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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This Is How We Help Make the Ocean a Better Place for Coral

Large corals on the seafloor.

The ocean on its own is an amazing place. Which is why we humans like to explore it, from its warm, sandy beaches to its dark, mysterious depths. But when humans are involved, things can and often do go wrong.

That’s where we come in. Our corner of NOAA helps figure out what impacts have happened and what restoration is needed to make up for them when humans create a mess of the ocean, from oil spills to ship groundings.

In honor of World Ocean Day, here are a few ways we at NOAA make the ocean a better place for corals when ships accidentally turn them into undersea roadkill.

First, we literally vacuum up broken coral and rubble from the seafloor after ships run into and get stuck on coral reefs. The ships end up crushing corals’ calcium carbonate homes, often carpeting the seafloor with rubble that needs to be removed for three reasons.

  1. To prevent it from smashing into healthy coral nearby.
  2. To clear space for re-attaching coral during restoration.
  3. To allow for tiny, free-floating coral babies to settle in the cleared area and start growing.

Check it out:A SCUBA diver using a suction tube to vacuum coral rubble from the seafloor during coral restoration after the VogeTrader ship grounding.Sometimes, however, the broken bits get stuck in the suction tube, and you have to give it a good shake to get things moving. SCUBA divers shaking a suction tube to clear it on the seafloor.Next, we save as many dislodged and knocked over corals as we can. In this case, popping them into a giant underwater basket that a boat pulls to the final restoration site.

SCUBA diver placing coral piece into a large wire basket on the seafloor during coral restoration after the VogeTrader ship grounding.Sometimes we use “coral nurseries” to regrow corals to replace the ones that were damaged. This is what that can look like:

Staghorn coral fragments hanging on an underwater tree structure of PVC pipes.Then, we cement healthy corals to the seafloor, but first we have to prepare the area, which includes scrubbing a spot for the cement and coral to stick to.

SCUBA diver scrubbing a spot on the seafloor for the cement and coral to stick to.(And if that doesn’t work very well, we’ll bring out a power washer to get the job done.)

SCUBA diver using a power washer to clear a spot on the seafloor for the cement and coral to stick to during coral restoration after the VogeTrader ship grounding.Finally, we’re ready for the bucket of cement and the healthy coral.

SCUBA diver turning over a bucket of cement on the seafloor during coral restoration after the VogeTrader ship grounding.

Instead of cement, we may also use epoxy, nails, or cable ties to secure corals to the ocean floor.

After all that work, the seafloor goes from looking like this:

View of seafloor devoid of coral before restoration.To this:

View of seafloor covered with healthy young coral and fish after restoration due to the VogeTrader grounding.

Ta-da! Good as new, or at least, on its way back to being good-as-new.

When that’s not enough to make up for all the harm done to coral reefs hit by ships, we look for other restoration projects to help corals in the area, like this project to vacuum invasive algae off of coral reefs in Oahu.

Watch how this device, dubbed the “Super Sucker,” works to efficiently remove the yellow-brown algae that is smothering the corals:

Or, as another example of a coral restoration project, we set sail each year to the remote Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands to pull more than 50 tons of giant, abandoned fishing nets off of the pristine coral reefs.

In 2014, that included removing an 11 ton “monster net” from a reef:

For the most part, the coral restoration you’ve seen here was completed by NOAA and our partners, beginning in October 2013 and wrapping up in April 2014.

These corals were damaged off the Hawaiian island of Oahu in February of 2010 when the cargo ship M/V VogeTrader ran aground and was later removed from a coral reef in Kalaeloa/Barber’s Point Harbor.


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Who Thinks Crude Oil Is Delicious? These Ocean Microbes Do

This is a post by Dalina Thrift-Viveros, a chemist with NOAA’s Office of Response and Restoration.

Edge of oil slick at ocean surface.

There are at least seven species of ocean bacteria that can survive by eating oil and nothing else. However, usually only a small number of oil-eating bacteria live in any given part of the ocean, and it takes a few days for their population to increase to take advantage of their abundant new food source during an oil spill. (NOAA)

Would you look at crude oil and think, “Mmm, tasty…”? Probably not.

