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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Accidents on a Flooded Lower Mississippi River Keep NOAA Busy with a Rash of Spills

Damaged barge on the Mississippi River.

A barge carrying slurry oil being pushed by the towing vessel Amy Francis hit the Natchez-Vidalia Bridge, Jan. 21, 2016. The barge reportedly has a maximum potential of more than 1 million gallons of slurry oil on board. (U.S. Coast Guard)

This is a post by the Office of Response and Restoration’s Donna Roberts.

Did you know that oil spills occur every day in U.S. waters? Rivers bustling with ship traffic, such as the Mississippi, are no exception to this rule.

In the past few weeks, we’ve been involved with quite a few accidents involving vessels carrying oil and chemicals on the Lower Mississippi River.

These river accidents coincided with high water and swift currents. Despite safeguards for vessel traffic put in place by the U.S. Coast Guard, the river conditions resulted in ships colliding, hitting bridges and ground, and breaking away from their towing vessels. One unlucky railroad bridge in Vicksburg, Mississippi, has been hit by vessels five times already this year.

Even now, the NOAA River Forecast Center reports that the Lower Mississippi is experiencing moderate flood conditions. It’s difficult to navigate a river with a tow of barges at any flow—and extremely challenging when the flow is high and fast. In spite of everyone’s best efforts, under conditions like these, accidents can and do still happen, and investigations are ongoing into the precise causes.

Luckily, most of the incidents that have occurred were relatively minor, resulted in no injuries to vessel crews, and all spills received immediate responses from state and federal agencies. Still, when oil or chemicals spill into rivers, we know that they differ from spills in the ocean or along coasts, and therefore present different challenges for spill responders.

Here are just a few of the dozen or so spills and near-spills we know of and which have been keeping our spill modelers, chemists, and Scientific Support Coordinators busy over the past few weeks.

January 21, 2016: A barge being towed by the UTV Amy Frances struck the Natchez Bridge, where Highway 84 crosses over the Lower Mississippi River between Mississippi and Louisiana, in the vicinity of Mile Marker 363. As a result, two of the barge’s tanks were damaged, spilling slurry oil, which our chemical lab confirmed was denser than water. That means this oil sinks.

In the wake of this oil spill, one of our Scientific Support Coordinators helped survey the river to detect sunken oil. Given the river’s very fast and turbulent water at the time, we think any oil released from the damaged tanks was immediately broken into small droplets and carried downstream while also sinking below the river surface. Any oil that reached the bottom was probably mixed with or buried by the sand moving downstream near the river bottom. This is because rivers that move a lot of water also move a lot of sediment.

In addition, we provided information on the expected fate and effects of the barge’s spilled slurry oil and on the animals and habitats that could be at risk.

Workers on a river edge pump oil from a damaged barge.

Response crews remove oil from the damaged MM-46 barge, Jan. 23, 2016, on the Mississippi River. Crews estimate that approximately 76,000 gallons of clarified oil mixture is still unaccounted for. Crews continue to take soundings of the damaged barge tank to determine the amount spilled while assessment teams work to locate missing product. (U.S. Coast Guard)

January 25, 2016: Just a few days later, the Coast Guard called on us for advice related to a barge containing liquid urea ammonium nitrate (liquid fertilizer), which sank south of Valewood, Mississippi, at Mile Marker 501 on the Mississippi River. Side-scan sonar indicates the barge is upside-down on the river bottom, approximately 80 feet down.

Given the position and water pressure, we believe the chemical cargo stored on the barge was likely released into the river. The chemical is heavier than water and will mix quickly into the water column. Because elevated levels of ammonia can affect aquatic life, our focus was on predicting and tracking where the chemical would go downriver and what would happen to it. Salvage efforts for the barge itself continue.

January 26, 2016: The next day, two vessel tows collided upriver of New Orleans, Louisiana, near Mile Marker 130 on the Lower Mississippi River. The collision capsized one of two barges carrying caustic soda, or sodium hydroxide. We provided the Coast Guard with an initial chemical hazard assessment for this chemical, which is a strong base. The release of a large enough quantity of sodium hydroxide could raise the pH of the water around it, posing a risk to local fish and other aquatic life nearby. The barge is secure, but righting it is difficult in the swift currents. No pollution release has been reported to date.

Science for Spills of All Kinds

During these kinds of spills, we have to be ready to provide the same round-the-clock, science-based support to the Coast Guard and other agencies as big spills like the Deepwater Horizon in the Gulf of Mexico.

For example, if a chemical has spilled into a river, we need to know where it’s going to go, what’s going to happen to it, and what, if any, species will be harmed by it. To help answer the “where’s it going?” question, our response specialists use the spill trajectory tool, GNOME, to predict the possible route the pollutant might follow.

