals’ estimated exposure to oil, health effects observed in laboratory and field studies, and basic information about animal behavior at different stages of life.

For instance, after the 2007 Cosco Busan oil spill in California’s San Francisco Bay, search teams recovered several thousand oiled birds, and additional studies were later performed to determine how many more dead birds were likely killed that were never seen or collected.

In one such study (known as a “Searcher Efficiency Study”), a study team randomly placed 107 real bird carcasses along San Francisco Bay shorelines over the course of three days, and teams were deployed to search for them and collect what they could find. It is surprisingly easy for searchers to miss dead birds on the beach since the animals blend in with other debris or beach wrack, can be hidden by small depressions, or be too far away to recognize.

Since the study team knew the actual number and locations of carcasses deployed for the study, the number that search teams collected provided a basis for calculating how many dead birds were likely missed by search teams during the actual Cosco Busan oil spill. This study determined that a two-person search team would find 68% of the dead bird carcasses on San Francisco Bay beaches.

More than a dozen other studies [PDF] were also performed after this oil spill, contributing additional data that went into the calculations of the total numbers and species of birds killed. Through this work, the actual number of birds killed by the spill was estimated to be 6,849, nearly two and a half times the number of birds actually collected during the Cosco Busan oil spill.

We commonly use several other methods to determine the magnitude of an oil spill’s effects on animals and plants, including studies of habitat changes, laboratory toxicity studies, and modeling.

Stay tuned because we plan to discuss these approaches more in-depth in the future. In the meantime, learn about the scientific processes we use to assess an oil spill’s environmental impacts at darrp.noaa.gov/science/our-scientific-process.


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Births Down and Deaths Up in Gulf Dolphins Affected by Deepwater Horizon Oil Spill

A mother bottlenose dolphin pushes her dead newborn calf at the water's surface.

Dolphin Y01 pushes a dead calf through the waters of Barataria Bay, Louisiana, in March 2013. This behavior is sometimes observed in female dolphins when their newborn calf does not survive. Barataria Bay dolphins have seen a disturbingly low rate of reproductive success in the wake of the Deepwater Horizon oil spill. (Louisiana Department of Wildlife and Fisheries)

In August of 2011, a team of independent and government scientists evaluating the health of bottlenose dolphins in Louisiana’s Barataria Bay gave dolphin Y35 a good health outlook.

Based on the ultrasound, she was in the early stages of pregnancy, but unlike many of the other dolphins examined that summer day, Y35 was in pretty good shape. She wasn’t extremely underweight or suffering from moderate-to-severe lung disease, conditions connected to exposure to Deepwater Horizon oil in the heavily impacted Barataria Bay.

Veterinarians did note, however, that she had alarmingly low levels of important stress hormones responsible for behaviors such as the fight-or-flight response. Normal levels of these hormones help animals cope with stressful situations. This rare condition—known as hypoadrenocorticism—had never been reported before in dolphins, which is why it was not used for Y35 and the other dolphins’ health prognoses.

Less than six months later, researchers spotted Y35 for the last time. It was only 16 days before her expected due date. She and her calf are now both presumed dead, a disturbingly common trend among the bottlenose dolphins that call Barataria Bay their year-round home.

This trend of reproductive failure and death in Gulf dolphins over five years of monitoring after the 2010 Deepwater Horizon oil spill is outlined in a November 2015 study led by NOAA and published in the peer-reviewed journal Proceedings of the Royal Society.

Of the 10 Barataria Bay dolphins confirmed to be pregnant during the 2011 health assessment, only two successfully gave birth to calves that have survived. This unusually low rate of reproductive success—only 20%—stands in contrast to the 83% success rate in the generally healthier dolphins being studied in Florida’s Sarasota Bay, an area not affected by Deepwater Horizon oil.

Baby Bump in Failed Pregnancies

While hypoadrenocorticism had not been documented previously in dolphins, it has been found in humans. In human mothers with this condition, pregnancy and birth—stressful and risky enough conditions on their own—can be life-threatening for both mother and child when the condition is left untreated. Wild dolphins with this condition would be in a similar situation.

