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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How NOAA Uses Coral Nurseries to Restore Damaged Reefs

Staghorn coral fragments hanging on an underwater tree structure of PVC pipes.

NOAA uses coral nurseries to help corals recover after traumatic events, such as a ship grounding. Hung on a tree structure, the staghorn coral shown here will have a better chance of surviving and being transplanted back onto a reef. (NOAA)

The cringe-inducing sound of a ship crushing its way onto a coral reef is often the beginning of the story. But, thanks to NOAA’s efforts, it is not usually the end. After most ship groundings on reefs, hundreds to thousands of small coral fragments may litter the ocean floor, where they would likely perish rolling around or buried under piles of rubble. However, by bringing these fragments into coral nurseries, we give them the opportunity to recover.

In the waters around Florida, Puerto Rico, and the U.S. Virgin Islands, NOAA works with a number of partners in various capacities to maintain 27 coral nurseries. These underwater safe havens serve a dual function. Not only do they provide a stable environment for injured corals to recuperate, but they also produce thousands of healthy young corals, ready to be transplanted into previously devastated areas.

Checking into the Nursery

When they enter coral nurseries, bits of coral typically measure about four inches long. They may come from the scene of a ship grounding or have been knocked loose from the seafloor after a powerful storm. Occasionally and with proper permission, they have been donated from healthy coral colonies to help stock nurseries. These donor corals typically heal within a few weeks. In fact, staghorn and elkhorn coral, threatened species which do well in nurseries, reproduce predominantly via small branches breaking off and reattaching somewhere new.

In the majority of nurseries, coral fragments are hung like clothes on a clothesline or ornaments on trees made of PVC pipes. Floating freely in the water, the corals receive better water circulation, avoid being attacked by predators such as fireworms or snails, and generally survive at a higher rate.

After we have established a coral nursery, divers may visit as little as a few times per year or as often as once per month if they need to keep algae from building up on the corals and infrastructure. “It helps if there is a good fish population in the area to clean the nurseries for you,” notes Sean Griffin, a coral reef restoration ecologist with NOAA.

Injured corals generally take at least a couple months to recover in the nurseries. After a year in the nursery, we can transplant the original staghorn or elkhorn colonies or cut multiple small fragments from them, which we then use either to expand the nursery or transplant them to degraded areas.


One of the fastest growing species, staghorn coral can grow up to eight inches in a year while elkhorn can grow four inches. We are still investigating the best ways to cultivate some of the slower growing species, such as boulder star coral and lobed star coral.

Growing up to Their Potential

In 2014, we placed hundreds of coral fragments from four new groundings into nurseries in Puerto Rico and the U.S. Virgin Islands. This represents only a fraction of this restoration technique’s potential.

After the tanker Margara ran aground on coral reefs in Puerto Rico in 2006, NOAA divers rescued 11,000 salvageable pieces of broken coral, which were reattached at the grounding site and established a nursery nearby using 100 fragments from the grounding. That nursery now has 2,000 corals in it. Each year, 1,600 of them are transplanted back onto the seafloor. The 400 remaining corals are broken into smaller fragments to restock the nursery. We continue to grow healthy corals in this nursery and then either transplant them back to the area affected by the grounded ship, help restore other degraded reefs, or use some of them to start the process over for another year.

Nurseries in Florida, Puerto Rico, and the U.S. Virgin Islands currently hold about 50,000 corals. Those same nurseries generate another 50,000 corals which we transplant onto restoration sites each year. Sometimes we are able to use these nurseries proactively to protect and preserve corals at risk. In the fall of 2014, a NOAA team worked with the University of Miami to rescue more than 200 threatened staghorn coral colonies being affected by excessive sediment in the waters off of Miami, Florida. The sedimentation was caused by a dredging project to expand the Port of Miami entrance channel.

We relocated these colonies to the coral nurseries off Key Biscayne run by our partners at the University of Miami. The corals were used to create over 1,000 four-inch-long fragments in the nursery. There, they will be allowed to recover until dredge operations finish at the Port of Miami and sedimentation issues are no longer a concern. The corals then can either be transplanted back onto the reef where they originated or used as brood stock in the nursery to propagate more corals for future restoration.