But if you were a microbe living in the ocean you might have a different answer. There are species of marine bacteria in several families, including Marinobacter, Oceanospiralles, Pseudomonas, and Alkanivorax, that can eat compounds from petroleum as part of their diet. In fact, there are at least seven species of bacteria that can survive solely on oil [1].

These bacteria are nature’s way of removing oil that ends up in the ocean, whether the oil is there because of oil spills or natural oil seeps. Those of us in the oil spill response community call this biological process of removing oil “biodegradation.”

What Whets Their Oily Appetites?

Communities of oil-eating bacteria are naturally present throughout the world’s oceans, in places as different as the warm waters of the Persian Gulf [2] and the Arctic conditions of the Chukchi Sea north of Alaska [3].

Each community of bacteria is specially adapted for the environment where it is living, and studies have found that bacteria consume oil most quickly when they are kept in conditions similar to their natural environments [4]. So that means that if you took Arctic bacteria and brought them to an oil spill in the Gulf of Mexico, they would not eat the oil as quickly as the bacteria that are already living in the Gulf. You would get the same result in the reverse case, with the Arctic bacteria beating out the Gulf bacteria at an oil spill in Alaska.

Other factors that affect how quickly bacteria degrade oil include the amount of oxygen and nutrients in the water, the temperature of the water, the surface area of the oil, and the kind of oil that they are eating [4][5][6]. That means the bacteria that live in a given area will consume the oil from a spill in the summer more quickly than a spill in the winter, and will eat light petroleum products such as gasoline or diesel much more quickly than heavy petroleum products like fuel oil or heavy crude oil.

Oil-eating microbes fluorescing in a petri dish.

This bacteria, fluorescing under ultraviolet light in a petri dish, is Pseudomonas aeruginosa. It has been used during oil spills to break down the components of oil. (Credit: Wikimedia user Sun14916/Creative Commons Attribution-ShareAlike 3.0 Unported license)

Asphalt, the very heaviest component of crude oil, is actually so difficult for bacteria to eat that we can use it to pave our roads without worrying about the road rotting away.

What About During Oil Spills?

People are often interested in the possibility of using bacteria to help clean up oil spills, and most oil left in the ocean long enough is consumed by bacteria.

However, most oil spills last only a few days, and during that time other natural “weathering” processes, such as evaporation and wave-induced breakup of the oil, have a much bigger effect on the appearance and location of the oil than bacteria do. This is because there are usually only a small number of oil-eating bacteria in any given part of the ocean, and it takes a few days for their population to increase to take advantage of their abundant new food source.

Because of this lag time, biodegradation was not originally included in NOAA’s oil weathering software ADIOS. ADIOS is a computer model designed to help oil spill responders by predicting how much of the oil will stay in the ocean during the first five days of a spill.

However, oil spills like the 2010 Deepwater Horizon well blowout, which released oil for about three months, demonstrate that there is a need for a model that can tell us what would happen to the oil over longer periods of time. My team in the Emergency Response Division at NOAA’s Office of Response and Restoration has recognized that. As a result, version 3 of ADIOS, due to be released later in 2015, will take into account biodegradation.

My team and I used data published in scientific journals on the speed of oil biodegradation under different conditions to develop an equation that can predict how fast the components of oil will be consumed, and how the speed of this process can change based on the surface area-to-mass ratio of the oil and the climate it is in. A report describing the technical details of the model will be published in the upcoming Proceedings of the Arctic and Marine Oilspill Program Technical Seminar, which will be released after the June conference.

Including oil biodegradation in our ADIOS software will provide oil spill responders with an even better tool to help them make decisions about their options during a response. As part of the team working on this project, it has provided me with a much greater appreciation for the important role that oil-eating bacteria play in the long-term effort to keep our oceans free of oil.

I know I’m certainly glad they think oil is delicious.

Dalina Thrift-ViverosDalina Thrift-Viveros is a Seattle-based chemist who has been providing chemistry expertise for Emergency Response Division software projects and spill responders since 2011, when she first started working with NOAA and Genwest. When she is not involved in chemistry-related activities, Dalina sings with the rock band Whiskey River and plays sax with her jazz group, The Paul Engstrom Trio.

Literature cited

[1] Yakimov, M.M., K.N. Timmis, and P.N. Golyshin. “Obligate oil-degrading marine bacteria,” Current Opinion in Biotechnology, 2007, 18(3), pp. 257-266.