Mink exposed to oil in an experiment ended up exhibiting very low levels of stress hormones, while sea otters exposed to the Exxon Valdez oil spill experienced high rates of failed pregnancies and pup death. These cases are akin to what scientists have observed in the dolphins of Barataria Bay after the Deepwater Horizon oil spill.

Among the pregnant dolphins being monitored in this study, at least two lost their calves before giving birth. Veterinarians confirmed with ultrasound that one of these dolphins, Y31, was carrying a dead calf in utero during her 2011 exam. Another pregnant dolphin, Y01, did not successfully give birth in 2012, and was then seen pushing a dead newborn calf in 2013. Given that dolphins have a gestation of over 12 months, this means Y01 had two failed pregnancies in a row.

The other five dolphins to lose their calves after the Deepwater Horizon oil spill, excluding Y35, survived pregnancy themselves but were seen again and again in the months after their due dates without any young. Dolphin calves stick close to their mothers’ sides in the first two or three months after birth, indicating that these pregnant dolphins also had calves that did not survive.

At least half of the dolphins with failed pregnancies also suffered from moderate-to-severe lung disease, a symptom associated with exposure to petroleum products. The only two dolphins to give birth to healthy calves had relatively minor lung conditions.

Survival of the Least Oiled

Dolphin Y35 wasn’t the only one of the 32 dolphins being monitored in Barataria Bay to disappear in the months following her 2011 examination. Three others were never sighted again in the 15 straight surveys tracking these dolphins. Or rather, they were never seen again alive. One of them, Y12, was a 16-year-old adult male whose emaciated carcass washed up in Louisiana only a few weeks before the pregnant Y35 was last seen. In fact, the number of dolphins washing up dead in Barataria Bay from August 2010 through 2011 was the highest ever recorded for that area.

Survival rate in this group of dolphins was estimated at only 86%, down from the 95-96% survival seen in dolphin populations not in contact with Deepwater Horizon oil. The marshy maze of Barataria Bay falls squarely inside the footprint of the Deepwater Horizon oil spill, and its dolphins and others along the northern Gulf Coast have repeatedly been found to be sick and dying in historically high numbers. Considering how deadly this oil spill has been for Gulf bottlenose dolphins and their young, researchers expect recovery for these marine mammals to be a long time coming.

Watch an updated video of the researchers as they temporarily catch and give health exams to some of the dolphins in Barataria Bay, Louisiana, in August of 2011 and read a 2013 Q&A with two of the NOAA researchers involved in these studies:

This study was conducted under the Natural Resource Damage Assessment for the Deepwater Horizon oil spill. These results are included in the injury assessment documented in the Draft Programmatic Assessment and Restoration Plan that is currently out for public comment. We will accept comments on the plan through December 4, 2015.

This research was conducted under the authority of Scientific Research Permit nos. 779-1633 and 932-1905/MA-009526 issued by NOAA’s National Marine Fisheries Service pursuant to the U.S. Marine Mammal Protection Act.


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What Happens When Oil Spills Meet Massive Islands of Seaweed?

Floating bits of brown seaweed at ocean surface

Floating rafts of sargassum, a large brown seaweed, can stretch for miles across the ocean. (Credit: Sean Nash/Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

The young loggerhead sea turtle, its ridged shell only a few inches across, is perched calmly among the floating islands of large brown seaweed, known as sargassum. Casually, it nibbles on the leaf-like blades of the seaweed, startling a nearby crab. Open ocean stretches for miles around these large free-floating seaweed mats where myriad creatures make their home.

Suddenly, a shadow passes overhead. A hungry seabird?

Taking no chances, the small sea turtle dips beneath the ocean surface. It dives through the yellow-brown sargassum with its tangle of branches and bladders filled with air, keeping everything afloat.