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When Ships Threaten Corals in the Caribbean, NOAA Dives to Their Rescue

Growing less than a quarter inch per year, the elaborate coral reefs off the south coast of Puerto Rico originally took thousands of years to form. And over the course of two days in late April 2006, portions of them were ground into dust.

The tanker Margara ran aground on these reefs near the entrance to Guayanilla Bay. Then, in the attempt to remove and refloat the ship, it made contact with the bottom several times and became grounded again. By the end, roughly two acres of coral were lost or injured. The seafloor was flattened and delicate corals crushed. Even today, a carpet of broken coral and rock remains in part of the area. This loose rubble becomes stirred up during storms, smothering young coral and preventing the reef’s full recovery.

NOAA and the Puerto Rico Department of Natural and Environmental Resources have been working on a restoration plan for this area, a draft of which they released for public comment in September 2014 [PDF]. In order to stabilize these rubble fields and return topographic complexity to the flattened seafloor, they proposed placing limestone and large boulders over the rubble and then transplanting corals to the area.

This is in addition to two years of emergency restoration actions, which included stabilizing some of the large rubble, reattaching around 10,500 corals, and monitoring the slow comeback and survival of young coral. In the future, even more restoration will be in the works to make up for the full suite of environmental impacts from this incident.

Caribbean Cruising for a Bruising

Unfortunately, the story of the Margara is not an unusual one. In 2014 alone, NOAA received reports of 37 vessel groundings in Puerto Rico and the U.S. Virgin Islands. About half of these cases threatened corals, prompting NOAA’s Restoration Center to send divers to investigate.

After a ship gets stuck on a coral reef, the first step for NOAA is assessing the situation underwater. If the vessel hasn’t been removed yet, NOAA often provides the salvage company with information such as known coral locations and water depths, which helps them determine how to remove the ship with minimal further damage to corals. Sometimes that means temporarily removing corals to protect them during salvage or figuring out areas to avoid hitting as the ship is extracted.

Once the ship is gone, NOAA divers estimate how many corals and which species were affected, as well as how deep the damage was to the structure of the reef itself. This gives them an idea of the scale of restoration needed. For example, if less than 100 corals were injured, restoration likely will take a few days. On the other hand, dealing with thousands of corals may take months.

NOAA already has done some form of restoration at two-thirds of the 18 vessel groundings with coral damage in the region this year. They have reattached 2,132 corals to date.

What does this look like? At first, it’s a lot of preparation. Divers collect the corals and fragments knocked loose by the ship; transport them to a safe, stable underwater location where they won’t be moved around; and dig out any corals buried in debris. When NOAA is ready to reattach corals, divers clear the transplant area (sometimes that means using a special undersea vacuum). On the ocean surface, people in a boat mix cement and send it down in five-gallon buckets to the divers below. Working with nails, rebar, and cement, the divers carefully reattach the corals to the seafloor, with the cement solidifying in a couple hours.

Protecting Coral, From the Law to the High Seas

Corals freshly cemented to the seafloor.

Corals freshly cemented to the seafloor. After a couple weeks, the cement becomes colonized by algae and other marine life so that it blends in with the reef. (NOAA)

Nearly a third of the total reported groundings in Puerto Rico and the U.S. Virgin Islands this year have involved corals listed as threatened under the Endangered Species Act. In previous years, only 10 percent of the groundings involved threatened corals. What changed this year was the Endangered Species Act listing of five additional coral species in the Caribbean.

Another form of protection for corals is installing buoys to mark the location of reefs in areas where ships keep grounding on them. Since these navigational aids were put in place at one vulnerable site in Culebra, Puerto Rico this summer, NOAA hasn’t been called in to an incident there yet.

But restoring coral reefs after a ship grounding almost wouldn’t be possible without coral nurseries. Here, NOAA is able to regrow and rehabilitate coral, a technique being used at the site of the T/V Margara grounding. Stay tuned because we’ll be going more in depth on coral nurseries, what they look like, and how they help us restore these amazingly diverse ocean habitats.


