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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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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To Save Corals in an Oahu Bay, First Vacuum up Invasive Algae, Then Apply Sea Urchins

Diver placing algae into Super Sucker vacuum hose.

With the help of a gentle vacuum hose attached to a barge — a device known as the “Super Sucker” — divers can now remove invasive algae from coral reefs in Kaneohe Bay in much less time. (Credit: State of Hawaii Division of Aquatic Resources)

Progress used to be painfully slow. On average, it would take a diver two strenuous hours to remove one square meter (roughly 10.5 square feet) of the exotic red algae carpeting coral reefs in Kaneohe Bay, Hawaii. In addition to ripping away thick mats of algae, divers also had to pluck off any remaining algae stuck to the reef and use a hand net to capture bits floating in the surrounding water. Even then, these invasive algae were quick to regrow from the tiniest remnants left behind.

Today, however, divers can clear the same area in roughly half the time, or even less, depending on how densely the algae are growing. How? With the help of a device called the “Super Sucker.”

This underwater vacuum is not much more than a barge equipped with a 40 horsepower pump and long hose that gets lowered into the water. Divers still pull off chunks of algae from the reef, but they then stuff it into the device’s hose. The steady, gentle suction of the Super Sucker pulls the algae—including any tiny drifting remnants—through the hose up to a mesh table on the barge. There, seawater drains out and any critters accidentally caught by the algae-vacuuming can be returned to the ocean. People on the barge can then pack the algae into mesh bags to be taken back to shore. (Watch a video of the Super Sucker at work.)

Super sucker barge with green collection hose in a tropical bay.

The Super Sucker barge at left in Kaneohe Bay. The green collection hose used to vacuum up invasive algae from the reefs below is visible on the water surface. (Credit: State of Hawaii Division of Aquatic Resources)

The success of the Super Sucker stands to be augmented with help from small, spiny sea creatures—sea urchins—as well as a new, dedicated infusion of funding from NOAA which will expand the device’s reach in Oahu’s Kaneohe Bay. But the question remains: How did exotic algae come to cause so much trouble for corals in the first place?

A Welcome Introduction, an Unintended Stay

The problematic marine algae, or seaweed, in Oahu’s Kaneohe Bay actually is a complex of two types of algae originally from Southeast Asia: Kappaphycus and Eucheuma. Both algae were brought to this area on the eastern side of Oahu in the 1970s in an attempt to cultivate them as a source of carrageenan, a thickening agent used in processed foods. While the agricultural endeavor never took off in Oahu, these algae did. Unfortunately, this was somewhat of a surprise. Two years after the algae’s introduction, several studies found a low likelihood of their escaping from experimental pens and threatening coral habitat in the bay.

In the decades since, Kappaphycus and Eucheuma have proven that prediction very wrong, as these algae are now comfortably established in Kaneohe Bay. Because these algae spread aggressively once they arrived in this new environment, they have earned the label “invasive.” The algae have been overgrowing the coral reefs, smothering and killing corals by blocking the sunlight these organisms need to survive. These days, some areas of Kaneohe Bay are no longer dominated by corals but instead by invasive algae.

Tumbleweed-like clumps of invasive algae on a coral reef.

Meet the complex of invasive algae plaguing coral reefs in Oahu’s Kaneohe Bay: Kappaphycus and Eucheuma. These thick, warty, plastic-like, and irregularly branching algae grow in tumbleweed-like clumps, often smothering coral beneath them. (Credit: State of Hawaii Division of Aquatic Resources)

Delivering a Double-Whammy to Invasive Algae

Around 2005, NOAA helped fund the development of the Super Sucker as part of a joint project between the State of Hawaii and the Nature Conservancy. The project was aimed at containing these invasive algae in Kaneohe Bay, a partnership that continues to the present day.

Today, NOAA is becoming involved once more by expanding this project and bringing the Super Sucker into new parts of Kaneohe Bay. NOAA will accomplish this by using part of the nearly $6 million available for restoration after the 2005 grounding of the ship M/V Cape Flattery. When the ship became lodged on coral reefs south of Oahu, efforts to refloat the vessel and avoid an oil spill caused extensive harm to coral habitat across approximately 20 acres, an area now recovering well on its own.

Sea urchins grazing on seaweed on a coral reef.