Home Sweet Sargassum

This little turtle isn’t alone in seeking safety and food in these buoyant mazes of seaweed. Perhaps nowhere is this more obvious than a dynamic stretch of the Atlantic Ocean off the East Coast of North America named for this seaweed: the Sargasso Sea. Sargassum is also an important part of the Gulf of Mexico, which contains the second most productive sargassum ecosystem in the world.

Some shrimp, crabs, and fish are specially suited to life in sargassum. Certain species of eel, fish, and shark spawn there. Each year, humpback whales, tuna, and seabirds migrate across these fruitful waters, taking advantage of the gathering of life that occurs where ocean currents converge.

Cutaway graphic of ocean with healthy sargassum seaweed habitat supporting marine life.

Illustration of sargassum and associated marine life, including fish, sea turtles, birds, and marine mammals. Sargassum is a brown algae that forms a unique and highly productive floating ecosystem on the surface of the open ocean. (NOAA) Click to enlarge.

The Wide and Oily Sargasso Sea

However, an abundance of marine life isn’t the only other thing that can accumulate with these large patches of sargassum. Spilled oil, carried by currents, can also end up swirling among the seaweed.

If an oil spill made its way somewhere like the Sargasso Sea, a young sea turtle would encounter a much different scene. As the ocean currents brought the spill into contact with sargassum, oil would coat those same snarled branches and bladders of the seaweed. The turtles and other marine life living within and near the oiled sargassum would come into contact with the oil too, as they dove, swam, and rested among the floating mats.

That oil can be inhaled as vapors, be swallowed or consumed with food, and foul feathers, skin, scales, shell, and fur, which in turn smothers, suffocates, or strips the animal of its ability to stay insulated. The effects can be toxic and deadly.

Cutaway graphic of ocean with potential impacts of oil on sargassum seaweed habitat and marine life.

Illustration of the potential impacts of an oil spill on sargassum and associated marine life in the water column. (NOAA) Click to enlarge.

While sea turtles, for example, as cold-blooded reptiles, may enjoy the relatively warmer waters of sargassum islands, a hot sun beating down on an oiled ocean surface can raise water temperatures to extreme levels. What starts as soothing can soon become stressful.

Depending on how much oil arrived, the sargassum would grow less, or not at all, or even die. These floating seaweed oases begin shrinking. Where will young sea turtles take cover as they cross the unforgiving open ocean?

As life in the sargassum starts to perish, it may drop to the ocean bottom, potentially bringing oil and the toxic effects with it. Microbes in the water may munch on the oil and decompose the dead marine life, but this can lead to ocean oxygen dropping to critical levels and causing further harm in the area.

From Pollution to Protection

Young sea turtles swims through floating seaweed mats.

The floating habitat that sargassum creates provides food, refuge, and breeding grounds for an array of marine species, including sea turtles. (NOAA)

NOAA and the U.S. Fish and Wildlife Service have designated sargassum as a critical habitat for threatened loggerhead sea turtles.

Sargassum has also been designated as Essential Fish Habitat by Gulf of Mexico Fishery Management Council and National Marine Fisheries Service since it also provides nursery habitat for many important fishery species (e.g., dolphinfish, triggerfishes, tripletail, billfishes, tunas, and amberjacks) and for ecologically important forage fish species (e.g., butterfishes and flyingfishes).

Sargassum and its inhabitants are particularly vulnerable to threats such as oil spills and marine debris due to the fact that ocean currents naturally tend to concentrate all of these things together in the same places. In turn, this concentrating effect can lead to marine life being exposed to oil and other pollutants for more extended periods of time and perhaps greater impacts.

However, protecting sargassum habitat isn’t impossible and it isn’t out of reach for most people. Some of the same things you might do to lower your impact on the planet—using less plastic, reducing your demand for oil, properly disposing of trash, discussing these issues with elected officials—can lead to fewer oil spills and less trash turning these magnificent islands of sargassum into floating islands of pollution.

And maybe protect a baby sea turtle or two along the way.