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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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.

Read more: Deepwater Horizon Oil Spill Tied to Further Impacts in Shallower Water Corals, New Study Reports


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With Lobster Poacher Caught, NOAA Fishes out Illegal Traps from Florida Keys National Marine Sanctuary

This is a post by Katie Wagner of the Office of Response and Restoration’s Assessment and Restoration Division.

On June 26, 2014, metal sheets, cinder blocks, and pieces of lumber began rising to the ocean’s surface in the Florida Keys National Marine Sanctuary. This unusual activity marked the beginning of a project to remove materials used as illegal lobster fishing devices called “casitas” from sanctuary waters. Over the course of two months, the NOAA-led restoration team plans to visit 297 locations to recover and destroy an estimated 300 casitas.

NOAA’s Restoration Center is leading the project with the help of two contractors, Tetra Tech and Adventure Environmental, Inc. The removal effort is part of a criminal case against a commercial diver who for years used casitas to poach spiny lobsters from sanctuary waters. An organized industry, the illegal use of casitas to catch lobsters in the Florida Keys not only impacts the commercial lobster fishery but also injures seafloor habitat and marine life.

Casitas—Spanish for “little houses”—do not resemble traditional spiny lobster traps made of wooden slats and frames. “Casitas look like six-inch-high coffee tables and can be made of various materials,” explains NOAA marine habitat restoration specialist Sean Meehan, who is overseeing the removal effort.

The legs of the casitas can be made of treated lumber, parking blocks, or cinder blocks. Their roofs often are made of corrugated tin, plastic, quarter-inch steel, cement, dumpster walls, or other panel-like structures.

Poachers place casitas on the seafloor to attract spiny lobsters to a known location, where divers can return to quite the illegal catch.

A spiny lobster in a casita on the seafloor.

A spiny lobster in a casita. (NOAA)

“Casitas speak to the ecology and behavior of these lobsters,” says Meehan. “Lobsters feed at night and look for places to hide during the day. They are gregarious and like to assemble in groups under these structures.” When the lobsters are grouped under these casitas, divers can poach as many as 1,500 in one day, exceeding the daily catch limit of 250.

In addition to providing an unfair advantage to the few criminal divers using this method, the illegal use of casitas can harm the seafloor environment. A Natural Resource Damage Assessment, led by NOAA’s Restoration Center in 2008, concluded that the casitas injured seagrass and hard bottom areas, where marine life such as corals and sponges made their home. The structures can smother corals, sea fans, sponges, and seagrass, as well as the habitat that supports spiny lobster, fish, and other bottom-dwelling creatures.

Casitas are also considered marine debris and potentially can harm other habitats and organisms. When left on the ocean bottom, casitas can cause damage to a wider area when strong currents and storms move them across the seafloor, scraping across seagrass and smothering marine life.

“We know these casitas, as they are currently being built, move during storm events and also can be moved by divers to new areas,” says Meehan. However, simply removing the casitas will allow the seafloor to recover and support the many marine species in the sanctuary.

There are an estimated 1,500 casitas in Florida Keys National Marine Sanctuary waters, only a portion of which will be removed in the current effort. In this case, a judge ordered the convicted diver to sell two of his residences to cover the cost of removing hundreds of casitas from the sanctuary.

To identify the locations of the casitas, NOAA’s Hydrographic Systems and Technology Program partnered with the Restoration Center and the Florida Keys National Marine Sanctuary. In a coordinated effort, the NOAA team used Autonomous Underwater Vehicles (underwater robots) to conduct side scan sonar surveys, creating a picture of the sanctuary’s seafloor. The team also had help finding casitas from a GPS device confiscated from the convicted fisherman who placed them in the sanctuary.

After the casitas have been located, divers remove them by fastening each part of a casita’s structure to a rope and pulley mechanism or an inflatable lift bag used to float the materials to the surface. Surface crews then haul them out of the water and transport them to shore where they can be recycled or disposed.

For more information about the program behind this restoration effort, visit NOAA’s Damage Assessment, Remediation, and Restoration Program.

Katie Wagner.Katie Wagner is a communications specialist in the Assessment and Restoration Division of NOAA’s Office of Response and Restoration. Her work raises the visibility of NOAA’s effort to protect and restore coastal and marine resources following oil spills, releases of hazardous substances, and vessel groundings.