To better understand the pollutant and its possible effects, we use software tools such as CAMEO Chemicals to provide information about the chemical’s properties, toxicity, and behavior as it is diluted by the river water. Our Chemical Aquatic Fate and Effects (CAFE) database contains information on the effects of thousands of chemicals, oils, and dispersants on aquatic life.

The Mississippi River and its floodplain are home to a diverse population of living things. On the Lower Mississippi, there may be as many as 60 separate species of mussel. To protect vulnerable species, we use our Environmental Sensitivity Index maps and data to report what animals or habitats could be at risk, particularly those that are threatened or endangered. Keeping responders and the public safe and minimizing environmental harm are two of our top priorities during any spill, no matter the size.

Donna Roberts

Donna Roberts

Donna Roberts is a writer for the Emergency Response Division of NOAA’s Office of Response and Restoration (OR&R). Her work supports the OR&R website and the Environmental Sensitivity Index mapping program.


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Apply Now for NOAA’s First Class Examining the Science of Chemical Spills

People standing in a lab next to chemical testing equipment.

This three and a half day class will provide a broad, science-based approach to understanding chemical release response. (NOAA)

For years, NOAA’s Office of Response and Restoration has been offering our popular Science of Oil Spills classes to oil spill responders and planners. But oil isn’t the only hazardous material for which we have expertise. This March, we’ll launch our first official Science of Chemical Releases (SOCR) class to share this expertise in new ways.

This class is designed to help spill responders and planners increase their scientific understanding when preparing for and analyzing chemical spills, which could range from toluene to sulfuric acid, and when making risk-based decisions to protect public health, safety, and the environment in the event of such a release.

The three and a half day class will take place at NOAA’s Gulf of Mexico Disaster Response Center in Mobile, Alabama, from March 21–24, 2016.

We are accepting applications for this class until Friday, February 19, 2016. We will notify accepted participants by email no later than Friday, February 26.

The class is primarily intended for new and mid-level spill responders, planners, and stakeholders from all levels of government, industry, and academia.

During the class, participants will be introduced to a realistic scenario to demonstrate the use of scientific tools, resources, and knowledge to aid in response to chemical releases. The scenario will be centered on a hypothetical chemical incident involving the derailment of multiple railcars containing hazardous chemicals, resulting in a fire and release of dangerous chemicals into the environment.

Through this new training, we hope to provide a broad, science-based approach to understanding chemical release response, thereby increasing awareness and preparedness and reducing uncertainty and risk associated with this type of incident.

There is no tuition for this class. However, students are responsible for all miscellaneous expenses, including lodging, travel, and food.

For more information, and to learn how to apply for the class, visit the SOCR Classes page.

If you have any questions or experience any problems with your application, please send us an email.

To receive updates about our activities and events, including Science of Chemical Releases or Science of Oil Spills classes, subscribe to our monthly newsletter.


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Science of Oil Spills Training: Apply for Summer 2016

Group of Coast Guard members sit and stand at a table.

These trainings help new and mid-level spill responders increase their understanding of oil spill science when analyzing spills and making risk-based decisions. (NOAA)

NOAA‘s Office of Response and Restoration, a leader in providing scientific information in response to marine pollution, has scheduled a summer Science of Oil Spills (SOS) class in Seattle, Washington, June 6-10, 2016.

Currently, we are accepting applications for three SOS classes for these locations and dates:

  • Mobile, Alabama, the week of March 28, 2016
  • Ann Arbor, Michigan, the week of May 16, 2016
  • Seattle, Washington, the week of June 6, 2016

We will accept applications for these classes as follows:

  • For the Mobile class, the application period will be open until Friday, January 22. We will notify accepted participants by email no later than Friday, February 5.
  • For the Ann Arbor class, the application period will be open until Friday, March 11. We will notify accepted participants by email no later than Friday, March 25.
  • For the Seattle class, the application period will be open until Friday, April 1. We will notify accepted participants by email no later than Friday, April 15.

SOS classes help spill responders increase their understanding of oil spill science when analyzing spills and making risk-based decisions. They are designed for new and mid-level spill responders.

The trainings cover:

  • Fate and behavior of oil spilled in the environment.
  • An introduction to oil chemistry and toxicity.
  • A review of basic spill response options for open water and shorelines.
  • Spill case studies.
  • Principles of ecological risk assessment.
  • A field trip.
  • An introduction to damage assessment techniques.
  • Determining cleanup endpoints.

To view the topics for the next SOS class, download a sample agenda [PDF, 170 KB].