[2] Hassanshahian, M., G. Emtiazi, and S.Cappello. “Isolation and characterization of crude-oil-degrading bacteria from the Persian Gulf and the Caspian Sea,” Marine Pollution Bulletin, 2012, 64, pp. 7–12.

[3] McFarlin, K.M., R.C. Prince, R. Perkins, and M.B. Leigh. “Biodegradation of Dispersed Oil in Arctic Seawater at -1°C,” PLoS ONE, 2014, 9:e84297, pp. 1-8.

[4] Atlas, R.M. “Petroleum Biodegradation and Oil Spill Bioremediation,” Marine Pollution Bulletin, 1995, 31, pp. 178-182.

[5] Atlas, R.M. and T.C. Hazen. “Oil Biodegradation and Bioremediation: A Tale of the Two Worst Spills in U.S. History,” Environmental Science & Technology, 2011, 45, pp. 6709-6715.

[6] Head, I.M., D.M. Jones, and W.F.M. Röling, “Marine microorganisms make a meal of oil,” Nature Reviews Microbiology, 2006, 4, pp. 173-182.


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NOAA and Partners Work Quickly to Save Corals Hit by Catamaran in Puerto Rico

Experts estimate that thousands of corals were broken, dislodged, buried, or destroyed when the 49-foot-long catamaran M/V Aubi ran aground along the north coast of Puerto Rico the night of May 14, 2015.

Traveling from the Dominican Republic to San Juan, Puerto Rico, the recreational boat became grounded on a coral reef, causing significant damage to the reef. As the vessel was being moved, the vessel’s two hulls slowly ground further into the reef, forming mounds of coral and leaving rubble on the ocean bottom. UPDATED 5/27/2015: The area of the vessel’s direct impact is 366 square meters (not quite 4,000 square feet), while partial impact covers more than 1,000 square meters (roughly 10,764 square feet).

On the night of the grounding, responders were immediately concerned about preventing a spill of the fuel on board the Aubi. The fuel had to be removed from the fuel tanks in the aluminum hulls of the catamaran before it was moved off of the coral reefs. By the evening of May 15, approximately 1,500 gallons of fuel had been removed successfully, readying the vessel to be towed from the reef. It was pulled free during high tide the next morning.

The location of the grounding is in a Puerto Rico Marine Reserve, overseen by the Puerto Rico Department of Natural and Environmental Resources.

Crushing News and Rubble Rousers

The species of coral affected by the accident are mostly Diploria, or brain coral, and Acropora palmata, or elkhorn coral. Listed as threatened under the Endangered Species Act, elkhorn coral is one of the most important reef-building corals in the Caribbean. Brain coral, found in the West Atlantic Ocean and the Caribbean, is also an important reef-building coral and is known for its stony, brain-like appearance.

Although there was significant damage to the coral, an oil spill fortunately was prevented. While exposure to oil may kill corals, it more frequently reduces their ability to perform photosynthesis and causes growth or reproductive problems.

A multi-organizational team, which included NOAA, was able to salvage over 800 coral colonies (or fragments of colonies), moving them into deeper water nearby for temporary holding.  About 75 very large colonies of brain coral were righted but unable to be moved because of their size.

Broken brain coral on seafloor.

Brain coral (Diploria) and elkhorn coral (Acropora palmata) represent the majority of the coral species affected by this vessel grounding. (NOAA)

With buckets and by hand, the team filled 50 loads of rubble (approximately nine cubic yards) into open kayaks and small boats to transport them to a deeper underwater site that Puerto Rico Department of Natural Resources had approved for dumping.  All that material, moved in one day, would otherwise likely have washed into the healthy reef adjacent to the damaged one and potentially caused even more harm.

While poor weather has been preventing further work at the grounding site this past week, the team expects to restart work soon. Once that happens, initial estimates are that it will take 10-15 days to reattach the salvaged corals and to secure the rubble most at risk of moving. Stabilizing or removing the remaining rubble and rebuilding the topographic complexity of the flattened seafloor, accomplished using large pieces of rubble, would likely take an additional 10 days.

Both the location and nature of the corals dominating the area make it a very viable location for complete restoration using nursery-grown corals, but the scope and scale would still need to be determined.

Small Boat, Big Impact?

Healthy brain coral on seafloor.