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Investigating Environmental Impacts: Oil on the Kalamazoo River

Posted sign closing river activity due to oil spill response.

The Kalamazoo River has been closed to the public since the spill in 2010. We’re examining how this has affected public recreation and tribal cultural uses. (Terry Heatlie, NOAA)

In late summer of 2010, while the nation was fixated on the massive oil spill in the Gulf of Mexico, an underground pipeline in Michigan also began gushing oil. My job has been to help investigate the environmental damage that spill caused when the oil flowed into the Kalamazoo River.

The Situation
More than 800,000 gallons of crude oil** poured out of the leaking pipeline before it was eventually shut off. It oozed through the soft, wet ground just outside of Marshall, Mich., before washing into the Kalamazoo River, one of the largest rivers in southern Michigan.

I was at a meeting in Milwaukee with my suitcase full of sandals and skirts — not exactly dressed for an oil spill — when I got called to the scene. I drove nearly nonstop to Marshall, with only a quick detour in Indiana to buy steel-toed boots and work pants.

The Challenges
When I arrived, the other scientists and I made plans to collect data on the oil’s damage. Heavy rains had caused the river to flood over its banks, and as the oil flowed approximately forty miles* down the Kalamazoo, it was also carried up onto the banks and into trees. As the flood waters receded, oil was left on overhanging branches and in floodplains.

As the flood water receded, oil was left behind on river vegetation and overhanging tree branches, as well as in yards and forested floodplains. Yellow containment boom is in the foreground. (Gene Suuppi, State of Michigan)

The river’s floodplains, full of forests and wetlands, are also home to sensitive seasonal ponds, which provide valuable habitat for fish and macroinvertebrates (aquatic “bugs” at the base of the food chain). Therefore, we needed to find out: how far did the oil make it into the floodplain, what did it contact while there, and how much oil was left?

The smell of oil was sickeningly strong at first. Residents evacuated the houses nearest to the leak, and workers within half a mile of the pipeline break had to wear respirators to protect them from inhaling fumes. Even a dozen miles downstream, I could smell the oil and feel the fumes irritating my eyes. These fumes were the light components of the oil evaporating into the air. The heavy components of the oil were left behind on the banks or gradually sank to the bottom of the river.

The sunken oil has proven difficult to clean up. This winter, spill responders have been working to quantify how much sunken oil is left and to develop and test techniques for cleaning it up.

The Science
Along with my team from NOAA’s Office of Response and Restoration, the U. S. Fish and Wildlife Service, the State of Michigan, and the Huron Band and Gun Lake Tribe of the Potawatomi joined together as trustees to assess damages that the spill caused to natural resources.

We’ve conducted a variety of studies to collect information on the impacts of the spill and repeated some of the studies to see how the environment is recovering. Now we’re gathering all this data for the official damage assessment. We’ve examined samples of fish, mussels, water, and sediments for evidence of oil-related chemicals. We’ve collected observations of oiled vegetation and records of the number and condition of animals brought to the wildlife rehab center.

Talmadge Creek cleanup crews on Aug 6, 2010.

Cleanup crews place absorbent pads to sop up oil at Talmadge Creek, near the source of the spill, on Aug 6, 2010. We also take into account the effect cleanup has on the environment. (Chuck Getter)

Unfortunately, cleanup-related activities have an environmental impact too. For example, extra boat traffic on the river during cleanup led to some riverbank erosion and crushed freshwater mussels. Our studies include these factors too. We’ll also look into the effect the spill had on public recreation (the river has been closed to the public since the spill) and on tribal cultural uses.

What Next?
We and the other trustees will seek out restoration projects that address the impacts caused by the spill, being careful to balance the projects with the results of our studies. We’ll take project ideas from the public and from watershed organizations to make sure that we choose projects that fit in well with other restoration work being done across the broader Kalamazoo River watershed.

Enbridge Energy, as the owner of the pipeline, will have the option to implement the projects themselves with oversight from us trustees, or could pay for the cost of these projects as part of a larger legal settlement.

Stay tuned and we’ll keep you updated as this story unfolds.

*Correction: This originally stated that the oil flowed thirty miles down the Kalamazoo River.

**This was later discovered to be an oil sands (or tar sands) product.