The native sea urchins eat away at any invasive algae left on the coral, keeping the algae’s growth in check. The State of Hawaii Division of Aquatic Resources is raising these urchins in captivity and releasing them into Kaneohe Bay. (Credit: State of Hawaii Division of Aquatic Resources)

This restoration project will not just involve the Super Sucker, however. Another key component in controlling invasive algae in Kaneohe Bay is reintroducing a native predator. While most plant-eating fish there prefer to graze on other, tastier algae, native sea urchins have shown they are happy to munch away at the tiniest scraps of Kappaphycus and Eucheuma found on reefs. But the number of sea urchins in Kaneohe Bay is unusually low.

Currently, the State of Hawaii Division of Aquatic Resources is raising native sea urchins and experimentally releasing them back into the bay. NOAA’s restoration project for the Cape Flattery coral grounding would greatly expand the combined use of the Super Sucker and reintroduced sea urchins to control the invasive algae.

Together, mechanically removing the algae with the Super Sucker and reintroducing sea urchins in the same area should be effective at curbing the regrowth and spread of invasive algae in the northern part of Kaneohe Bay. Making sure invasive algae do not spread outside the bay is an important part of this coral restoration project. This northern portion, near a major entrance to the bay, is a critical area for containing the algae and making sure it doesn’t escape from the bay to other near shore reefs.

Saving Corals and Creating Fertilizer

Top, coral reef with invasive algae. Bottom, same reef after algae was removed.

Top, coral reef before Super Sucker operations, and bottom, the same reef after the Super Sucker has cleared away the invasive algae. (Credit: State of Hawaii Division of Aquatic Resources)

Ultimately, the goal is to move toward natural controls (i.e., the sea urchins) taking over the containment of Kappaphycus and Eucheuma algae in Kaneohe Bay.

The benefits of removing the algae from the area’s coral reefs are two-fold. First, clearing away the carpets of algae saves the corals that are being smothered beneath them. Second, opening up other areas of the seafloor previously covered by algae creates space for young corals to settle and establish themselves, growing new reef habitat.

Another benefit of clearing the invasive algae in this project is that it provides a source of free fertilizer for local farmers. Not only does it offer a sustainable source of nutrients on agricultural fields but the algae breaks down more slowly and is therefore less susceptible than commercial fertilizer to leaching into nearby waterways.

Even so, a 2004 study confirmed that these algae do not survive in waters with low salt levels, meaning that any algae that do run off from farms into nearby streams will not eventually re-infect the marine environment. Another win.

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A Final Farewell to Oil Tankers with Single Hulls

January 1, 2015 marks a major milestone in preventing oil spills. That date is the deadline which the landmark Oil Pollution Act of 1990 (OPA-90) specifies for phasing out single-hull tankers in U.S. waters. That act, passed after the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska, required that all new tankers and tank-barges be built with double hulls.

Recently constructed single-hull tankers were allowed to operate, but 25 years after the Exxon Valdez, those vessels are now at the end of their operational life and will no longer be able to carry oil as cargo. The requirement was phased in gradually because of the difficultly of converting existing single-hull tankers to double hulls, and retiring the single-hull tankers more rapidly would have been a major disruption to world shipping.

Counting Down to a New Era

There won’t be a dramatic change-over on New Year’s Eve; most of the tankers calling on U.S. ports have had double hulls years before this deadline. However, one ship which was not switched over to a double hull soon enough was the tanker Athos I. This ship, carrying 13.6 million gallons of heavy crude oil, struck a submerged anchor in the Delaware River and caused a relatively large, complicated oil spill near Philadelphia, Pennsylvania, 10 year ago.

In 1992, two years after the Oil Pollution Act, the International Convention for the Prevention of Pollution from Ships (the MARPOL Convention) was amended to require all newly built tankers have double hulls. MARPOL has been ratified by 150 countries, representing over 99 percent of merchant tonnage shipped worldwide.

Stay out of Trouble by Going Double

So, what is the big issue around single vs. double-hull ships? Historically, tankers carrying oil were built with a single hull, or single shell.

While we measure oil in barrels, it is not actually shipped that way. Instead, oil is pumped into huge tanks that are part of the structure of tankers and barges. For vessels with a single hull, one plate of steel is all that separates the oil on board from the ocean. If the hull were punctured from a collision or grounding, an oil spill is pretty much guaranteed to follow. On the other hand, a ship with a double hull has two plates of steel with empty space in between them. The second hull creates a buffer zone between the ocean and the cargo of oil.