An area of healthy corals near the site of the grounded M/V Aubi. Divers acted quickly to protect these corals from being damaged by the large amounts of rubble loose on the seafloor after the accident. (NOAA)

Even though the vessel involved in this grounding was relatively small, an unofficial, anecdotal report from the team working on the site noted that the amount of damage appeared comparable to that caused by the groundings of much larger vessels, such as tankers.

If not for the quick work of the U.S. Coast Guard, Puerto Rico Department of Natural Resources, NOAA, support contractors, volunteers from non-governmental organizations, and members of the local community, the damage could have been much worse.

Healthy coral reefs are among the most biologically and economically valuable ecosystems on earth.

According to NOAA’s Coral Reef Conservation Program, a little-known fact is that corals are in fact animals, even though they may exhibit some of the characteristics of plants and are often mistaken for rocks.

Learn more about how NOAA dives to the rescue of corals in the Caribbean when they become damaged by grounded ships.


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NOAA Launches New Data Management Tool for Public Access to Deepwater Horizon Oil Spill Data

Two people launch a water column sampling device off the side of a ship.

Launching a device to take measurements in the water column during the 2010 Deepwater Horizon oil spill. NOAA built the online tool DIVER to organize and provide access to these scientific data and the many others collected in the wake of the spill. (NOAA)

A flexible new data management tool—known as DIVER and developed by NOAA to support the Natural Resource Damage Assessment (NRDA) for the 2010 Deepwater Horizon oil spill—is now available for public use. DIVER stands for “Data Integration, Visualization, Exploration and Reporting,” and it can be accessed at https://dwhdiver.orr.noaa.gov.

DIVER was developed as a digital data warehouse during the Deepwater Horizon oil spill response effort and related damage assessment process, which has required collecting and organizing massive amounts of scientific data on the environmental impacts of the spill.

The tool serves as a centralized data repository that integrates diverse environmental data sets collected from across the Gulf of Mexico ecosystem. It allows scientists from different organizations and laboratories located across the country to upload field data, analyses, photographs, and other key information related to their studies in a standardized format. DIVER thus brings together all of that validated information into a single, web-based tool.

In addition, DIVER provides unprecedented flexibility for filtering and downloading validated data collected as part of the ongoing damage assessment efforts for the Gulf of Mexico. The custom query and mapping interface of the tool, “DIVER Explorer,” provides both a data filter and review tools, which allow users to refine how they look for data and explore large data sets online. Query results are presented in an interactive dashboard, with a map, charts, table of results, metadata (data about the data), and sophisticated options for exporting the data.

View of DIVER Explorer map and query results for environmental impact data in the Gulf of Mexico.

A view of DIVER Explorer query results shown in an interactive dashboard. (NOAA)

In addition to the DIVER Explorer query tools, this website presents a detailed explanation of our data management approach, an explanation of field definitions and codes used in the data warehouse, and a robust help section.

Currently, DIVER provides access to nearly 4 million validated results of analytical chemistry from over 50,000 samples of water, tissue, oil, and sediment collected by federal, state, academic, and nongovernmental organizations to support the Deepwater Horizon damage assessment. As additional data sets become publicly available they will be accessible through the DIVER Explorer tool.

Read the announcement of this tool’s public launch from the NOAA website.


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

The Deepwater Horizon Oil Spill: Five Years Later

This is the third in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

A dolphin is observed with oil on its skin on August 5, 2010, in Barataria Bay, La.

A dolphin is observed with oil on its skin on August 5, 2010, in Barataria Bay, Louisiana. (Louisiana Department of Wildlife and Fisheries/Mandy Tumlin)

Dolphins washing up dead in the northern Gulf of Mexico are not an uncommon phenomenon. What has been uncommon, however, is how many more dead bottlenose dolphins have been observed in coastal waters affected by the Deepwater Horizon oil spill in the five years since. In addition to these alarmingly high numbers, researchers have found that bottlenose dolphins living in those areas are in poor health, plagued by chronic lung disease and failed pregnancies.

Independent and government scientists have undertaken a number of studies to understand how this oil spill may have affected dolphins, observed swimming through oil and with oil on their skin, living in waters along the Gulf Coast. These ongoing efforts have included examining and analyzing dead dolphins stranded on beaches, using photography to monitor living populations, and performing comprehensive health examinations on live dolphins in areas both affected and unaffected by Deepwater Horizon oil.