Please understand that classes are not filled on a first-come, first-served basis. We try to diversify the participant composition to ensure a variety of perspectives and experiences, to enrich the workshop for the benefit of all participants. Classes are generally limited to 40 participants.

For more information, and to learn how to apply for the class, visit the SOS Classes page.


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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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Our Top 10 New Year’s Resolutions for 2016

2015 written on a sandy beach with an approaching wave.

So long, 2015. Hello, 2016!

Another year has gone by, and we’ve stayed plenty busy: responding to a leaking California pipeline, examining the issue of wrecked and abandoned ships, preparing a natural resource damage assessment and restoration plan for the Gulf of Mexico, and removing 32,201 pounds of marine debris from Hawaii’s Midway Atoll.

You can read more about what we accomplished in the last year, but keep in mind we have big goals for 2016 too. We’re aiming to:

  1. Be better models. This spring, we are planning to release an overhaul of our signature oil spill trajectory forecasting (GNOME) and oil weathering (ADIOS) models, which will be combined into one tool and available via an online interface for the first time.
  2. Tidy up. Our coasts, that is. In the next year, we will oversee marine debris removal projects in 17 states and territories, empowering groups to clean up coastal areas of everything from plastics to abandoned fishing gear.
  3. Use or lose. Nature and wildlife offer a lot of benefits to people, and we make use of them in a number of ways, ranging from recreational fishing to birdwatching to deep-seated cultural beliefs. In 2016 we’ll examine what we lose when nature and wildlife get harmed from pollution and how we calculate and make up for those losses.
  4. Get real. About plastic in the ocean, that is. We’ll be turning our eye toward the issue of plastic in the ocean, how it gets there, what its effects are, and what we can do to keep it out of the ocean.
  5. Explore more. We’ll be releasing an expanded, national version of our DIVER data management tool, which currently holds only Deepwater Horizon data for the Gulf of Mexico, allowing us and our partners to better explore and analyze ocean and coastal data from around the country.
  6. Get artistic. Through our NOAA Marine Debris Program, we are funding projects to create art from ocean trash to raise awareness of the issue and keep marine debris off our coasts and out of our ocean.
  7. Break ground on restoration. Finalizing the draft comprehensive restoration plan for the Gulf of Mexico, following the 2010 Deepwater Horizon oil spill, will bring us one step closer to breaking ground on many restoration projects over the next several years.
  8. App to it. We are working on turning CAMEO Chemicals, our popular database of hazardous chemicals, into an application (app) for mobile devices, making access to critical information about thousands of potentially dangerous chemicals easier than ever.
  9. Train up. We pride ourselves on providing top-notch training opportunities, and in 2016, we already have Science of Oil Spill classes planned in Mobile, Alabama, and Ann Arbor, Michigan (with more to come). Plus, we’ve introduced a brand-new Science of Chemical Releases class, designed to provide information and tools to better manage and plan for responses to chemical incidents.
  10. Get strategic. We are updating our five year strategic plan, aligning it with NOAA’s Ocean Service strategic priorities [PDF], which are coastal resilience (preparedness, response, and recovery), coastal intelligence, and place-based conservation.


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How Will Climate Change, New Technologies, and Shifting Trade Patterns Affect Global Shipping?

Large waves crash on a huge cargo ship aground on a beach.

After a major storm, a massive bulk cargo ship, the Pasha Bulker, ran aground on a beach in Australia in 2007. (Credit: Tim J. Keegan/Creative Commons Attribution-Share Alike 2.0 Generic license)

This is a guest post by University of Washington graduate students Megan Desillier, Seth Sivinski, and Nicole White.

A warming climate is opening up new shipping routes through the Arctic Ocean as summer sea ice shrinks. Developing technologies allow mega-ships unprecedented in size and cargo to take to the seas. North America is increasingly exporting oil, shifting global trade patterns.

Each of these issues poses a suite of potential challenges for safely shipping commodities across the ocean and around the world. Out of these challenges, new risks are emerging in marine transportation that NOAA and the maritime industry need to consider.

Our group of three graduate students at the University of Washington, with the support of the International Tanker Owners Pollution Federation (ITOPF) and NOAA’s Office of Response and Restoration, are looking to understand how the world’s shipping dynamic has changed in recent years and how these emerging challenges in marine transportation will affect that dynamic. And then we aim to answer: how should NOAA and ITOPF best prepare for responding to these new risks?

In the course of this research project, we will attempt to identify and assess significant emerging risks in marine transportation that have the potential to lead to oil or chemical spills. We are focused on three drivers of emerging risks in the global shipping network: developing technologies, changing patterns of marine trade, and shifting environmental conditions due to climate change. Each of these drivers will be considered within three distinct time frames: the present, 4-10 years from now, and more than 10 years from now.