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How Ghost Fishing Is Haunting Our Ocean

No, ghost fishing has nothing to do with ghostbusters flicking fishing rods from a boat.

But what is ghost fishing? It’s a not-at-all-supernatural phenomenon that occurs when lost or discarded fishing gear remains in the ocean and continues doing what it was made to do: catch fish. These nets and traps haunt the many types of marine life unlucky enough to become snared in them. That includes species of turtles, fish, sharks, lobsters, crabs, seabirds, and marine mammals.

Fortunately, the NOAA Marine Debris Program isn’t scared off by a few fishing nets that haven’t moved on from the underwater world. For example, through the Fishing for Energy partnership, NOAA is funding projects to study and test ways to keep fishers from losing their gear in the first place and lower the impacts lost gear has on marine life and their homes.

You can learn more about these four recent projects which are taking place from the South Carolina coast to Washington’s Puget Sound. A project at the Virginia Institute of Marine Science at The College of William and Mary will pay commercial fishermen to test special biodegradable panels on crab pots. After a certain amount of time underwater, these panels will break down and begin allowing creatures to escape from the traps. If successful, this feature could help reduce the traps’ ghost fishing potential. The researchers also will be examining whether terrapin turtles, a declining species often accidentally drowned in crab pots, will bypass the traps based on the color of the entrance funnel.

Another, unrelated effort which NOAA and many others have been supporting for years is focused on fishing out the thousands of old salmon nets lost—sometimes decades ago—in Washington’s Puget Sound. These plastic mesh nets sometimes remain drifting in the water column, while other times settling on the seafloor, where they also degrade the bottom habitat.

According to Joan Drinkwin of the Northwest Straits Foundation, the organization leading the effort, “They become traps for fish, diving birds, and mammals. Small fish will dart in and out of the mesh and predators will go after those fish and become captured in the nets. And as those animals get captured in the nets, they become bait for more scavengers.”

You can watch a video about this ongoing project produced by NOAA-affiliate Oregon SeaGrant to learn more about both the problem and the solutions.

Scuba diver next to huge mass of fishing nets underwater.

This “super net” was first reported in September 2013 at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands. In 2014 scuba and free divers removed this mass of fishing gear that was more than 28 feet long, 7 feet wide, and had a dense curtain that extended 16 feet deep. (NOAA)

Thousands of miles away from the Pacific Northwest, ghost nets are also an issue for the otherwise vibrant coral reefs of the Northwestern Hawaiian Islands. Every year for nearly two decades, NOAA has been removing the lost fishing nets which pile up on the atolls and small islands. This year, divers cleared away 57 tons of old fishing nets and plastic debris. One particularly troubling “super net” found this year measured 28 feet by 7 feet and weighed 11.5 tons. It had crushed coral at Pearl and Hermes Atoll and was so massive that divers had to cut it into three sections to be towed individually back to the main NOAA ship. During this year’s mission, divers also managed to free three protected green sea turtles which were trapped in various nets.

But the origins of this huge and regular flow of old fishing nets to the Northwestern Hawaiian Islands remain a mystery. The islands lay hundreds of miles from any city but also within an area where oceanic and atmospheric forces converge to accumulate marine debris from all over the Pacific Ocean.

“You’ll go out there to this remote place and pull tons of this stuff off a reef,” comments Jim Potemra, an oceanographer at the University of Hawaii at Mānoa, “that’s like going to Antarctica and finding two tons of soda cans.”

You can learn more about the NOAA Marine Debris Program’s efforts related to ghost fishing and why certain types of marine life may be more likely to get tangled up in discarded nets and other ocean trash.


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Untangling Both a Whale and Why Marine Life Get Mixed up With Our Trash

Tail-view of humpback whale tangled in rope and nets underwater.

A humpback whale entangled in fishing gear swims near the ocean’s surface in 2005. (NOAA/Hawaiian Islands Humpback Whale National Marine Sanctuary)

In the United States alone, scientific reports show at least 115 different species of marine life have gotten tangled up—literally—in the issue of marine debris. And when you look across the globe that number jumps to 200 species. Those animals affected range from marine mammals and sea turtles to sea birds, fish, and invertebrates.