The results of these rigorous studies, which recently have been and continue to be published in peer-reviewed scientific journals, show that, in the wake of the 2010 Deepwater Horizon oil spill and in the areas hardest hit, the dolphin populations of the northern Gulf of Mexico have been in crisis.

Troubled Waters

Due south of New Orleans, Louisiana, and northwest of the Macondo oil well that gushed millions of barrels of oil for 87 days, lies Barataria Bay. Its boundaries are a complex tangle of inlets and islands, part of the marshy delta where the Mississippi River meets the Gulf of Mexico and year-round home to a group of bottlenose dolphins.

During the Deepwater Horizon oil spill, this area was one of the most heavily oiled along the coast. Beginning the summer after the spill, record numbers of dolphins started stranding, or coming ashore, often dead, in Barataria Bay (Venn-Watson et al. 2015). One period of extremely high numbers of dolphin deaths in Barataria Bay, part of the ongoing, largest and longest-lasting dolphin die-off recorded in the Gulf of Mexico, persisted from August 2010 until December 2011.

In the summer of 2011, researchers also measured the health of dolphins living in Barataria Bay, comparing them with dolphins in Sarasota Bay, Florida, an area untouched by the Deepwater Horizon oil spill. Differences between the two populations were stark. Many Barataria Bay dolphins were in very poor health, some of them significantly underweight and five times more likely to have moderate-to-severe lung disease. Notably, the dolphins of Barataria Bay also were suffering from disturbingly low levels of key stress hormones which could prevent their bodies from responding appropriately to stressful situations. (Schwacke et al. 2014)

“The magnitude of the health effects that we saw was surprising,” said NOAA scientist Dr. Lori Schwacke, who helped lead this study. “We’ve done these health assessments in a number of locations across the southeast U.S. coast and we’ve never seen animals that were in this poor of condition.”

The types of illnesses observed in live Barataria Bay dolphins, which had sufficient opportunities to inhale or ingest oil following the 2010 spill, match those found in people and other animals also exposed to oil. In addition, the levels of other pollutants, such as DDT and PCBs, which previously have been linked to adverse health effects in marine mammals, were much lower in Barataria Bay dolphins than those from the west coast of Florida.

Dead in the Water

Based on findings from the 2011 study, the outlook for dolphins living in one of the most heavily oiled areas of the Gulf was grim. Nearly 20 percent of the Barataria Bay dolphins examined that year were not expected to live, and in fact, the carcass of one of them was found dead less than six months later (Schwacke et al. 2014). Scientists have continued to monitor the dolphins of Barataria Bay to document their health, survival, and success giving birth.

Considering these health conditions, it should come as little surprise that record high numbers of dolphins have been dying along the coasts of Louisiana (especially Barataria Bay), Alabama, and Mississippi. This ongoing, higher-than-usual marine mammal die-off, known as an unusual mortality event, has lasted over four years and claimed more than a thousand marine mammals, mostly bottlenose dolphins. For comparison, the next longest lasting Gulf die-off (in 2005–2006) ended after roughly a year and a half (Litz et al. 2014 [PDF]).

Researchers studying this exceptionally long unusual mortality event, which began in February 2010, identified within it multiple distinct groupings of dolphin deaths. All but one of them occurred after the Deepwater Horizon oil spill, which released oil from April to July 2010, and corresponded with areas exposed heavily to the oil, particularly Barataria Bay (Venn-Watson et al. 2015). In early 2011, the spring following the oil spill, Mississippi and Alabama saw a marked increase in dead dolphin calves, which either died late in pregnancy or soon after birth, and which would have been exposed to oil as they were developing.

The Gulf coasts of Florida and Texas, which received comparatively little oiling from the Deepwater Horizon spill, did not see the same significant annual increases in dead dolphins as the other Gulf states (Venn-Watson et al. 2015). For example, Louisiana sees an average of 20 dead whales and dolphins wash up each year, but in 2011 alone, this state recorded 163 (Litz et al. 2014 [PDF]).

