Selected tag(s): Deepwater Corals

Deepwater Corals Are Out of Sight, But They Shouldn’t Be Out of Mind

Credit: Steve W. Ross (UNCW), unpubl. data.

Among the unseen and uncounted victims of the BP oil disaster in the Gulf of Mexico are the inhabitants of the ancient deepwater coral reefs that lie under the still-growing plume of oil.  Newly discovered, and still largely unexplored, these “rainforests of the deep” may become polluted and degraded before we even know exactly where they occur.

Deepwater wonders

Deepwater corals were first discovered in U.S. waters in the 19th century, during the early voyages of discovery, but only in the modern age of deepsea submarines and remotely operated vehicles did exploration truly begin.

Credit: Steve W. Ross (UNCW), unpubl. data.

As exploration has unfolded, scientists have been amazed at the extent and character of these underwater wonderlands, with new species being discovered with nearly every dive, including unknown forms with the potential to contain novel chemicals with pharmaceutical applications.  A cancer cure may lie in the darkness of the deep sea. 

Additionally, the branches of millennia-old corals have recorded in their layers an unequalled history of the recent life of the planet, including deepsea conditions that will allow ancient climates to be modeled.


Gulf of Mexico coral reefs

Credit: Geoplatform.gov

Credit: USGS

 Click images for larger view

The best-known deepwater reefs in the Gulf are located in the Viosca Knolls region, on the northern edge of the DeSoto Canyon, only twenty miles from the blown-out BP well, and on the edge of the Mississippi Canyon west of the blowout site.  In addition, there are known deepwater reefs off the West Florida Shelf and elsewhere in the Gulf.  Exciting research is currently underway in the Gulf, including the deployment of “lunar lander” data recorders for year-long stays on the bottom near the reefs, which could provide badly needed baseline information for pre-blowout conditions.

See a thorough analysis of coral reefs in the Gulf, Southeast and elsewhere here.

Toxins raining down on corals

The deepwater origin of the BP oil disaster, the use of dispersants at the wellhead, and the resulting development of sub-surface plumes of oil-based pollution floating and drifting with sub-surface currents, mean that Gulf deepwater corals are at serious risk of direct degradation from the broken well, including a wide array of materials that would likely prove toxic to them. Normally, at least some of the toxic substances from an oil spill would evaporate as oil sits on the ocean surface, but in this situation, many of the toxins remain dissolved, emulsified or otherwise entrained in near-bottom waters and middle depths, drifting with the currents and potentially exposing deepwater reefs.   Coral’s naturally slow growth rates and uncertain reproduction means that any damage would be difficult if not impossible to remediate or offset.

To make matters worse, oil that does make it to the ocean surface doesn’t stay there.  While some of the toxic material on the surface is burned or evaporated, much is again treated with dispersant chemicals, forming smaller droplets that easily stick to debris raining into the abyss.  In addition, a significant fraction of weathered oil also ultimately sinks back to the depths of the ocean. Although estimates vary widely, the best guess is that 25-30% or so of the oil from the 1979 Ixtoc 1 blowout in Campeche Bay in the southwestern Gulf sank to the bottom.

Credit: LUMCON

Another real threat comes from the decomposition of oil-based organic matter under water.  “Dead zones” are well-known in the shallower waters of the northern Gulf, driven mostly by nutrients and organic matter from the outflows from the Mississippi River.  In this case, underwater “dead zones” at a variety of depths are likely, and could add an additional punch to fragile ancient corals.

Protecting deepwater treasures

Credit: SAFMC

Ironically, as Gulf coral reefs face an uncertain future, thousands of square miles of reefs are being protected in a new program nearby in the Southeast Atlantic. I had the great privilege of chairing the panel responsible for this magnificent advance. 

Over the past decade, a unique collaboration of academic researchers, managers and fishermen have worked together to craft a landmark protection program for 23,000 square miles of deepwater reefs stretching from North Carolina to Florida.  The National Oceanic and Atmospheric Administration approved these protections just this month, which will protect the coral reefs against fishing and many non-fishing threats.  While this designation by itself does not guarantee that oil and gas drilling could not occur there, it means that risks to those corals would have to be taken into account during lease sales and other project planning and design.

Two of the many researchers instrumental in securing these coral protections—Dr. Steve Ross from UNC Wilmington and Dr. John Reed from Harbor Branch—have each published their corals research online.

Corals in the crosshairs

The bottom line, sadly, is that ancient Gulf of Mexico coral reefs lie in the crosshairs of oil pollution from the BP oil disaster and it will be some time before scientists are able to begin damage assessments.  Research cruises scheduled for September may begin that process.

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Unseen Victims of the BP Oil Disaster


Floating mats of seaweed, known as sargassum, are home to a wide variety of ocean life. Credit: Steve W. Ross (UNCW), unpubl. data.

The daily count of sea creatures dying from coating with oil on the surface of the sea, or on the beaches, continues to rise.  We see sea turtles, sea and shore birds, and marine mammals, familiar creatures to us all.

As sad as these deaths are, the death toll is massively greater for animals not quite as visible, because they are small, living among marsh grasses, or under the surface of the sea, out-of-sight and thus out-of-mind.  The full litany of the dead is deeply disturbing.