Risky Business

Fishing vessl half in water and half on a damaged building.

Hurricane Katrina’s storm surge left this fishing vessel on top of a local fish dealer shop in Mississippi. Even small changes in sea levels can have major effects on storm surge. How will a changing climate affect affect global shipping? (NOAA)

The emerging risks that we will identify and assess come from analyzing the network of global cargo ship movements, focusing on the emerging usage of the Northern Sea Route, Northwest Passage, Trans-Arctic Route, the Panama Canal, the Suez Canal, and the possibility of a future Nicaraguan Canal.

At this point in our project, we have come across several interesting findings relating to each of our three main research areas. Within the area of developing technology, for example, we are examining the emerging risk of “mega-vessels,” which include “mega-containers,” “mega-tankers,” and “mega-bulkers,” depending on their cargo type. These mega-vessels are massive and measure significantly larger than previous, standard-sized vessels. For example, any container ship over 10,000 twenty-foot equivalent units, or TEUs, can be considered a “mega-ship.” However, the largest mega-vessel to date can handle 18,000 TEUs.

Bulk carriers are used to transport unpackaged cargo in bulk, such as grain, ore, and cement. These ships have also grown in size to the new mega-bulkers, which can handle over 80,000 deadweight tons (DWT), as opposed to the most common, smaller-sized bulk carrier that can handle 60,000 DWTs. In addition, ships are carrying riskier cargoes, which, depending on the cargo, can lead to a dangerous phenomenon known as liquefaction. In general, liquefaction can occur during events like earthquakes, when intense shaking causes “water-saturated sediment temporarily [to lose] strength and [act] as a fluid.”

This phenomenon can also happen on board ships when a cargo, like nickel-ore, becomes wet either before being loaded or while on board and then liquefies due to the ship’s movements. When that happens, the liquefied cargo quickly destabilizes the ship and can lead to it sinking. There are numerous cases of cargo liquefaction occurring on standard-sized bulk carrier ships, which can result in the loss of both crew and vessel.

Context Clues

We also have incorporated several elements to give social-economic, technological, and environmental context to our research of emerging maritime risks. The social-economic element considers the form of cargoes being shipped, environmental resources potentially affected by pollution, available industry tools, and the types of vessels involved.

As for the technical element, we’ll focus on understanding the gap in the salvage of mega-vessels and vessels in the Arctic region, the increased use of floating production storage and offloading vessels (FPSOs, which act like semi-mobile floating fuel storage tanks), risks from vessel automation technologies, and finally, the increased congestion of ships in high-risk areas and choke points, such as the narrow Bering Strait between Alaska and Russia.

For the environmental context, we’ll examine changing environmental conditions that may present additional risks to marine transportation, such as the increased intensity and frequency of storms, sea level rise, and Arctic sea ice melt.

We’ll also consider some market drivers, such as the North American oil trade and the International Maritime Organization’s Polar Code (which is an international shipping safety code for polar waters), in a broad global context. However, our research will not directly consider organizational, regulatory, and market contextual elements in any significant detail.

Relevance and Risk

After we analyze and categorize potential risks, we’ll consider the materiality, or relevance, of our identified risks and the types of incidents that could result. We’ll be connecting how important our identified risks are to the potential losses and damages to vessels, cargoes, and the environment resulting from specific types of incidents. For example, if larger ships are carrying larger quantities of oil as fuel or cargo, then damage to a ship’s hull could spill more oil and result in greater potential environmental impacts.

Stay tuned for updates on our research over the next few months.

Megan Desillier, Seth Sivinski, and Nicole White are Master’s Candidates at the University of Washington (UW) in the School of Marine and Environmental Affairs working with faculty advisors Robert Pavia and Thomas M. Leschine. The team is researching emerging risks in marine transportation for the International Tanker Owner Pollution Federation (ITOPF) and is being provided additional assistance in their research from the National Oceanic and Atmospheric Administration (NOAA). The students are completing this research over the course of an academic year as part of the thesis/capstone requirement for the School of Marine and Environmental Affairs at the UW. Our team would like to thank our sponsor, ITOPF, as well as NOAA for providing additional assistance. To contact the authors, please email Robert Pavia at bobpavia@uw.edu.

The views expressed in this post reflect those of the authors and do not necessarily reflect the official views of NOAA or the U.S. federal government.

Photo of Pasha Bulker courtesy of Tim J. Keegan and used under Creative Commons Attribution-Share Alike 2.0 Generic license.


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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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