The one grouping of dolphin deaths starting before the spill, from March to May 2010, took place in Louisiana’s Lake Pontchartrain (a brackish lagoon) and western Mississippi. Researchers observed both low salinity levels in this lake and tell-tale skin lesions thought to be associated with low salinity levels on this group of dolphins. This combined evidence supports that short-term, freshwater exposure in addition to cold weather early in 2010 may have been key contributors to those dolphin deaths prior to the Deepwater Horizon spill.

Legacy of a Spill?

A bottlenose dolphin swims in the shallow waters along a sandy beach with orange oil boom.

A bottlenose dolphin swims in the shallow waters along the beach in Grand Isle, Louisiana, near oil containment boom that was deployed on May 28, 2010. Oil from the Deepwater Horizon oil spill began washing up on beaches here one month after the drilling unit exploded. (U.S. Coast Guard)

In the past, large dolphin die-offs in the Gulf of Mexico could usually be tied to short-lived, discrete events, such as morbillivirus and marine biotoxins (resulting from harmful algal blooms). While studies are ongoing, the current evidence does not support that these past causes are responsible for the current increases in dolphin deaths in the northern Gulf since 2010 (Litz et al. 2014).

However, the Deepwater Horizon oil spill—its timing, location, and nature—offers the strongest evidence for explaining why so many dolphins have been sick and dying in the Gulf since 2010. Ongoing studies are assessing disease among dolphins that have died and potential changes in dolphin health over the years since the spill.

As is the case for deep-sea corals, the full effects of this oil spill on the long-lived and slow-to-mature bottlenose dolphins and other dolphins and whales in the Gulf may not appear for years. Find more information related to dolphin health in the Gulf of Mexico on NOAA’s Unusual Mortality Event and Gulf Spill Restoration websites.


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At the Bottom of the Gulf of Mexico, Corals and Diversity Suffered After Deepwater Horizon Oil Spill

The Deepwater Horizon Oil Spill: Five Years Later

This is the second in a series of stories over the coming weeks looking at various topics related to the response, the Natural Resource Damage Assessment science, restoration efforts, and the future of the Gulf of Mexico.

Very little, if any, light from the sun successfully travels to the extreme bottom of the Gulf of Mexico. At these dark depths, the water is cold and the inescapable pressure of thousands of feet of ocean bears down on everything.

Yet life in the deep ocean is incredibly diverse. Here, delicate branches of soft coral are embraced by the curling arms of brittlestars. Slender sea fans, tinged with pink, reach for tiny morsels of food drifting down like snow from above. From minute marine worms to elongated fish, the diversity of the deep ocean is also a hallmark of its health and stability.

However, this picture of health was disrupted on April 20, 2010. Beginning that day and for almost three months after, the Macondo wellhead unleashed an unprecedented amount of oil and natural gas nearly a mile beneath the ocean. In addition, the response to this oil spill released large amounts of chemical dispersant, both at the source of the leaking oil and on the ocean surface. These actions were meant to break down oil that might have threatened life at the sea surface and on Gulf shores. Nevertheless, the implications for the ocean floor were largely unknown at the time.

In the five years since the Deepwater Horizon oil spill, a number of academic and independent scientists along with state and federal agencies, including NOAA and the Bureau of Ocean Energy Management, have been collaborating to study just how this oil spill and response affected the deep ocean and seafloor of the Gulf. What they found was the footprint of the oil spill on the seafloor, stamped on sickened deep-sea corals and out-of-balance communities of tiny marine invertebrates.

A Sickened Seafloor

A part of the world difficult to reach—and therefore difficult to know—the depths of the Gulf of Mexico required a huge collaborative and technological effort to study its inhabitants. Beginning in the fall of 2010, teams of scientists set out on multiple research cruises to collect deep-sea data, armed with specialized equipment, including remotely operated vehicles (ROVs), cameras capable of withstanding the crushing pressure of the deep ocean, and devices that could bore into the ocean bottom and scoop up multiple samples of sediments at a time.

Through these efforts, researchers have uncovered large areas of the Gulf of Mexico seafloor that contain most of the oil spill’s notable deep-sea impacts. One area in particular surrounds the damaged wellhead and stretches to the southwest, following the path of the massive underwater plume of Deepwater Horizon oil. At times, up to 650 feet thick and over a mile wide, the oil plume drifted at depths more than 3,500 feet beneath the ocean surface, leaving traces of its presence on the bottom as it went (Camilli et al. 2010).