Sadly, a humpback whale (Megaptera novaeangliae) swimming in the blue waters off of Maui, Hawaii, got first-hand experience with this issue in February 2014. Luckily, trained responders from the Hawaiian Islands Humpback Whale National Marine Sanctuary were able to remove the long tangle of fishing rope wrapped around the whale’s head, mouth, and right pectoral fin. According to NOAA’s National Marine Sanctuaries:

“A long pole with a specially designed hook knife was used by trained and permitted personnel to cut through the entanglement.

Hundreds of feet of small gauge line were collected after the successful disentanglement. The entanglement was considered life threatening and the whale is confirmed to be totally free of gear.”

Check out these short videos taken by the response team for a glimpse of what it’s like trying to free one of these massive marine mammals from this debris:

Net Results

While this whale was fortunate enough to have some help escaping, the issue of wildlife getting tangled in marine debris is neither new nor going away. Recently, the NOAA Marine Debris Program and National Centers for Coastal Ocean Science reviewed scientific reports of ocean life entangled by marine debris in the United States. You can read the full NOAA report [PDF].

They looked at more than 170 reports reaching all the way back to 1928. However, wildlife entanglements didn’t really emerge as a larger problem until after 1950 and into the 1970s when plastic and other synthetic materials became popular. Before that time, fishing gear and “disposable” trash tended to be made out of materials that broke down in the environment, for example, hemp rope or paper bags. Nowadays, when plastic packing straps and nylon fishing ropes get lost or discarded in the ocean, they stick around for a lot longer—long enough for marine life to find and get wrapped up in them.

One of the findings of the NOAA report was that seals and sea lions (part of a group known as pinnipeds) were the type of marine life most likely to become entangled in nets and other debris in the United States. Sea turtles were a close second.

But why these animals? Is there something that makes them especially vulnerable to entanglement?

Location, Location, Location

The two species with the highest reported numbers of entanglements were northern fur seals (Callorhinus ursinus) and Hawaiian monk seals (Monachus schauinslandi). Both of these seals may live in areas where marine debris tends to build up in higher concentrations, increasing their chances of encountering and getting tangled in it.

For example, Hawaiian monk seals live among the coral reefs of the Northwestern Hawaiian Islands, where some 50 tons of old fishing gear washes up each year. These islands are near the North Pacific Subtropical Convergence Zone, where oceanic and atmospheric forces bring together not only plenty of food for marine life but also lots of debris floating in the ocean. Humpback whales migrate across these waters twice a year, which might be how the humpback near Maui ended up in a tangled mess earlier this year.

Just Behave

Monk sleep sleeping on nets on beach.

An endangered Hawaiian monk seal snuggles up on a pile of nets and other fishing gear in the Northwestern Hawaiian Islands. Between the mid-1950s and mid-1990s, the population declined to one-third of its size due at least in part to entanglement in trawl nets and other debris that drift into the Northwestern Hawaiian Islands from other areas (e.g., Alaska, Russia, Japan) and accumulates along the beaches and in lagoon reefs of atolls. (NOAA)

While being in the wrong place at the wrong time can lead to many unhappily tangled marine animals, behavior also plays into the problem. Some species exhibit particular behaviors that unknowingly put them at greater risk when marine debris shows up.

Not only does the endangered Hawaiian monk seal live on shores prone to the buildup of abandoned nets and plastic trash, but the seals actually seem to enjoy a good nap or lounge on piles of old fishing gear, according to visiting scientists in the Northwestern Hawaiian Islands. The playful, curious nature of young seals and humpback whales also makes them more likely to become entangled in marine debris.

Sea turtles, young and old, are another group whose behaviors evolved to help them survive in a world without human pollution but which in today’s world sometimes place them in harm’s way. Young sea turtles like to hide from predators under floating objects, which too often end up being marine debris. And because sea turtles enjoy munching on the food swirling around ocean convergence zones, such as the one in the North Pacific, they also munch on and get mixed up with the marine debris that gathers there too—especially items with loops and openings to get caught on.