Naval architects have debated the merits of various hull designs in reducing oil spills, and using a double hull, essentially a hull within a hull, was selected as the preferred vessel design.

Close up of gash in hull on Cosco Busan cargo ship.

The cargo ship Cosco Busan lost 53,000 gallons of fuel oil when the single-hull ship hit the San Francisco-Oakland Bay Bridge in 2007. (U.S. Coast Guard)

However, the double hull requirements only apply to tankers and tank barges. Container ships, freighters, cruise ships, and other types of vessels are still built with single hulls. While these ships carry a lot less oil than a tanker, a large non-tank vessel can still carry a lot of fuel oil, and some have caused some pretty big spills, including the 2007 oil spill caused by the cargo ship Cosco Busan in San Francisco Bay.

Of course, double hulls don’t prevent all oil spills from tankers either, but the design has been credited with reducing the amount spilled, especially in the cases of low-speed groundings and collisions.

And some pretty spectacular collisions have resulted in double-hull tankers not spilling a drop.

Twenty years after the Exxon Valdez oil spill, the Norwegian tanker SKS Satilla collided with a submerged oil rig in the Gulf of Mexico. The collision tore a huge hole in the side of the oil tanker, but, thankfully, none of the 41 million gallons of crude oil it had on board was spilled.


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. [Update: Read how NOAA uses coral nurseries to restore damaged reefs.]

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You Say Collision, I Say Allision; Let’s Sort the Whole Thing Out

Despite improved navigation aids, including charts and Global Positioning Systems (GPS), ships still have accidents in our nation’s waterways, and I regularly review notification reports of these accidents from the National Response Center. Sometimes I need to consult the old nautical dictionary I inherited from my grandfather (a lawyer and U.S. Navy captain) to figure out what they mean.

Nautical terms and marine salvage books.

Keeping it all straight. (NOAA)

The U.S. Coast Guard investigates ship accidents, but they use the terms “marine casualty or accident” interchangeably [PDF]. Mariners are required to report any occurrence involving a vessel that results in:

  • Grounding
  • Stranding
  • Foundering
  • Flooding
  • Collision
  • Allision
  • Explosion
  • Fire
  • Reduction or loss of a vessel’s electrical power, propulsion, or steering capabilities
  • Failures or occurrences, regardless of cause, which impair any aspect of a vessel’s operation, components, or cargo
  • Any other circumstance that might affect or impair a vessel’s seaworthiness, efficiency, or fitness for service or route
  • Any incident involving significant harm to the environment

Some of those terms are pretty straightforward, but what is the difference between grounding and stranding? Or foundering and flooding? And my favorite, collision and allision?

Here is my basic understanding of these terms, but I am sure that some of these could fill an admiralty law textbook.

Groundings and strandings are probably the most common types of marine casualties. A grounding is when a ship strikes the seabed, while a stranding is when the ship then remains there for some length of time. Both can damage a vessel and result in oil spills depending on the ocean bottom type (rocky, sandy, muddy?), sea conditions, and severity of the event (is the ship a little scraped or did it break open?).

Flooding means taking on excessive water in one or more of the spaces on a ship (e.g., the engine room), while foundering is basically taking on water to the point where the vessel becomes unstable and begins to sink or capsize. Note that “foundering” is different than “floundering,” which is to struggle or move aimlessly.

And collision and allision … These terms are sometimes used interchangeably, but technically, a collision is when two vessels strike each other, while an allision occurs when a vessel strikes a stationary object, such as a bridge or dock.

Close up of large damaged ship with Coast Guard boat.

A U.S. Coast Guard boat approaches the gash in the side of the M/V Cosco Busan after it allided (rather than collided) with San Francisco’s Bay Bridge on November 7, 2007, releasing 53,000 gallons of bunker oil into San Francisco Bay. (U.S. Coast Guard)

No matter the proper terminology, all of these incidents can result in spills, keeping us pollution responders on our toes because of the potential impacts to coasts, marine life, and habitats such as coral reefs and seagrass beds. But understanding these various nautical terms helps us understand the circumstances we’re dealing with in an emergency and better adapt our science-based recommendations as a result. And as my grandfather used to say, a collision at sea can ruin your entire day …


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