The Macondo wellhead sits at the center of a bull’s-eye–shaped pattern of harm on the seafloor, with oil-related impacts lessening in intensity farther from the oil’s source. Further tying this pattern of injury to the Deepwater Horizon spill, a conservative chemical tracer of petroleum turned up in surface seafloor sediments extending 15 miles from the wellhead (Valentine et al. 2014).

Diversity Takes a Nose Dive

Few people ever see the bottom of the deep ocean. So what do these impacted areas actually look like? Starting several months after the leaking well was capped, researchers used ROVs and special cameras to dive down roughly 4,500 feet. They found multiple deep-sea coral colonies showing recent signs of poor health, stress, and tissue damage. On these corals, the polyps, which normally extend frilly tentacles from the corals’ branching arms, were pulled back, and excessive mucus hung from the corals’ skeletons, which also revealed patches of dead tissue. All of these symptoms have been observed in corals experimentally exposed to crude oil (White et al. 2012 PDF).

Five photos of deep-sea coral showing the progression of impacts over several years.

A time series of coral showing the progression of typical impacts at a site of coral colonies located less than seven miles from the source of Deepwater Horizon oil. You can see the brown “floc” material present in November 2010 disappears by March 2011 and afterward, is replaced by fuzzy gray hydroids and the coral loses its brittlestar companion. (Credit: Hsing et al. 2013)

Many of these coral colonies were partly or entirely coated in a clumpy brown material, which researchers referred to as “floc.” Chemical analysis of this material revealed the presence of petroleum droplets with similar chemical markers to Deepwater Horizon oil. The brittlestars usually associated with these corals also appeared in strange colors and positions. Some entire coral colonies were dead.

Research teams noted these observations only at corals within roughly 16 miles of the wellhead (White et al. 2012 PDF, Fisher et al. 2014). However, many similar coral colonies located further from the spill site showed no poor health effects.

Even one and two years later, deep-sea corals within the footprint of the spill still had not recovered. Hydroids took the place of the brown floc material on affected corals. Relatives of jellies, hydroids are fuzzy, grayish marine invertebrates that are known to encrust unhealthy coral.

Life on and under the sediment at the bottom of the Gulf also suffered, with the diversity of a wide range of marine life dropping across an area roughly three times the size of Manhattan (Montagna et al. 2013). Notably, numbers of tiny, pollution-tolerant nematodes increased in areas of moderate impact but at the expense of the number and types of other species, particularly copepods, small crustaceans at the base of the food chain. These effects were related to the concentration of oil compounds in sediments and to the distance from the Deepwater Horizon spill but not to natural oil seeps.

Top row, from left,  two types of crustaceans and a mollusk. Bottom row shows three types of marine worms known as polychaetes.

Examples of some of the common but very small marine invertebrates found living on and under the Gulf of Mexico seafloor. The top row shows, from left, two types of crustaceans and a mollusk, which are more sensitive to pollution. The bottom row shows three types of marine worms known as polychaetes, which tended to dominate ocean sediments with higher oil contamination found near corals. (Courtesy of Paul Montagna, Texas A&M University)

More sensitive to pollution, fewer types and numbers of crustaceans and mollusks were found in sediments around coral colonies showing impacts. Instead, a few types of segmented marine worms known as polychaetes tended to dominate ocean sediments with higher oil contamination near these corals (Fisher et al. 2014).

A Long Time Coming

Life on the bottom of the ocean moves slowly. Deep-sea corals live for hundreds to thousands of years, and their deaths are rare events. Some of the corals coated in oily brown floc are about 600 years old (Prouty et al. 2014). The observed impacts to life in the deep ocean are tied closely to the Deepwater Horizon oil spill, but the full extent of the harm and the eventual recovery may take years, even decades, to manifest (Fisher and Demopoulos, et al. 2014).

Learn more about the studies supported by the federal government’s Natural Resource Damage Assessment for the Deepwater Horizon oil spill, which determines the environmental harm due to the oil spill and response and seeks compensation from those responsible in order to restore the affected resources.


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For Alaska’s Remote Pribilof Islands, a Tale of Survival and Restoration for People and Seals

Set in the middle of Alaska’s Bering Sea, a string of five misty islands known as the Pribilof Islands possess a long, rich, and at times, dark history. A history of near extinction, survival, and restoration for both people and nature. A history involving Alaska Natives, Russians, the U.S. government and military, and seals.