While these animals can’t do much about their behaviors, we humans can. You can:


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Follow Along as NOAA Clears the Waters of the Northwestern Hawaiian Islands

Two people pull nets from the ocean into a small boat.

Two members of the NOAA dive team remove derelict fishing gear from a reef at Midway Atoll during the 2013 marine debris removal cruise. (NOAA)

Turquoise waters, vibrant coral reefs, white sand beaches—this is often what we think of when we think about far-off islands in the Pacific Ocean. But even the furthest reaches of wilderness, such as the tropical reefs, islands, and atolls of the Papahānaumokuākea Marine National Monument, which are hundreds of miles from the main Hawaiian archipelago, can be polluted by human influence. In these shallow waters, roughly 52 tons of plastic fishing nets wash up on coral reefs and shorelines each year.

For nearly two decades, NOAA has been leading an annual mission to clean up these old nets that can smother corals and entangle marine life, including endangered Hawaiian monk seals. This year, the NOAA Marine Debris Program has two staff—Dianna Parker and Kyle Koyanagi—joining the NOAA Pacific Islands Fisheries Science Center scientists and divers on board the NOAA Ship Oscar Elton Sette to document this effort.

A man pulls a net out of the ocean into a small boat.

Chief scientist Mark Manuel hauls derelict nets over the side of a small boat at Maro Reef during the 2014 expedition. (NOAA)

You can follow their journey to remove nets from five areas in the marine monument:

You can keep track of all things related to this expedition on the NOAA Marine Debris Program website.


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How to Restore a Damaged Coral Reef: Undersea Vacuums, Power Washers, and Winter Storms

NOAA Fisheries Biologist Matt Parry contributed to this story and this restoration work.

After a ship runs aground on a coral reef, the ocean bottom becomes a messy place: thickly carpeted with a layer of pulverized coral several feet deep. This was the scene underwater off the Hawaiian island of Oahu in February of 2010. On February 5, the cargo ship M/T VogeTrader ran aground and was later removed from a coral reef in the brilliant blue waters of Kalaeloa/Barber’s Point Harbor.

NOAA and our partners suited up in dive gear and got to work restoring this damaged reef, beginning work in October 2013 and wrapping up in April 2014. While a few young corals have begun to repopulate this area in the time since the grounding, even fast-growing corals grow less than half an inch per year. The ones there now are mostly smaller than a golf ball and the seafloor was still covered in crushed and dislodged corals. These broken corals could be swept up and knocked around by strong currents or waves, potentially causing further injury to the recovering reef. This risk was why we pursued emergency restoration [PDF] activities for the reef.

What we didn’t expect was how a strong winter storm would actually help our restoration work in a way that perhaps has never before been done.

How Do You Start Fixing a Damaged Reef?

First, we had to get the lay of the (underwater) land, using acoustic technology to map exactly where the coral rubble was located and determine the size of the affected area. Next, our team of trained scuba divers gathered any live corals and coral fragments and transported them a short distance away from where they would be removing the rubble.

Then, we were ready to clean up the mess from the grounding and response activity and create a place on the seafloor where corals could thrive. Divers set up an undersea vacuum on the bottom of the ocean, which looks like a giant hose reaching 35 feet down from a boat to the seafloor. It gently lifted rubble up through the hose—gently, because we wanted to avoid ripping everything off of the seafloor. Eventually, our team would remove nearly 800 tons (more than 700 metric tons) of debris from the area hit by the ship.

Unexpected Gifts from a Powerful Storm

In the middle of this work, the area experienced a powerful winter storm, yielding 10-year high winter swells that reduced visibility underwater and temporarily halted the restoration work. When the divers returned after the storm subsided, they were greeted by a disappointing discovery: the cache of small coral remnants they had stockpiled to reattach to the sea bottom was gone. The swells had scoured the seafloor and scattered what they had gathered.

But looking around, the divers realized that the energetic storm had broken off and dislodged a number of large corals nearby. Corals that were bigger than those they lost and which otherwise would have died as a result of the storm. With permission from the State of Hawaii, they picked up some of these large, naturally detached corals, which were in good condition, and used them as donor corals to finish the restoration project.