Surface currents carry valuable life

The surface waters of a healthy Gulf swim with life, much of it too small to see.  Larvae of shrimp, crab, and other shellfish, and many familiar seafood fishes, spawned at sea, drift toward nurseries in coastal marshes and other shallow waters. Floating mats of seaweed, called sargassum, provide key habitats for babies of many species, now hopelessly contaminated. The interior and underside of these seaweed mats – under normal conditions – are wonderlands of life, as every offshore fisherman knows.

The evolution of the Gulf Loop Current from a strong downstream delivery phase on May 7 to a cutoff eddy phase on June 11, temporarily detaining oil pollution. Credit: NWS.

The Gulf Loop Current – a term now commonplace– is a superhighway in the sea for spawned babies of giant tunas, swordfish and other billfishes, groupers, snappers and other reef fishes, and even for hatchling turtles. These creatures ride the current —our version of Nemo’s East Australian Current— toward adult habitats, at risk as they pass through the 'kill zone' of oil in the northern Gulf.  

See an animation of the current loop here and see a video of the oil spreading here.

This figure represents the evolution of the Gulf Loop. Credit: NOAA.

Luckily, the chance development on June 1 of a cutoff eddy—a normal phase in the evolution of the Gulf Loop Current, where the current bends deep enough to interact with itself, ultimately cutting off a spinning gyre in the northern Gulf—has delayed the otherwise rapid delivery of oil pollution to the pristine coral reefs, mangrove swamps and seagrass beds of northern Cuba, the Florida Keys and beyond.  Delivery of oil downcurrent to those habitats remains likely, as the Gulf Loop redevelops.  In fact, the weathered oil currently held in the cutoff eddy will likely drift northwest towards the Texas coast.

The beauty, and now oil, down below

An actual track of a sperm whale diving through rich mid-water feeding zones (shown in green) from the northern Gulf of Mexico. Credit: Modified from Azzara, 2006.

Under the surface, hovering clouds of oil pollution drift with the currents, and threaten perhaps the least known elements of this magical world.  At middle depths, a profusion of life – shrimps, lanternfish, jellyfish and squids –create a layer of life so rich it appears as sonar returns to surface ships, earning the name “deep scattering layer” to scientists.  This rarely imagined world of the deep – key prey for surface diving whales, dolphins, sharks and tunas – is now being contaminated twice, as oil pollution rises to and through it, and as sinking particles carry toxicants back downward.  It is no surprise that sperm whales and other deep-feeding life forms we cherish are now numbered among the dead. 

Deepwater treasures contaminated

The Visoca Knoll coral reefs are near the Deepwater Horizon well and are home to a rich variety of life. Credit: Steve W. Ross (UNCW), unpubl. data.

On the bottom, the corals and worms get the short end of the slick.   The deep-origin oil spewing from the crippled well is polluting deepsea wonderlands that are just now being discovered, notably majestic and ancient deepwater coral reefs. The vast majority of the oil that remains in the sea will ultimately find its way to the seafloor, where worms and other sediment-eating life forms will ingest it, be ingested in turn, and continue contaminating food webs – and the very web of life – for generations to come. 

This spill impacts you, too

Put all together, every important part of the broader Gulf of Mexico marine ecosystem – upon which so many people rely for their income, and their way of life – is taking many potential knockout blows.  Productivity of key seafood species could be depressed for years if not generations to come.  Special care will be required to ensure that Gulf seafood remains safe.  There is plenty to cry about, both on the surface and in the unseen places in the deep.

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Ancient Deepwater Coral Ecosystems of the Southeast

Deep water corals - South Atlantic U.S.; Photo by Dr. Steve RossAlthough corals from deepwaters of the U.S. Southeast were first reported way back in the 1880’s, more than a century passed before research revealed the breathtaking scale of the deepwater coral reef ecosystems in the region.  Dr. Steve Ross (UNC-Wilmington) and Dr. John Reed (Harbor Branch) have actively partnered with the South Atlantic Fishery Management Council over the past decade to ensure that cutting-edge science is translated into strong protection for these world class reefs.

These deepwater reef ecosystems include a dizzying array of mounds and pinnacles covering nearly 25,000 square miles from North Carolina to Florida at depths of 1,000 feet and greater on the Blake Plateau and similar geologic contexts, extending into waters managed by the Bahamas and probably Cuba as well. 

Deep water corals - South Atlantic; Photo by Dr. Steve RossThese reefs are home to tremendous biological diversity, including many species new to science, and including species of potential economic value, both for fishing and for pharmaceutical prospecting.  Individual colonies may be thousands of years old, and some mounds likely exceed a million years in age, creating a record of changing conditions in the deep ocean.

The Council’s Habitat and Environmental Protection Advisory Panel (which I chair) and Coral Advisory Panel have worked tirelessly with scientists, the Council, the National Oceanic and Atmospheric Administration and fishermen to create proposed protection zones called “Habitat Areas of Particular Concern,” that will protect these treasures against fishing and other threats.  In particular, EDF negotiated “allowable gear zones,” where traditional fisheries for deepwater animals (golden crab and royal red shrimp) would be allowed, away from vulnerable tall pinnacles.  The Council stands ready to finalize these protection zones at its next meeting in September.

Photos by Dr. Steve Ross

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