It begins with the native people, known as the Unangan, who live there. They tell a story that, as they say, belongs to a place, not any one person. The story is of the hunter Iggadaagix, who first found these islands many years ago after being swept away in a storm and who wanted to bring the Unangan back there from the Aleutian Islands. When the Unangan finally did return for good, it was in the 18th century, and their lives would become intimately intertwined with those of the northern fur seals (Callorhinus ursinus). Each summer roughly half of all northern fur seals breed and give birth in the Pribilof Islands.

Map of fur seal distributions in Bering Sea and Pacific Ocean, with location of Pribilof Islands.

An 1899 map of the distribution (in red) and migrations of the American and Asiatic Fur Seal Herds in the Bering Sea and North Pacific Ocean. Based on data collected 1893-1897. The Pribilof Islands (St. Paul and St. George) are visible north of the main Aleutian Islands, surrounded by the center collections of red dots. Click to enlarge. (U.S. Government)

But these seals and their luxurious fur, along with the tale of Iggadaagix, would eventually bring about dark times for the seals, the Unangan, and the islands themselves. After hearing of Iggadaagix and searching for a new source of furs, Russian navigator Gavriil Loginovich Pribylov would land in 1786 on the islands which would eventually bear his name. He and others would bring the Unangan from the Aleutian Islands to the Pribilof’s St. George and St. Paul Islands, where they would be put to work harvesting and processing the many fur seals.

In these early years on the islands, Russian hunters so quickly decimated the fur seal population that the Russian-American Company, which held the charter for settling there, suspended hunting from 1805 to 1810. The annual limit for taking fur seals was then set at 8,000 to 10,000 pelts, allowing the population to rebound significantly.

The United States Arrives at the Islands

Fast forward to 1867, when the United States purchased Alaska, including the Pribilof Islands, from Russia for $7.2 million.

Some people considered the lucrative Pribilof Islands fur seal industry to have played a role in this purchase. In fact, this industry more than repaid the U.S. government for Alaska’s purchase price, hauling in $9,473,996 between 1870 and 1909.

The late 19th and early 20th centuries saw various U.S. military branches establish stations on the Pribilof Islands, as well as several (at times unsuccessful) attempts to control the reckless slaughter of fur seals. From 1867 until 1983, the U.S. government managed the fur seal industry on the Pribilof Islands.

In 1984, the Unangan finally were granted control of these islands, but the government had left behind a toxic legacy from commercial fur sealing and former defense sites: hazardous waste sites, dumps, contaminants, and debris.

Making Amends with the Land

This is where NOAA comes into the picture. In 1996, the Pribilof Islands Environmental Restoration Act called on NOAA to restore the environmental degradation on the Pribilof Islands. In particular, a general lack of historical accountability on the islands had led to numerous diesel fuel spills and leaks and improperly stored and disposed waste oils and antifreeze. By 1997 NOAA had removed thousands of tons of old cars, trucks, tractors, barrels, storage tanks, batteries, scrap metal, and tires from St. Paul and St. George Islands. Beginning in 2002, NOAA’s efforts transitioned to cleaning up soil contamination and assessing potential pollution in groundwater.

However, the Department of Defense has also been responsible for environmental cleanup at the Pribilof Islands. The U.S. Army occupied the islands during World War II and left behind debris and thousands of 55-gallon drums, which were empty by 1985 but had previously contained petroleum, oils, and lubricants, which could have leaked into the soil.

By 2008, NOAA’s Office of Response and Restoration had fulfilled its responsibilities for cleaning up the contamination on the Pribilof Islands, closing a dark chapter for this remote and diverse area of the world and hopefully continuing the healing process for the Unangan and fur seals who still call these islands their home.

Learn More about the Pribilof Islands

Man posing with schoolchildren.

Dr. G. Dallas Hanna with a class of Aleut schoolchildren on St. George Island, Alaska, circa 1914. (National Archives)

You can dig even deeper into the wealth of historical information about the Pribilof Islands at pribilof.noaa.gov.

There you can find histories, photos, videos, and documents detailing the islands’ various occupations, the fur seal industry, the relocation of the Unangan during World War II, the environmental contamination and restoration, and more.

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