Finding suitable donor corals is one of the most difficult aspects of coral restoration. This may have been the first time people have been able to take advantage of a naturally destructive event to restore corals damaged by a ship grounding.

A Reef Restored

Once our team transported the donor corals to the restoration site a few hundred yards away, they scraped the seafloor, at first by hand and then with a power washer, to prepare it for reattaching the corals. Using a cement mixer on a 70-foot-long boat, they mixed enough cement to secure 643 corals to the seafloor.

While originally planning to reattach 1,200 coral colonies, the storm-blown corals were so large (and therefore so much more valuable to the recovering habitat) that the divers ran out of space to reattach the corals. In the end, they didn’t replace these colonies in the exact same area that they removed the coral rubble. When the ship hit the reef, it displaced about three feet of reef, exposing a fragmented, crumbly surface below. They left this area open for young corals to repopulate but traveled a little higher up on the reef shelf to reattach the larger corals on a more secure surface, one only lightly scraped by the ship.

The results so far are encouraging. Very few corals were lost during the moving and cementing process, and the diversity of coral species in the reattachment area closely reflects what is seen in unaffected reefs nearby. These include the common coral species of the genus Montipora (rice coral), Porites lobata (lobe coral), and Pocillopora meandrina (cauliflower coral). As soon as the divers finished cleaning and cementing the corals to the ocean floor, reef fish started moving in, apparently pleased with the state of their new home.

But our work isn’t done yet. We’ll be keeping an eye on these corals as they recover, with plans to return for monitoring dives in six months and one year. In addition, we’ll be working with our partners to develop even more projects to help restore these beautiful and important parts of Hawaii’s undersea environment.


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How Do Oil Spills Affect Coral Reefs?

Coral habitat in the Hawaiian Islands.

Coral habitat in the Hawaiian Islands. (NOAA)

A warming, more acidic ocean. Grounded ships and heavy fishing nets. Coral reefs face a lot of threats from humans. For these tiny animals that build their own limestone homes underwater, oil spills may add insult to injury.

But how does spilled oil reach coral reefs? And what are the effects?

How an oil spill affects corals depends on the species and maturity of the coral (e.g., early stages of life are very sensitive to oil) as well as the means and level of exposure to oil. Exposing corals to small amounts of oil for an extended period can be just as harmful as large amounts of oil for a brief time.

Coral reefs can come in contact with oil in three major ways:

  1. Oil floating on the water’s surface can be deposited directly on corals in an intertidal zone when the water level drops at low tide.
  2. Rough seas can mix lighter oil products into the water column (like shaking up a bottle of salad dressing), where they can drift down to coral reefs.
  3. As heavy oil weathers or gets mixed with sand or sediment, it can become dense enough to sink below the ocean surface and smother corals below.

 

Oil slicks moving onto coral reefs at Galeta at low tide after the Bahia las Minas refinery spill, Panama, in April 1986.

Oil slicks moving onto coral reefs at Galeta at low tide after the Bahia las Minas refinery spill, Panama, in April 1986. (NOAA)

Once oil comes into contact with corals, it can kill them or impede their reproduction, growth, behavior, and development. The entire reef ecosystem can suffer from an oil spill, affecting the many species of fish, crabs, and other marine invertebrates that live in and around coral reefs.

As oil spill responders, NOAA’s Office of Response and Restoration has to take these and many other factors into account during an oil spill near coral reefs. For example, if the spill resulted from a ship running aground on a reef, we need to consider the environmental impacts of the options for removing the ship. Or, if an oil spill occurred offshore but near coral reefs, we would advise the U.S. Coast Guard and other pollution responders to avoid using chemical dispersants to break up the oil spill because corals can be harmed by dispersed oil.

We also provide reports and information for responders and natural resource managers dealing with oil spills and coral reefs:

You can learn more about coral reefs, such as the basic biology of corals, how damaged coral reefs can recover from an oil spill or be restored after a ship grounding, and what we’ve learned about oil spills in tropical reefs.

For lessons a little closer to home, be sure to find out five more things you should know about coral reefs and listen to this podcast about threats to coral health from NOAA’s National Ocean Service.

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